Hi Paul, On 12/11/06, Paul Martz <[EMAIL PROTECTED]> wrote:
I think (hope) the occlusion query should not flush the rendering pipeline like glReadPixels. glReadPixels absolutely clears the contents of the rendering pipeline in order to retrieve the results. Occlusion query, on the other hand, allows the pipeline to stay full while results are retrieved. If you use the feature correctly, you're subject to the inherent roundtrip and readback latency, but shouldn't experience the latency associated with filling an empty rendering pipe after the results are retrieved. (Warning: apps can abuse this feature. If you issue a query and immediately block for the results, then yes, that will completely flush the pipe.)
I would expect the occlussion querry will be similiar to glReadPixels as for both you have to flush the contents of the OpenGL fifo in front OpenGL call to retrieving the results, the only way to avoid this is to not querry for the results time after most the frame has been drawn. If the special effect that requires the pixel coverage count can be drawn after then rest of the scene then potentially things will might be doable within one frame. Robert. _______________________________________________ osg-users mailing list [email protected] http://openscenegraph.net/mailman/listinfo/osg-users http://www.openscenegraph.org/
