public void SetActiveGeometryShader( GLSLGpuProgram geometryProgram )
{
if (geometryProgram != activeGeometryProgram)
{
activeGeometryProgram = geometryProgram;
// active link program is no longer valid
activeLinkProgram = null;
// change back to fixed pipeline
Gl.glUseProgramObjectARB( 0 );
}
}