In my own experiments with the GLSL grid patch I've been seeing lots
of visual artefacts and quite a few complete system lockups requiring
hard reboot (iMac with nvidia GeForce 8800 GS gfx card). It does seem
intermittent though with the script working fine for a while and then
not at all even without any code changes.
At first I thought it was some odd issues with my fragment shader but
switching out the GLSL grid patch for a standard sprite seems patch
seems to have sorted my problem for the moment.
I'll post an example when I've investigated it a little further.
--
Tom Beddard
http://www.subblue.com
On 5 Sep 2009, at 04:39, Christopher Wright wrote:
Spent some time with the GLSL shader today, had some annoying
problems pop up.
This composition demonstrates 3 such problems, described in Root-
level notes.
<many issues.qtz>
Issue 1: The GLSL Grid is incorrectly assumed to always be from -
width/2, -height/2 to +width/2,+height/2 (z=0). Because of this, it
is incorrectly not rendered when QC deems it to be off screen.
However, Vertex Shaders can deform vertices such that the grid _is_
on screen, even when its original vertices aren't.
Issue 2: The billboard patch casts an incorrect shadow on the
sphere -- I'm not entirely sure what's going on there, and will
probably need to investigate this further.
Issue 3: The lighting patch renders an impostor-shadow where the
GLSL grid's original (non-deformed) vertices are. However, if the
vertices are deformed, the shadow is still rendered in space where
the grid was. In comical cases (i.e. output vertex = input vertex -
2 on the z axis), the shadow can even end up being rendered in
space. (In this example, the grid is rippled with sine waves, yet
the shadow remains planar, which is wrong.)
Can anyone confirm/flesh out these (for a more detailed bug report/
bug report set)?
--
[ christopher wright ]
[email protected]
http://kineme.net/
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