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C..2.2 Spotlight Effect

The spotlight effect evaluates to one of three possible values, depending on whether the light is actually a spotlight and whether the vertex lies inside or outside the cone of illumination produced by the spotlight:

To determine whether a particular vertex lies within the cone of illumination, OpenGL evaluates $(\max \{\hat{v} \cdot \hat{d}, 0\})$ where $\hat{v}$ and $\hat{d}$ are as defined above. If this value is less than the cosine of the spotlight's cutoff angle (GL_ SPOT_CUTOFF), then the vertex lies outside the cone; otherwise, it's inside the cone.


next up previous contents
Next: C..2.3 Ambient Term Up: C..2 Lighting Equations Previous: C..2.1 Attenuation Factor   Contents
2001-01-10