MIP Indices
Actually, you have a choice of ways to translate this gradient value into a MIP level.
This also brings up one of the shortcomings of MIP mapping. MIP mapping assumes that
both the u and v components of the texture index are undergoing a uniform
scaling, while in fact the terms du/dt and dv/dt are relatively independent. Thus,
we must make some sort of compromise. Two of the most common approaches are given below:
The differences between these level selection methods is illustrated by the accompanying figure.
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