AdditiveSubtractiveLight.x3d using X3DOM

This example tests various color combination capabilities, and also demonstrating that filtering (negative colors) are not supported in the X3D/VRML color model. Discussion follows. There are 2 ways to combine colors: Additive (e.g. a TV screen, overlapping spotlights, or pointillist art), for example [red + green = yellow] [1 0 0 + 0 1 0 = 1 1 0]. Subtractive (e.g. mixing paints or stacking filters), for example [white background + yellow filter + cyan filter = green] [1 1 1 + 0 0 -1 + -1 0 0 = 0 1 0].