It will be intersting to add a procedure like glCheckVisibilityf ( GLfloat pmin, GLfloat pmax ), in which you pass the max and min bbox’s points in world space and returns if visible or not using Z-buffer, A-buffer, frustum culling, etc… using total hardware acceleration, like HP Visualize FX.
Definitely a cool feature. I know HP has an extension for that called HP_occlusion something which basically renders without writing in the frame buffer and returns if all the fragments failed the depth test between the start of the command and the end. Intense3D cards implement the extension.
Sounds like powerVR consumer cards could support that extension if they did a decent openGL driver but I guess that is too much too ask? Maybe in their new hardware T&L card? Please? Oh come on…
But seriously, since most cards can transform way more geometry than they can draw it is going to become inevitable that they will need to include better culling than just the behind-the-scenes-Z-buffer.
[This message has been edited by foobar (edited 09-18-2000).]