Simulating Diffuse Reflections

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Simulating Diffuse Reflections

Creating diffuse light that's reflecting to other surfaces in the scene is easily accomplished by using photon mapping. Remember, in the photon-tracing process, you traced the diffused energy being reflected to other surfaces in the scene. See Figure 14.5 for an example.

Figure 14.5. An example of diffuse interaction,indi- rect illumination ,and diffuse reflection.They are simulat ed in a box with one face missing using photon mapping.

graphic/14fig05.gif


This process is the same as in radiosity because the same color bleeding effects are simulated. For example, if a white photon reflects a red wall, the reflected photon is red. See Figure 14.6 for an example.

Figure 14.6. An example of diffuse interaction,indi- rect illumination,and diffuse reflection.They are simulat ed with two spheres next to a polygon.

graphic/14fig06.gif


The problem with using too few photons in diffuse reflection for color-bleeding effects is that it causes blotchy and discolored results. To remedy this problem, a large number of photons are to be used to blend the discoloration. A value of at least 10,000+ photons per object should be used to render diffuse reflected energy. Figure 14.7 shows the difference between 1,000 photons and 10,000 photons per object.

Figure 14.7. Diffuse reflection comparison.

graphic/14fig07.gif


NOTE

NOTE

It isn't a good idea to simulate specular (mirror) reflections in pho- ton mapping.The photon map can grow tremendously in size due to the large number of photons required to reflect light on a mir- ror's surface.

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Focus On Photon Mapping
Focus On Photon Mapping (Premier Press Game Development)
ISBN: 1592000088
EAN: 2147483647
Year: 2005
Pages: 128
Authors: Marlon John

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