OpenGL超級寶典筆記——畫三角形

<p>學習了畫線的知識，咱們可使用GL_LINE_LOOP來畫閉合的多邊形。可是使用這種方式畫出來的只有線框，多邊形沒有填充顏色。OpenGL支持繪製實心的多邊形，並使用當前的顏色進行填充。</p> <h3>三角形</h3> <p>簡單的三角形，須要指定三個頂點。</p> <div id="codeSnippetWrapper"> <div style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px" id="codeSnippet"><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum1"> 1:</span> glBegin(GL_TRIANGLES);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum2"> 2:</span> glVertex2f(0.0f, 0.0f); <span style="color: #008000">// V0</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum3"> 3:</span> glVertex2f(25.0f, 25.0f); <span style="color: #008000">// V1</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum4"> 4:</span> glVertex2f(50.0f, 0.0f); <span style="color: #008000">// V2</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum5"> 5:</span> glVertex2f(-50.0f, 0.0f); <span style="color: #008000">// V3</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum6"> 6:</span> glVertex2f(-75.0f, 50.0f); <span style="color: #008000">// V4</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum7"> 7:</span> glVertex2f(-25.0f, 0.0f); <span style="color: #008000">// V5</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum8"> 8:</span> glEnd();</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum9"> 9:</span>&nbsp; </pre><!--CRLF--></div></div> <p>這兩個三角形會使用當前的顏色進行填充。</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221757_PrI7.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221757_1wmE.png" width="695" height="278"></a></p> <h3>多邊形的環繞</h3> <p>按照頂點指定的順序和方向組合稱爲環繞。上圖的兩個多邊形是順時針環繞的。咱們能夠經過改變頂點的順序，從而改變環繞方向。咱們把v4和v5的順序調換過來，則這個三角形的環繞方向爲逆時針了。</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221801_w510.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221802_u7FX.png" width="706" height="323"></a></p> <p>OpenGL默認是逆時針環繞方向爲正方向，即逆時針環繞的三角形爲正面。上圖左邊的三角形，顯示的是正面，而右邊的顯示的是反面。咱們也能夠經過函數glFrontFace(GL_CW);來告訴OpenGL順時針環繞的多邊形是正面。環繞方向是多邊形一個很是有用的性質，能夠用於消除沒必要要的面。</p>

<h3>三角形帶</h3> <p>咱們能夠繪製多個三角形連起來造成多個面或者多邊形。使用GL_TRIANGLE_STRIP圖元，能夠繪製一串相連的多邊形，來節省大量的時間。</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221803_j1pG.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221803_eppo.png" width="735" height="287"></a></p> <p>由上圖能夠看到，多邊形的邊的繪製順序並非徹底按照咱們指定的頂點順序的。而是按照OpenGL指定的順序逆時針方向繪製的。</p> <p>使用三角形帶而不是分別指定每一個三角形的頂點的優點有兩個：</p> <ol> <li>用前面三個頂點指定一個三角形後，只需再指定一個頂點就能畫出第二個三角形。要繪製大量的三角形時，這種方法能夠節省大量的代碼以及數據存儲空間</li> <li>運算性能的提升和帶寬的節省。更少的頂點，從內存傳輸的顯卡的時間更快，以及參與變換的頂點更少。</li></ol> <h3>三角形扇</h3> <p>除了三角形帶以外，咱們還能夠經過GL_TRIANGLE_FAN圖元，建立一組圍繞一箇中心點的三角形扇。經過制定5個頂點咱們就能夠繪製3個三角形來造成三角形扇。用3個頂點指定一個三角形後，後續的頂點Vn與原點V0以及前面的一個頂點Vn-1造成一個三角形。</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221804_x6Y0.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221805_6EHL.png" width="756" height="327"></a></p> <h3>建立實心物體</h3> <div id="codeSnippetWrapper"> <div style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px" id="codeSnippet"><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum1"> 1:</span> <span style="color: #0000ff">static</span> <span style="color: #0000ff">void</span> RenderScene()</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum2"> 2:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum3"> 3:</span> <span style="color: #008000">//清除顏色緩衝區和深度緩衝區</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum4"> 4:</span> glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum5"> 5:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum6"> 6:</span> GLfloat x, y, z, angle;</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum7"> 7:</span> <span style="color: #008000">//用於顏色判斷</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum8"> 8:</span> <span style="color: #0000ff">bool</span> color;</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum9"> 9:</span> glColor3f(1.0f, 1.0f, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum10"> 10:</span> <span style="color: #008000">//是否開啓深度緩衝</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum11"> 11:</span> <span style="color: #0000ff">if</span> (bDepth)</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum12"> 12:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum13"> 13:</span> glEnable(GL_DEPTH_TEST);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum14"> 14:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum15"> 15:</span> <span style="color: #0000ff">else</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum16"> 16:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum17"> 17:</span> glDisable(GL_DEPTH_TEST);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum18"> 18:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum19"> 19:</span> <span style="color: #008000">//是否開啓隱藏面消除</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum20"> 20:</span> <span style="color: #0000ff">if</span> (bCull)</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum21"> 21:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum22"> 22:</span> glEnable(GL_CULL_FACE);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum23"> 23:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum24"> 24:</span> <span style="color: #0000ff">else</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum25"> 25:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum26"> 26:</span> glDisable(GL_CULL_FACE);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum27"> 27:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum28"> 28:</span> <span style="color: #008000">//開啓線框模式 </span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum29"> 29:</span> <span style="color: #0000ff">if</span> (bOutLine)</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum30"> 30:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum31"> 31:</span> glPolygonMode(GL_BACK, GL_LINE) ;</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum32"> 32:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum33"> 33:</span> <span style="color: #0000ff">else</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum34"> 34:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum35"> 35:</span> glPolygonMode(GL_BACK, GL_FILL);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum36"> 36:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum37"> 37:</span> </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum38"> 38:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum39"> 39:</span> glPushMatrix();</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum40"> 40:</span> glRotatef(xRot, 1.0f, 0.0f, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum41"> 41:</span> glRotatef(yRot, 0.0f, 1.0f, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum42"> 42:</span> <span style="color: #008000">//畫椎體</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum43"> 43:</span> glBegin(GL_TRIANGLE_FAN);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum44"> 44:</span> glVertex3f(0.0f, 0.0f, 70.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum45"> 45:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum46"> 46:</span> <span style="color: #0000ff">for</span> (angle = 0.0f; angle &lt;= (2 * GL_PI); angle += (GL_PI / 8))</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum47"> 47:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum48"> 48:</span> x = 50.0f * sin(angle);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum49"> 49:</span> y = 50.0f * cos(angle);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum50"> 50:</span> color = !color;</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum51"> 51:</span> </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum52"> 52:</span> glVertex3f(x, y, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum53"> 53:</span> <span style="color: #0000ff">if</span>(color)</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum54"> 54:</span> glColor3f(1.0f, 0.0f, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum55"> 55:</span> <span style="color: #0000ff">else</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum56"> 56:</span> glColor3f(0.0f, 1.0f, 1.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum57"> 57:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum58"> 58:</span> glEnd();</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum59"> 59:</span> <span style="color: #008000">//畫椎體的底面</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum60"> 60:</span> glBegin(GL_TRIANGLE_FAN);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum61"> 61:</span> glVertex2f(0.0f, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum62"> 62:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum63"> 63:</span> <span style="color: #0000ff">for</span> (angle = 0.0f; angle &lt;= (2 * GL_PI); angle += (GL_PI / 8))</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum64"> 64:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum65"> 65:</span> x = 50.0f * sin(angle);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum66"> 66:</span> y = 50.0f * cos(angle);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum67"> 67:</span> color = !color;</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum68"> 68:</span> </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum69"> 69:</span> glVertex2f(x, y);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum70"> 70:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum71"> 71:</span> <span style="color: #0000ff">if</span>(color)</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum72"> 72:</span> glColor3f(1.0f, 0.0f, 0.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum73"> 73:</span> <span style="color: #0000ff">else</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum74"> 74:</span> glColor3f(0.0f, 1.0f, 1.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum75"> 75:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum76"> 76:</span> glEnd();</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum77"> 77:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum78"> 78:</span> glPopMatrix();</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum79"> 79:</span> glutSwapBuffers();</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum80"> 80:</span> }</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum81"> 81:</span>&nbsp; </pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum82"> 82:</span> <span style="color: #0000ff">static</span> <span style="color: #0000ff">void</span> SetupRC()</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum83"> 83:</span> {</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum84"> 84:</span> glClearColor(0.0f, 0.0f, 0.0f, 1.0f);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum85"> 85:</span> <span style="color: #008000">//設置環繞方向</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum86"> 86:</span> glEnable(GL_CW);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum87"> 87:</span> <span style="color: #008000">//設置填充模式</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum88"> 88:</span> glShadeModel(GL_FLAT);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum89"> 89:</span> <span style="color: #008000">//設置要消除的隱藏面，這裏設置爲反面</span></pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum90"> 90:</span> glCullFace(GL_BACK);</pre><!--CRLF--><pre style="border-bottom-style: none; text-align: left; padding-bottom: 0px; line-height: 12pt; border-right-style: none; background-color: #f4f4f4; margin: 0em; padding-left: 0px; width: 100%; padding-right: 0px; font-family: 'Courier New', courier, monospace; direction: ltr; border-top-style: none; color: black; font-size: 8pt; border-left-style: none; overflow: visible; padding-top: 0px"><span style="color: #606060" id="lnum91"> 91:</span> }</pre><!--CRLF--></div></div> <p><a href="http://static.oschina.net/uploads/img/201309/12221805_yX6n.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221805_3RWT.png" width="355" height="346"></a></p> <p>使用紅青相間的方式來繪製一個錐體。</p> <h3>設置多邊形的顏色</h3> <p>多邊形的填充模式有兩種一種是單調着色GL_FLAT,一種平滑着色GL_SMOOTH。</p> <p>經過glShadeMode(GL_FLAT);和glShadeMode(GL_SMOOTH);來設置。單調着色以三角形的最後一個頂點的顏色來填充三角形。平滑着色則是用三個頂點的顏色值進行內插值運算，來填充三角形的顏色。</p> <p>平滑着色效果以下：</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221806_4G1w.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221806_F1HD.png" width="216" height="244"></a></p> <h3>隱藏面消除</h3> <p>若是沒有使用深度緩衝區，來進行深度測試。上面的椎體如何旋轉（經過方向鍵能夠旋轉），都是把底面顯示了出來。由於底面咱們是在後面畫的，最後一個繪製的物體出如今以前繪製的物體的前面。若是開啓了深度測試來解決問題。</p> <p>深度測試：當一個像素被繪製時，它將被設置一個值（z值），以表示它和觀測者的距離。之後當這個位置要繪製新像素時，新像素的z值就會和舊像素的z值進行比較。若是新像素z值更高，則更靠近觀察者，則應該被繪製，反之被忽略。</p> <p>啓用深度測試只須調用glEnable(GL_DEPTH_TEST);每次場景被渲染以前，應該清楚深度緩衝區，與清楚顏色緩衝區相似。</p> <p>glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);</p> <p>在程序用使用右鍵點擊，彈出菜單，深度測試來切換深度測試。在繪製3D實體時，深度測試每每是必須的。</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221807_WGfL.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221808_149M.png" width="462" height="372"></a></p> <h3>剔除</h3> <p> <p>雖然啓用深度測試，能夠消除隱藏面。但不少時候，咱們清楚那些面是不須要繪製，應該被剔除的。例如：多邊形的背面不該該被顯示。若是咱們告知OpenGL這個圖形面不須要被繪製，就不會把這個圖形發送給OpenGL驅動程序和硬件，能夠提升性能。</p> <p>啓用剔除面的功能。</p> <p>//指定順時針環繞的面爲正面</p> <p>glFrontFace(GL_CW);</p> <p>//開啓剔除面，剔除背面。</p> <p>glEnable(GL_CULL_FACE);</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221810_vOrX.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221810_PD0k.png" width="800" height="561"></a></p> <p><a href="http://static.oschina.net/uploads/img/201309/12221811_0o8h.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221811_sf6H.png" width="390" height="313"></a></p> <p>錐體的底面面向錐體內部的是正面。要改變底面的正面，能夠再繪製底面時設置glFrontFace(GL_CCW);</p> <h3>多邊形模式</h3> <p>多邊形咱們能夠指定它的模式，要填充仍是隻畫線框或者只畫頂點。</p> <p>經過glPolygonMode(GL_BACK, GL_LINE) ;設置多邊形的背面只畫線。</p> <p>經過glPolygonMode(GL_BACK, GL_FILL) ;設置多邊形的背面爲實體。</p></p>

<p>經過glPolygonMode(GL_BACK, GL_POINT) ;設置多邊形的背面只畫點。</p> <p><a href="http://static.oschina.net/uploads/img/201309/12221814_SVjB.png"><img style="background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; display: inline; border-top: 0px; border-right: 0px; padding-top: 0px" title="image" border="0" alt="image" src="http://static.oschina.net/uploads/img/201309/12221814_4HTn.png" width="244" height="242"></a></p> <p>源代碼：<a href="https://github.com/sweetdark/openglex/tree/master/triangle">https://github.com/sweetdark/openglex/tree/master/triangle</a></p>