Hi all,
I want to do shadow mapping by doing the depth comparisons myself in
order to implement PCSS. In order to do this I modified the
osgShadow::DebugShadowMap and StandardShadowMap classes to not enable
shadow comparison modes (GL_COMPARE_R_TO_TEXTURE_ARB), and when sampling
the shadow map I get raw depth values, which is what I want.
However, to get the right main pass depth to compare to the shadow map
value, I need to transform the fragment position to light space. To do
this, I've added a uniform that stores the shadow camera's view and
projection matrices, which I set in
StandardShadowMap::aimShadowCastingCamera():
_stateset->getOrCreateUniform("ShadowCameraTransform",
osg::Uniform::FLOAT_MAT4)->set(
view * projection);
Using that matrix, I would have thought in my shader I could do the
following:
uniform mat4 ShadowCameraTransform;
uniform mat4 osg_ViewMatrixInverse;
// ...
varying vec4 lightSpacePos;
void main()
{
// ...
mat4 modelMatrix = osg_ViewMatrixInverse * gl_ModelViewMatrix;
vec4 worldPos = modelMatrix * gl_Vertex;
lightSpacePos = ShadowCameraTransform * worldPos;
// ...
}
And then use that to compare a light-space depth value in the fragment
shader which I could use to compare to the shadow map:
float lightSpaceDepth = (lightSpacePos.xyz / lightSpacePos.w).z;
float shadowMapDepth = texture2D( shadowTexture, uv ).r;
However the lightSpaceDepth value above doesn't seem to be in the right
coordinate space or something, as I get values in too small a range.
I've tried the classic transforms ( * 0.5 + 0.5 or * 2.0 - 1.0) but the
values are still not in the right range.
First of all, am I doing the math right?
Second of all, I left the texture internal format set to
GL_DEPTH_COMPONENT and attached to the DEPTH_BUFFER, assuming that it
was OK, but could that explain my problems? Should I change it to a
general purpose float format (say GL_LUMINANCE32F_ARB), attach it to the
COLOR_BUFFER and write to gl_FragData[0] in the shadow pass's fragment
shader?
Just trying to sanity check a bit :-)
Thanks in advance,
J-S
--
______________________________________________________
Jean-Sebastien Guay [email protected]
http://www.cm-labs.com/
http://whitestar02.webhop.org/
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