Rendering a CG Scene - An Introduction to Computer Graphics for Artists - page 217

Fig. 12.3 A path traced render is physically accurate but time-consuming to produce. This render
took 50 min (Model courtesy of Robert Joosten)
tracing is more accurate (Fig. 12.3 ). The difference is that path tracing takes the
direction of refl ected rays into account but radiosity renderers do not. This causes
renders to run faster by limiting the number of calculations but the result is less
accurate than the scattering approach taken by path tracing (Pharr and Hanrahan
2000 ). Path tracing creates its own bounce light by calculating photon/object bounce
interactions until it is instructed to stop.
A popular method of lighting a scene uses a radiosity calculation to produce
light maps , which are applied to scene objects that are then rendered in real time
with a rasterizer. With this type of solution, after the lighting is calculated for the
fi rst frame, subsequent frame render times are very fast because the light maps
are used instead of new calculations. This solution does not work for scenes that
are lit with animated lights or animated objects that are meant to interact with
lighting, but has the advantage of introducing radiosity lighting into real time
rasterized renderers.