OpenGL 4 Shading Language Cookbook - Third Edition

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In this recipe, we used a linear relationship between the amount of fog color and the distance from the eye. Another choice would be to use an exponential relationship. For example, the following equation could be used:

In the above equation, d represents the density of the fog. Larger values would create thicker fog. We could also square the exponent to create a slightly different relationship (a faster increase in the fog with distance).