by Greg Ward and Paul Heckbert
A new method for improving the accuracy of a diffuse
interreflection calculation is introduced
in a ray tracing context.
The information from a hemispherical sampling of the luminous
environment is interpreted in a new way to predict the change in
irradiance as a function of position and surface orientation.
The additional computation involved is modest and the
benefit is substantial.
An improved interpolation of irradiance resulting from
the gradient calculation produces smoother, more accurate
This result is achieved through better utilization of ray samples
rather than additional samples or alternate sampling strategies.
Thus, the technique is applicable to a variety of global illumination
algorithms that use hemicubes or Monte Carlo sampling techniques.
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