Advanced Shadowing Options

Real shadows are rarely razor sharp. Only very compact light sources cast extremely sharp shadows, and our lives are filled with lights that have enough size that their shadows are distinctly fuzzy.

In LightWave, these "soft shadows" can be approximated by using a shadow map, but this is just a blurred transition. True area light shadows have a complex behavior since the shadow sharpness depends on the size of the light, the distance of the light, and the distance of the shadow casting object.

The proper behavior of area light shadows is actually a difficult one to render, since it deals with the partial occlusion of light sources. Gaffer is able to compute this occlusion, and therefore give shadows that behave properly. This area shadowing is an option, and normal raytraced or shadow mapped shadows can always be used instead.

Unlike shadow maps, Gaffer's area light shadows can be used with all three light types: point, spot, and distant.

As a result of the complexity of the effect, area lights are slower than both raytraced and shadow mapped lights. We'll post timing benchmarks here soon after we finish our last speed optimizations.

The visual effect of proper area light shadows can be significant. In the images to the left, you can see the effect of different shadow types. On the top left, the stark shadows from LightWave's default raytracing are crisp but unrealistic. The center image shows the use of shadow maps. LightWave's "fuzziness" option simply blurs the shadows, which gives them a much softer feel. Note how the shadows still suffer from severe problems, especially at the base of the post. Also, the shadows are evenly blurred everywhere, which looks very strange. Gaffer's area light shadows are shown on the bottom. Note the realistic behavior, especially visible in the post's shadow. The shadow is tight near the base but much more diffused further away; exactly how real shadows behave.

The question to ask yourself when you view these images is simple: Which is most realistic?