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Min-Max mipmap

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Hi all, I'm trying to generate a hierarchical shadow map (HSM), that is, a min-max mipmap, but need some help. I generate my usual shadow map with this call: glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32, 0, 0, shadowWidth, shadowHeight, 0); But now I want to adapt it so it generates a HSM instead, and need some pointers. This is my attempted code thus far: glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT32, // base level the same as the full shadow map 0, 0, shadowSize, shadowSize, 0); for(i = 1; pow(2,i) == shadowSize; i++) // for level i of the mipmap { glBlendEquationEXT(GL_MAX_EXT); // use max blend glCopyTexImage2D(GL_TEXTURE_2D, i, GL_DEPTH_COMPONENT32, 0, 0, shadowSize/pow(2,i), shadowSize/pow(2,i), 0); glBlendEquationEXT(GL_MIN_EXT); // use min blend // unsure how to store minimum value on separate channel } glBlendEquationEXT(GL_FUNC_ADD_EXT); // restore standard blend mode I don't know how to manipulate the colour channels of the mipmap directly as I use glCopyTexImage2D to read directly from the depth buffer. Any help is greatly appreciated, thanks in advance!

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