Download and compile GL3_parallax_DoF from http://www.autistici.org/encelo/prog_gldemos.php Nothing is displayed in the demo and the following error message is thrown in the terminal: Mesa: User error: GL_INVALID_OPERATION in glUseProgram(program 1 not linked) Mesa: User error: GL_INVALID_OPERATION in glGetUniformLocation(program not linked) With mesa git f9767dac9a06aad93a9d61d108055ad673498bf8 drm git 7080bfdfd9b6c5f003daaef37ae9c329f2d46a6c kernel 3.6.0-rc2 Using HD6950
Created attachment 66199 [details] The culprit shader
When adding more verbosity: Loading shaders/first.frag 0:45(11): error: assignment to read-only variable 'lightDir' error: linking with uncompiled shaderLoading shaders/second.vert
"A varying variable must be written on a vertex shader, where we compute the value of the variable for each vertex. In the fragment shader the variable, whose value results from an interpolation of the vertex values computed previously, can only be read." lightDir is a varying that was write in the vertex shader, so it can only be read in the fragment shader
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