programming hints
OpenGL performance hints
Therefore, if the modelview matrix is M, the transformed plane equation is:
the rescaled normal is
and the fully transformed normal is
If rescaling is disabled, f is 1, otherwise f is computed as follows:
Let mij denote the matrix element in row i and column j of
Alternatively, an implementation may chose to normalize the normal instead of rescaling the normal. Then
If normalization is disabled, then the square root in equation 2.1 is replaced with 1; otherwise, it is calculated as dictated by the OpenGL Spec. If both normalize and rescale are enabled, HP’s implementation skips the rescale and does only the normalize.
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