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Next: Limitations Up: 10.6 Bump Mapping with Previous: Blending   Contents Bumps on Surfaces Facing Away From the Light

Because this algorithm doesn't take surfaces facing away from lights into account, the forward differencing calculation will produce ``lights'' on the surface even when no light is falling on the surface. Use the result of $\vec{L} \cdot \vec{N}$ to scale the shift so that the bump effect tapers off slowly as the surface becomes more oblique to the light direction. Empirically, adding a small bias (.3 in the authors' experiments) to the dot product (and clamping the result) is more visibly pleasing because the bumps appear to taper off after the surface has started facing away from the light, as would actually happen for a displaced surface.