CompuServe Messages

You seem to be asking about penumbral decay of the spotlight, not attenuation over distance for spot and omni lights. Given that, are you sure you _really_ want to know? <g> Basically, spotlight decay uses a cubic spline with hermite interpolation that's shaped like an s, so that the spline is tangent to 1 and 0 (it has 0 first and second derivatives at the ends). The formula is: u*u*(3-2*u) …where u is a number which goes from 1-0 as you go from the hotspot to the falloff. (0 at the outer range and 1 at the inner range) That's for circular spotlights. The rectangular ones are a hybrid variant that's way too complex to explain in an email. (does anyone else do rectangular lights?) – G