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Figure 9 shows the effect of different vector
normalization methods. So as to avoid precision problems the specular exponent
is relatively small (
).
Figure 9:
Quality of Different Normalization
Methods
|
Gouraud shading to the left is only shown for reference purposes.
Without normalization it is clearly visible, that the shape of the highlight
and intensity are not correct. With register combiner normalization the
results are astonishingly good, although that only a linear square root
approximation is used for normalization. The visible banding effects are
primary caused by the limited precision for the exponentiation of the specular
intensity. 8 bit cube map normalization works not as good as expected. One
cause is that one more bit in comparison to register combiner normalization
gets lost as the whole range
must be range compressed to
(register combiners work internally with 8+1 bits so the range is
). The best render quality is reached by using a 16 bit
normalization cube map in combination with a high precision dot product in the
texture shaders.
Gerald Schröcker
2002-03-21