// draw callback that will tweak the far clipping plane just
// before rendering a drawable.
struct OverrideNearFarValuesCallback : public osg::Drawable::DrawCallback
{
OverrideNearFarValuesCallback(double radius)
: _radius(radius) {}
virtual void drawImplementation(osg::RenderInfo& renderInfo,
const osg::Drawable* drawable) const
{
osg::Camera* currentCamera = renderInfo.getCurrentCamera();
if (currentCamera)
{
// Get the current camera position.
osg::Vec3 eye, center, up;
renderInfo.getCurrentCamera()->getViewMatrixAsLookAt( eye, center, up);
// Get the max distance we need the far plane to be at,
// which is the distance between the eye and the origin
// plus the distant from the origin to the object (star sphere
// radius, sun distance etc), and then some.
double distance = eye.length() + _radius*2;
// Save old values.
osg::ref_ptr<osg::RefMatrixd> oldProjectionMatrix = new osg::RefMatrix;
oldProjectionMatrix->set( renderInfo.getState()->getProjectionMatrix());
// Get the individual values
double left, right, bottom, top, zNear, zFar;
oldProjectionMatrix->getFrustum( left, right, bottom, top, zNear, zFar);
// Build a new projection matrix with a modified far plane
osg::ref_ptr<osg::RefMatrixd> projectionMatrix = new osg::RefMatrix;
projectionMatrix->makeFrustum( left, right, bottom, top, zNear, distance );
renderInfo.getState()->applyProjectionMatrix( projectionMatrix.get());
// Draw the drawable
drawable->drawImplementation(renderInfo);
// Reset the far plane to the old value.
renderInfo.getState()->applyProjectionMatrix( oldProjectionMatrix.get() );
}
else
{
drawable->drawImplementation(renderInfo);
}
}
double _radius;
};
struct AddCallbackToDrawablesVisitor : public osg::NodeVisitor
{
AddCallbackToDrawablesVisitor(double radius)
: osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN),
_radius(radius) {}
virtual void apply(osg::Geode& node)
{
for (unsigned int i = 0; i < node.getNumDrawables(); i++)
{
node.getDrawable(i)->setDrawCallback( new OverrideNearFarValuesCallback(_radius) );
// Do not use display lists otherwise the callback will only
// be called once on initial compile.
node.getDrawable(i)->setUseDisplayList(false);
}
}
double _radius;
};
调用
***********************************************
AddCallbackToDrawablesVisitor visitor( mpr_innerRadius );
geode->accept( visitor );
**********************************************
怎样在osg中动态的设置drawable的最近最远裁剪面