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yeisnier

Culling Ligthing Influence Volume?

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Suppose there is a point light that influence all objects closer than r. To know if some object is lit by the light is easy just checking the distance to the point light. However, what about specular term. Take for instance that you are standing on a road and looking at a building that is far away, one of the floors of the buildings is iluminated with a point light that has an influence area that just iluminate part of the building. As the viewer is far from the building, the road near him is not influenced by the light and by so doesn't account for the lighting. However, if the road is wet, then the specular term will be shown on it so it takes specular lighting from that light even when it is not in the light radius. That is also seing commonly on the cars moving and making a light line in the street. So my questions is: If the lighting equation is : L = Ambient + Atten*Diffuse + Specular discarding the light influence on an object only because the Attenuation is 0 should not be correct because the specular term could influence it. Is there a way around it? Most of the implementations I have seen also multiply the Specular term by the attenuation and solve the problem, However that may not be realistic and may need a lot more of work for the artist to tweak values until the results seems real, because the specular term will get soften at the same range were the diffuse is. Is there a way around that besides just multiplying both term by the attenuation. Am I missing something here?

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Both terms should be attenuated. Specular light just simulates a more directed reflection of light; the amount of light that reaches the eye is still proportional to the inverse square of distance. In your example, the road simply has low diffuse coefficients and higher specular coefficients. In any case, the inverse quadratic attenuation factor only goes to zero at infinity.

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Quote:
Take for instance that you are standing on a road and looking at a building that is far away, one of the floors of the buildings is iluminated with a point light that has an influence area that just iluminate part of the building. As the viewer is far from the building, the road near him is not influenced by the light and by so doesn't account for the lighting.

Actually,this probleem can be solved,but indirectly.
You can make fake reflections almost everywhere in screen space,like postprocess-using full screen copy for environment bump mapping,for example.
I say just "reflections",because in case of yet road realy thin water film works:)


[Edited by - Krokhin on June 13, 2008 12:52:56 PM]

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