Modifying surface geometry

Abstract

So far, our shaders have only been calculating color values—the type of the result argument has been a pointer to miColor. Many shaders depend upon the shape of a surface to calculate the way in which light determines the resulting color value. By modifying the surface geometry in a shader, we can affect the calculation of that color. In a displacement shader, the result is a miScalar that defines how far along the surface normal the current point should be moved. Displacement shaders can provide geometric detail at a scale that would be very difficult to model directly.