View Full Version : Mental Ray cast shadows & Ramp shaders

11 November 2005, 08:54 PM
As stated in a previous post, I've figured out how to cast shadows using the Maya Software renderer. Now my conundrum is that I actually need to render using Mental Ray's contour options for a toon style video.

Snag is with my cast shadows being projecting onto ramp shaders. The shadows come out very jagged (no gradual fade from full shadow to no shadow).

Which as you can see is not a problem in the Maya Software render after you increase the DMap Filter Size:

I'm using Maya 4.5 that came with Mental Ray 1.5. Anyone know what comparable setting I need to change to get soft shadows?

11 November 2005, 09:30 PM
Gary, that looks to me like a dmap resolution or dmap focus problem. mental ray is using different settings than Maya is to calculate the area covered by the depth map or the resolution. If you pick the shadow casting light, look in the attribute editor for the mental ray section. In there, hit the Shadow Map button and you should see an improvement in the render right away. Next, you can increase the dmap size to 512 or 1024 to get better resolution.
You mentioned needing a soft shadow - if this is the case, you'll need to turn up the softness and samples in the same mental ray section of the light. Samples of 10 and softness of .025 are a good starting point. If it looks grainy, increase the samples.
Last thing to know when you're using shadow maps is that some surfaces should have shadow casting turned off in the render stats section of the shape node. Walls, floor, moulding and carpet for example, in your scene. This reduces render time, removes artifacts and improves the quality of your other shadows.

11 November 2005, 09:55 PM
I was hoping it would be something simple like that.
So I popped back into my scene and hit those settings. When that didn't work I tried hitting the "Take Settings From Maya" button. (As seen here)

Still only got this as a result:

The shadows are still buggered.

11 November 2005, 01:57 PM
I'm thinking we're on the right track. Is there an additional setting required in Mental Rays Render Globals? Oh! And thanks for the tip to turn off shadow casting on the walls and such. :cool: Got that coved.

11 November 2005, 02:47 PM
Well I continued to tamper with the Mental Ray shadow settings and found something that could be deemed acceptable. The struggle with this was the combination of a ramp shader with no gradation and a cast shadow.

Here is the settings that I found my happy medium:

The increased softness was the balancing act. Any lower a setting and the jagged edge becomes more pronounced. Any higher and you get a scuzzy dither pattern as the ramp shader tries to make up its mind what to do.

Here's the result:

The window frame is far from perfect but some concessions need to be made.
Thanks again for your tip John. It was just what I needed.

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