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light information stored with point
Wednesday, 28 August 2002 Wed, 28 Aug '02
Hi Dayne The dot product of the light direction vector and the vector from the light too the point could be used. This is equivalent to the cosine of the angle between them. So, if you have a cone angle of 30 degrees, where the dot product was equal to cos(30) this point would be on the edge of your cone - so if you have a cone delta of 10 you could mix down from 1 to 0 between cos(30) and cos(40). or if VL is your light viewing direction and L is direction of you point. I think: luminance = 1-(dot( VL, L)-cos(coneangle))/(cos(conedelta+coneangle)-cos(coneangle)) If you want the attenuation as well you could time all this by length(VL)/attenuation. Ta Dan P.s. Don't let Ray show you his party pictures.
I am currently trying to figure out a way to determine if a point in a particle system is lit by a cone light, and store the intensity of this illumination (to allow for fadeoff in the light) with the particle/point as an attribute This value could then be used as a modifier to a shader, etc. Any thoughts on this good people? Thanks, Dayne. Jim Hensons Creature Shop London, UK.