oe中的視角加速感受好奇怪，就仿照谷歌方式去改了。html
先看看oe原來的漫遊器改變視角的接口：node
void CameraManipulator::setViewpoint(const Viewpoint& vp, double duration_seconds) { // If the manip is not set up, save the viewpoint for later. if ( !established() ) { _pendingViewpoint = vp; _pendingViewpointDuration.set(duration_seconds, Units::SECONDS); } else { // Save any existing tether node so we can properly invoke the callback. osg::ref_ptr<osg::Node> oldEndNode; if ( isTethering() && _tetherCallback.valid() ) _setVP1->getNode(oldEndNode); // starting viewpoint; all fields will be set: _setVP0 = getViewpoint(); // ending viewpoint _setVP1 = vp; // Reset the tethering offset quat. _tetherRotationVP0 = _tetherRotation; _tetherRotationVP1 = osg::Quat(); // Fill in any missing end-point data with defaults matching the current camera setup. // Then all fields are guaranteed to contain usable data during transition. double defPitch, defAzim; getEulerAngles( _rotation, &defAzim, &defPitch ); if ( !_setVP1->heading().isSet() ) _setVP1->heading() = Angle(defAzim, Units::RADIANS); if ( !_setVP1->pitch().isSet() ) _setVP1->pitch() = Angle(defPitch, Units::RADIANS); if ( !_setVP1->range().isSet() ) _setVP1->range() = Distance(_distance, Units::METERS); if ( !_setVP1->nodeIsSet() && !_setVP1->focalPoint().isSet() ) { osg::ref_ptr<osg::Node> safeNode; if ( _setVP0->getNode( safeNode ) ) _setVP1->setNode( safeNode.get() ); else _setVP1->focalPoint() = _setVP0->focalPoint().get(); } _setVPDuration.set( std::max(duration_seconds, 0.0), Units::SECONDS ); OE_DEBUG << LC << "setViewpoint:\n" << " from " << _setVP0->toString() << "\n" << " to " << _setVP1->toString() << "\n"; // access the new tether node if it exists: osg::ref_ptr<osg::Node> endNode; _setVP1->getNode(endNode); // Timed transition, we need to calculate some things: if ( duration_seconds > 0.0 ) { // Start point is the current manipulator center: osg::Vec3d startWorld; osg::ref_ptr<osg::Node> startNode; startWorld = _setVP0->getNode(startNode) ? computeWorld(startNode.get()) : _center; _setVPStartTime.unset(); // End point is the world coordinates of the target viewpoint: osg::Vec3d endWorld; if ( endNode.valid() ) endWorld = computeWorld(endNode.get()); else _setVP1->focalPoint()->transform( _srs.get() ).toWorld(endWorld); // calculate an acceleration factor based on the Z differential. _setVPArcHeight = 0.0; double range0 = _setVP0->range()->as(Units::METERS); double range1 = _setVP1->range()->as(Units::METERS); double pitch0 = _setVP0->pitch()->as(Units::RADIANS); double pitch1 = _setVP1->pitch()->as(Units::RADIANS); double h0 = range0 * sin( -pitch0 ); double h1 = range1 * sin( -pitch1 ); double dh = (h1 - h0); // calculate the total distance the focal point will travel and derive an arc height: double de = (endWorld - startWorld).length(); // maximum height during viewpoint transition if ( _settings->getArcViewpointTransitions() ) { _setVPArcHeight = osg::maximum( de - fabs(dh), 0.0 ); } // calculate acceleration coefficients if ( _setVPArcHeight > 0.0 ) { // if we're arcing, we need seperate coefficients for the up and down stages double h_apex = 2.0*(h0+h1) + _setVPArcHeight; double dh2_up = fabs(h_apex - h0)/100000.0; _setVPAccel = log10( dh2_up ); double dh2_down = fabs(h_apex - h1)/100000.0; _setVPAccel2 = -log10( dh2_down ); } else { // on arc => simple unidirectional acceleration: double dh2 = (h1 - h0)/100000.0; _setVPAccel = fabs(dh2) <= 1.0? 0.0 : dh2 > 0.0? log10( dh2 ) : -log10( -dh2 ); if ( fabs( _setVPAccel ) < 1.0 ) _setVPAccel = 0.0; } // Adjust the duration if necessary. if ( _settings->getAutoViewpointDurationEnabled() ) { double maxDistance = _srs->getEllipsoid()->getRadiusEquator(); double ratio = osg::clampBetween( de/maxDistance, 0.0, 1.0 ); ratio = accelerationInterp( ratio, -4.5 ); double minDur, maxDur; _settings->getAutoViewpointDurationLimits( minDur, maxDur ); _setVPDuration.set( minDur + ratio*(maxDur-minDur), Units::SECONDS ); } } else { // Immediate transition? Just do it now. _setVPStartTime->set( _time_s_now, Units::SECONDS ); setViewpointFrame( _time_s_now ); } // Fire a tether callback if required. if ( _tetherCallback.valid() ) { // starting a tether to a NEW node: if ( isTethering() && oldEndNode.get() != endNode.get() ) (*_tetherCallback)( endNode.get() ); // breaking a tether: else if ( !isTethering() && oldEndNode.valid() ) (*_tetherCallback)( 0L ); } } // reset other global state flags. _thrown = false; _task->_type = TASK_NONE; }
這裏有幾個重點參數：ui
osgEarth::optional<osgEarth::Viewpoint> _setVP0和_setVP1 ：開始視點，結束視點url
double _setVPAccel, _setVPAccel2; 開始點去最高點加速度，最高點去結束點加速度spa