Hi guys.
Over the last weeks we encountered some strange black triangles with some of our skinned models under some conditions.
We first thought the graphics card might be the problem or a buggy driver, and the problem persisted and finally I found a repro case (100%) on 3 different machines (NVIDIA Quadroplex, MacBook pro - GL 2.1 under Parallels and GTX 285, all running openSUSE 11.2).
It turned out that there is a problem in Renderer::drawModels (besides the one mentioned here:
http://www.horde3d.org/forums/viewtopic.php?f=3&t=1155.
The actual problem is that the vertex layout is not applied correctly after a shader/material and geometry resource has changed.
This results in calling glDrawRangeElements with the wrong buffers bound and hence wrong vertices / and sometimes complete lock-ups.
Here is the scenario:
Model A: GeoResource GeoA, 1 mesh: Mesh A with Material MatA (Shader S1)
Model B: GeoResource GeoB, 1 mesh: Mesh B with Material MatB (Shader S1)
Model C: GeoResource GeoB, 1 mesh: Mesh B with Material MatB (Shader S1)
Code:
DrawModel call:
Model A:
GeoResource GeoA bound
Mesh A:
- MatA and Shader S1 set
- Vertex layout for GeoA and S1 set
- Draw
Model B:
GeoResource GeoB bound
Mesh B: culled
Model C:
GeoResource GeoB IS NOT re-bound, because already bound
Mesh B:
- MatB and Shader S1 set
! - Vertex layout for GeoB and S1 IS NOT SET, because GeoResource and Shader didn't change since last Draw
! - Draw: now with wrong Vertex Layout / Vertex Buffer combination
So, the simple fix is to add another flag "bool bForceApplyVertexLayout = false;" in line 1545.
Then add this:
Code:
if( curMatRes != meshNode->getMaterialRes() )
{
if( !Modules::renderer().setMaterial( meshNode->getMaterialRes(), shaderContext ) )
{
curMatRes = 0; // because setMaterial has a side-effect: renderer().getCurShader is 0 after it
continue;
}
curMatRes = meshNode->getMaterialRes();
bForceApplyVertexLayout = true; // force re-apply of vertex layout, because shader changed
}
And then
Code:
// Apply vertex layout
if( bForceApplyVertexLayout || curShader != prevShader || curGeoRes != prevGeoRes )
{
if( !Modules::renderer().applyVertexLayout( Modules::renderer()._vlModel ) )
{
Modules::renderer().setShaderComb( 0x0 );
continue;
}
bForceApplyVertexLayout = false;
}
This change will force a re-application of the vertex layout in case a shader did change, which has to be done anyway in that case.
The curShader != prevShader and curGeoRes != prevGeoRes check cannot catch the above mentioned scenario.
I guess one can further simplify the check, but currently no time.
If you need a SVN diff, let me know, although above changes should be ok for the current SVN 243.
Alex
P.S. sorry for lengthy post
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