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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