I can't get a soft shadow with Mental Ray

[jeremybirn]

For a soft shadow from an area light, use a raytraced shadow, not a shadow map.

[Waple]

Thanks, jeremybirn!

I used Ray Traced Shadows and it is the softer shadow.

http://www.allizdog.com/miscpics/sharpshadow-fixed.jpg

But now, what I don't understand is, why didn't the Mental Ray Shadow Map work? And when would I ever use the Mental Ray Shadow Map if it looks bad?

[Anteru]

Area light sources can't work with shadow maps (except you make some tricks like PRMan). Shadow maps are for point like light sources (lightsources which emit all the light from a single point), and they are often much faster than ray-tracing. This is the main advantage, besides that they can be reused over many frames. And you can blur them uniformly nearly for free. Try to increase the samples & blur values to see what I mean.

Area lights on the other hand emit light from a surface (area), for each point on the surface a shadow ray (or more) is cast, so you get nice soft shadows, getting softer with the distance. If you would do the same with shadow depth maps, you would need to create a shadow map for every point sampled on the area light, which would be probably more expensive than ray-tracing.

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