Real-Time Rendering, Third Edition, 3rd Edition

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206 7. Advanced Shading

Figure 7.3. A cone with a solid angle of one steradian removed from a cutaway view of a

sphere. The shape itself is irrelevant to the measurement; the coverage on the sphere’s

surface is the key.

In the last few paragraphs, we assumed that the light source could be

treated as a point. Light sources that have been approximated in this way

are called point lights. Just as directional lights are a useful abstraction

for lights that are far away compared to the size of the scene, point lights

are a useful abstraction for light sources that are far away compared to

the size of the light source. Intensity is useful for measuring ...