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7.5. Fragment Processing 167
1. Calculate the intensity of the light at each vertex of the model; that is,
the computed colors at each vertex.
In Section 7.5.1, we derived equations to calculate the color intensity at
a point on the surface of a polygon. We use these equations to calculate
the color intensity at vertex i. The normal N used in these equations is
taken to be the average of the normals of each of the polygon surfaces
which are attached to the vertex. For example, to calculate the light
intensity at vertex i, as shown in Figure 7.12, we need to compute the
normal at vertex i. To do this, we need to average the surface normals
calcul ...