Additional questions: 1) Why shadowPassCamera->setClearColor(osg::Vec4f(1000.0f, 0.0f, 0.0f, 1.0f))? 2) Why length() in all the shadow related shader code?
2013/10/12 michael kapelko <[email protected]> > Thanks for the example. I've forked it and playing with it now to find out > the difference. > Why is there only shadow when I use light directions of (0, 0.8, 1), (0, > 0.0001, 1), but not when I try (0, 0, 1)? > That's the direction I use for my own example. > Thanks. > > > 2013/10/11 Marcel Pursche <[email protected]> > >> Hi, >> >> shadow mapping is a projective texturing approach. A good methaphor to >> explain it is that from the light source a slide projector is casting the >> depth buffer on your scene. For this to work you need to do two things: >> 1. create your depth buffer with screenspace coordinates(the screenspace >> of the shadow camera) >> 2. Pass the view projection matrix of your shadow pass to the main pass >> and use it to project the world coordinates of your scene into screenspace >> coordinates of the shadow camera. The projected coordinates can then be >> used as texture coordinates for your depth buffer. >> I have written a very basic shadow mapping example: >> https://github.com/MPursche/3dcgtutorials/tree/master/03_ShadowMapping >> It uses a GL_R32F depth buffer(I wanted to evaluate the performance >> against a regular depth buffer). It uses forward shading but I hope you can >> apply the principle on your deferred shading renderer. >> >> Here is the part where I calculate the shadow matrix for the main pass: >> >> Code: >> >> osg::Matrixd shadowMatrix = viewMatrix * projectionMatrix * >> osg::Matrixd::translate(1.0, 1.0, 1.0) * osg::Matrixd::scale(0.5, 0.5, 0.5); >> >> >> >> The translation and scale at the end is to come from [-1,1] coordinates >> to [0,1] coordinates. >> >> You just need to do the following, to compute the texture coordinates for >> your depth texture: >> >> Code: >> >> gl_TexCoord[0] = shadowMatrix * gl_Vertex; // insert modelMatrix here if >> necessary -> shadowMatrix * modelMatrix * gl_Vertex >> >> >> >> >> This is how my fetch in the shader looks like: >> >> Code: >> >> float depth = texture2D(depthTexture, gl_TexCoord[0].st).x; >> float visibility = (shadowDepth <= (depth + 0.1)) ? 1.0 : 0.0; >> >> >> >> >> Thank you! >> >> Cheers, >> Marcel >> >> ------------------ >> Read this topic online here: >> http://forum.openscenegraph.org/viewtopic.php?p=56749#56749 >> >> >> >> >> >> _______________________________________________ >> osg-users mailing list >> [email protected] >> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org >> > >
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