Hi, it is a bit complex to explain in detail how the projection matrix transforms depth values. In short: the depth is linearized to [0,1] with the near and far plane and after this multiplied with a depth-dependent factor, so that near values take up more space in the depth range than far away values. This is necessary to use the limited precission of the depth buffer for fragments that a closer to the viewer. This is how a regular depth buffer would work. But in my implementation with the color buffer the depth values are stored in [0,far] range. To get this values I simply multiply each vertex with the modelViewMatrix and use the negative z component:
Code: float depth = -(gl_modelViewMatrix * gl_Vertex).z; If you want to get the same depth value in your second pass you need to calculate the following: Code: float depth = -(shadowViewMatrix * p_worldspace).z; So you need to pass the shadowProjectionMatrix and the shadowViewMatrix to the shader. To sum things up this is how you calculate your texture coordinate and your depth to test against: Code: vec2 shadowTexCoord = (shadowViewProjectionMatrix * p_worldspace).st; float fragmentDepth = -(shadowViewMatrix * p_worldspace).z; Your shadowViewProjectionMatrix should consist of: Code: osg::Matrixd shadowViewProjectionMatrix = shadowViewMatrix * shadowProjectionMatrix * osg::Matrixd::translate(1.0, 1.0, 1.0) * osg::Matrixd::scale(0.5, 0.5, 0.5); Thank you! Cheers, Marcel ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=56828#56828 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
