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The Hemicube in Action.
This illustration demonstrates the calculation of form factors between
a particular surface on the wall of a room and several surfaces of
objects in the room.
A standard radiosity image generation algorithm will compute the
form factors from a point on a surface to all other surfaces, by
projecting all other surfaces onto the hemicube and storing, at each
discrete area, the identifying index of the surface that is closest to the
point. When all surfaces have been projected onto the hemicube, the
discrete areas contain the indices of the surfaces which are visible to
the point. From there the form factors between the point and the
surfaces are calculated.
For greater accuracy, a large surface is broken into a set of small
surfaces before any form factor calculation is performed.