I expect this already exists but I cam up with it yesterday while thinking about something else. In an engine using a quadtree / octree, could the quadtree / octree segments cast volume shadows using the camera position & look as the light source? Then the segments could be tested to see if thy lie completely within a shadow of another segment : not visible. Now this is why I thought it could be feasibile. The further away a segment is, the larger it''ll be : larger segments will only be drawn if they are far enough away from the camera to fit entirely in to the view frustum. So although this check would not be accurate against the geometry, it would be fast and might be suitable. As the segments get smaller, they "hug" the geometry more so the shadow test becomes more accurate. This could be extended so that at a certain size of segment the polygons contained within the segment cast the shadow volumes instead of the segment itself. Does this exist allready? If it doesn''t, what do you think? Matt