diff --git a/include/osg/ClusterCullingCallback b/include/osg/ClusterCullingCallback index a31f2bdeb..0091bb183 100644 --- a/include/osg/ClusterCullingCallback +++ b/include/osg/ClusterCullingCallback @@ -19,8 +19,31 @@ namespace osg { -/** Implements cluster culling to cull back facing drawables. Derived from - * Drawable::CullCallback. +/** @class ClusterCullingCallback + @brief Implements cluster culling to cull back facing subgraphs and drawables. Derived from Drawable::CullCallback and osg::NodeCallback. + + This culling callback is intended to be attached to a node using the setCullCallback method. If the + node is a drawable cull(osg::NodeVisitor*, osg::Drawable*, osg::State*) otherwise + operator()(Node*, NodeVisitor*) will be called during the cull traversal. + + To decide whether the node (in case of a drawable) or its children (in case of any other node type) are + to be culled depends on four parameters: + - a control point, + - a normal specified at the control point, + - a deviation value representing the cosinus of an enclosed angle and + - a radius describing a sphere around the control point. + + The node is culled if the following two conditions are fulfilled: + - the distance between the current eye/view point to the control point is larger or equal to radius, + - the cosinus of the enclosed angle between the normal and the vector from the control point to the eye/view point + is smaller(!) than the specified deviation value (normally this value is negative meaning that the enclosed angle + between the control point and the eye/view point is larger than the angle indirectly specified by the + deviation value). + + @remark As the deviation is representing the cosine of an enclosed angle its value should be within the + the interval [-1; 1]. A value of one will cull all nodes while a value of -1 will never cull a node. + The deviation will normally have negative values because then the enclosed angle between the normal and the + eye/view point is larger than 90 degrees (and therefore the eye sees the "back" from the control point). */ class OSG_EXPORT ClusterCullingCallback : public DrawableCullCallback, public NodeCallback {