# Determining the total illumination of a polygon

Is it possible to determine the total illumination of a particular polygon with the given light sources?

I truly acknowledge that Mathematica is not supposed to do this modeling, but it is what is at fingertips for the time being and, according to the Documentation Center, Mathematica somehow does it when rendering a 3D object:

"Directional lighting" simulates a uniform field of light pointing in the given direction. The Wolfram Language adds together the light from all of these sources in determining the total illumination of a particular polygon.

The only thing I want is to take out that brightness number from processing of graphics and now I wonder does anybody know how to accomplish that?

• What is the definition for "total illumination" and "brightness number" of a surface? Or do you want to compute the illumination of each point on the polygon separately? Aug 15, 2014 at 17:38
• @Pickett In Matematica, as I see, all points on some polygon have the same brightness. Try PolyhedronData["Tetrahedron"] as an example. Aug 15, 2014 at 18:15
• You are right, thanks for clarifying. Aug 15, 2014 at 18:34
• The rendering happens when the front end displays the graphics, so I don't think there is any way to obtain the illumination from the kernel. You could Rasterize the graphics and read a pixel value from the result but this will get tricky if there is more than one polygon. Aug 15, 2014 at 21:52