From: Allan Schaffer (allan++at++sgi.com)
Date: 03/16/2000 14:09:50
On Mar 15, 11:08pm, Thomas Ruge wrote:
>
> I think one important point is how your 3
> channels are oriented, if your viewpoints are positioned that the 3
> view frustums see almost the whole Scene, then the machine has to
> render almost all polygons of the scene and view frustum culling
> doesnt help to reduce the number of rendered polygons.
No, that's not accurate. Despite the supposition of a wide FOV, view
frustum culling is still helping a _lot_ there, because each channel
is culled to its own frustum. There's no 'combinatory frustum'
created for multiple channels or anything along those lines.
Let's say each of the three channels have a 60 degree horizontal FOV
(total 180 deg). Without view frustum culling EACH of those three
channels would draw the entire scene graph. With view frustum
culling on each channel only draws objects within its own frustum.
Even if you had six 60-degree-wide channels representing a 360 degree
total field of view the same principle would still hold true -- view
frustum culling would only select objects within the per-channel
frustum to be drawn. You might be thinking that 360 degrees would
now mean that _some_ channel is adding it's 60-degree slice of the
total database onto the graphics pipe's rendering load -- but don't
forget about the vertical FOV, and perhaps more importantly, that far
clip plane..
Allan
-- Allan Schaffer allan++at++sgi.com Silicon Graphics http://reality.sgi.com/allan
This archive was generated by hypermail 2b29 : Thu Mar 16 2000 - 14:10:00 PST