Mathematical Structures for Computer Graphics

Chapter 9Lighting

Lighting is complex. Physics explains the fundamental properties, but in a scene there are many reflections, refractions, diffractions, and absorptions taking place everywhere, and it is this complicated set of interactions that gives us the visual experience.

Of course, there are various levels of realism we can aim for in rendering a given scene. Wireframe images, where we only draw the outlines of triangles, can give a rudimentary sense of the scene, but coloring the interiors of the triangles at least with single colors can begin to flesh it out. Simple shadows and elementary shading are enough to give a three-dimensional cast to a scene, but even animated films demand much more on the realism front.

To approach the photo-realistic look, we need to add shading from various light sources, shadows overlapping each other, and the subtleties of reflections from various surface materials. The details of these interactions remain an area of research, but more and more sophisticated lighting models can ensure that brushed aluminum furniture in a scene looks decidedly different from plastic furniture. With some care, we can approximate the fundamentals of light interactions to develop lighting models that give satisfyingly good results.

9.1 Color Coordinates

Cartesian coordinates are ideal for locating pixels on the screen, but in addition to a location, pixels have a color, and unlike location, color really depends on an individual's perception. Light is electromagnetic ...