More sophisticated implementations of percentage closer filtering (PCF) take into account the relative distance between the light and the shadow versus the light and the occluder. Doing this can make soft shadows more realistic, by allowing their penumbra to change in size as the light moves closer or further from the occluder (or as the occluder moves closer or further from the shadow). Study existing methods for incorporating this capability, and add it to Program 8.2.

Program 8.2 

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Fragment Shader #version 430 // all variable declarations are unchanged // Returns the shadow depth value for a texel at distance (x,y) from shadow_coord. Recall that // shadow_coord is the location in the shadow map corresponding to the current pixel being rendered. float lookup(float ox, float oy) {float t = textureProj(shadow Tex, shadow_coord + vec4(ox * 0.001 * shadow_coord.w, oy * 0.001 * shadow_coord.w, -0.01, 0.0)); // the third parameter (-0.01) is an offset to counteract shadow acne return t;