PDA

View Full Version : I can't get a soft shadow with Mental Ray


Waple
07-12-2004, 06:31 PM
http://www.allizdog.com/miscpics/sharpshadow.jpg
No matter what I do, I can't get anything but a sharp, crappy shadow. This was done with 1 MR Area light with a Mental Ray Shadow Map, and Global Ill and Final Gather both turned on.

I've tried turning sampls up on the shadow map, a wider and narrower light cone, and everything else I can think of. Even when I go through the MR tutorials, I can't get a soft shadow like they are showing. I'm assuming something is turned on or off but no idea what it is.

Please help me before I drive a nail through my monitor.

jeremybirn
07-12-2004, 06:39 PM
For a soft shadow from an area light, use a raytraced shadow, not a shadow map.

Waple
07-12-2004, 06:55 PM
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
07-12-2004, 07:42 PM
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.

CGTalk Moderation
01-18-2006, 04:00 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.