Hi Brad -- Is your texture a depth format texture? That is, on the host side, do
you have something like this:
_depthTex = new osg::Texture2D;
_depthTex->setInternalFormat( GL_DEPTH_COMPONENT );
According to the GLSL spec, results from shadow2D and friends is undefined if
the texture is not a depth format.
You'll probably also want to configure shadow comparison, func, and mode, if
you're not already doing that.
-Paul
On 7/7/2011 3:32 AM, Christiansen, Brad wrote:
Hi,
I am implementing some shadows at the moment and have come unstuck with my
understanding of how to sample a shadow texture.
To test my understanding, I implemented what I though shadow2D() would do using
'standard' sampling and a few calculations. This lead to the following code
which works as expected:
varying vec4 projShadow;
uniform sampler2D depthTex;
float val = texture2D(depthTex, projShadow.xy / projShadow.w).r;
float fragDepth = projShadow.z / projShadow.w;
if(val <= fragDepth) {
col = mix(col, vec4(1,0,0,1), 0.3); //shadow
} else {
col = mix(col, vec4(0,1,0,1), 0.3); //lit
}
From my understanding I should be able to replace all this with:
varying vec4 projShadow;
uniform sampler2DShadow depthTex;
float val = shadow2D(depthTex, projShadow.xyz / projShadow.w).r;
or
float val = shadow2DProj(depthTex, projShadow).r;
When I do this I just get garbage.
Given I am getting the correct result with the first approach, and I think the
second should do exactly the same thing, I am stck as to why I cant get shadow
sampling to work correctly. Any suggestions would be greatly appreciated.
Cheers,
Brad
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