http://bitwiseor.com Just another WordPress weblog Mon, 14 Aug 2006 15:46:36 -0400 http://wordpress.org/?v=2.8.4 hourly 1 http://bitwiseor.com/gl_arb_shadow/comment-page-1/#comment-25 » OpenGL Transforms and the Inverse Model View Mon, 14 Aug 2006 15:46:36 +0000 http://blog.bitwiseor.com/gl_arb_shadow/#comment-25 [...] It is important to realise that OpenGL’s Model View matrix is actually M * C, so, if we want to get the position of the vertex in world space, we will have to use the modelview matrix to go to camera space, then multiply by C-1 (the inverse of the camera matrix). This gives us V * M * C * C-1 = V * gl_ModelViewMatrix * C-1 = V * M. And world space is exactly what we need to do shadow mapping, refraction, reflectiona and a plethora of other things. OpenGL took care of this for us with the GL_ARB_Shadow extension. By using glTexGen, OpenGL computes the inverse camera matrix and applies it without us having to fuss with inverses. But, now we’ll need to do an inverse ourselves. [...] [...] It is important to realise that OpenGL’s Model View matrix is actually M * C, so, if we want to get the position of the vertex in world space, we will have to use the modelview matrix to go to camera space, then multiply by C-1 (the inverse of the camera matrix). This gives us V * M * C * C-1 = V * gl_ModelViewMatrix * C-1 = V * M. And world space is exactly what we need to do shadow mapping, refraction, reflectiona and a plethora of other things. OpenGL took care of this for us with the GL_ARB_Shadow extension. By using glTexGen, OpenGL computes the inverse camera matrix and applies it without us having to fuss with inverses. But, now we’ll need to do an inverse ourselves. [...]

]]> http://bitwiseor.com/gl_arb_shadow/comment-page-1/#comment-24 BitwiseOR » GL_ARB_shadow_funcs Tue, 10 Jan 2006 21:10:04 +0000 http://blog.bitwiseor.com/gl_arb_shadow/#comment-24 [...] The GL_ARB_shadow_funcs extension requires GL_ARB_shadow and GL_ARB_depth_texture in order to have any effect. In the GL_ARB_shadow example on this site we use GL_LEQUAL when setting the GL_TEXTURE_COMPARE_FUNC_ARB texture parameter. GL_ARB_shadow allows this comparison function to be GL_GEQUAL as well, but not any of the other comparison functions. [...] [...] The GL_ARB_shadow_funcs extension requires GL_ARB_shadow and GL_ARB_depth_texture in order to have any effect. In the GL_ARB_shadow example on this site we use GL_LEQUAL when setting the GL_TEXTURE_COMPARE_FUNC_ARB texture parameter. GL_ARB_shadow allows this comparison function to be GL_GEQUAL as well, but not any of the other comparison functions. [...]

]]>