Mental Ray Shadow Map issues

Quique · August 16th, 2006

Hi all,
Please see attached images for reference. I have enabled 'transparent shadows' in the mr Area Spot lights in my scene ( set to use mr Shadow Map). I like the quality of the shadows, however, some of my textures come out very different. You can see the brick on the columns seems to have almost no bump at all, and the wood texture on the low wall seems like a flat brown. I have turned off GI so as to not contribute to troubleshooting, so sorry for the dark images. I'd like any suggestions from people who use MR for interiors as I am using this as an exercise in learning MR.
Thanks!
Light spec's:
Map Size: 1024
Sample Range: 0'0"
Samples: 4
Use Bias (unchecked)
Transparent Shadows (checked)
Color (unchecked) [changed, it doesn't affect outcome]
Merge Dist: 0'0"
Samp./Pixel: 4

Quique · August 16th, 2006

Update:

I was able to get the wood texture back by increasing the Shadow Map size to 2048 on one particular light. The odd thing is, that according to this light's falloff settings, it shouldn't affect the wooden object at all.

Thiago de Andrade · August 16th, 2006

I think you should also try changing the colour temperature. And by the way, what is the type of light you're using? Maybe that's the answer.

Quique · August 16th, 2006

Thiago,

Thanks for the reply. I don't think the light color or intensity is what is affecting my material/shadow problems. The type of light I am using is the mr Area Spot light, as I mentioned in my first post. The light has a very small hotspot, and a very large falloff, to simulate the light output of a flourescent light box (with an aspect ratio of 1:2 for a rectangular shape). I am trying ray traced shadows right now for some of my lights, which gives me more accurate shadows, but takes a lot longer to render. I'm still trying to find the right balance.

Enrique

Justin Hunt · August 17th, 2006

I try to avoid shadow maps for area lights, raytrace is better. if the area samples are greater than 8 it will have a big hit on the rendertime. The transparent shadows only affect shadows on transparent objects.

JHV

Quique · August 17th, 2006

Justin,

Thanks for the reply. I also thought that the transparent shadow option only affects transparent objects, but it's hard to argue the results between the first two pics I posted. I don't know why the shadows under 'transparent shadow' look better, but they do, especially around the chairs. These renderings take about 15-20 mins. on my computer, but changing just some lights to ray tracing will make my rendering times take an hour. I will post an update if I find a suitable solution.

Enrique

Justin Hunt · August 17th, 2006

What are your area light settings? I take it you are using a MRarea spot.

JHV

August 16th, 2006	#3 (permalink)
Thiago de Andrade Senior Member Join Date: Apr 2005 Location: Brasília Age: 28 Posts: 132 Name: Thiago de Andrade	Re: Mental Ray Shadow Map issues I think you should also try changing the colour temperature. And by the way, what is the type of light you're using? Maybe that's the answer.

August 16th, 2006	#4 (permalink)
Quique Member Join Date: Nov 2002 Location: College Station, TX, USA Posts: 43 Name: Enrique Camacho	Re: Mental Ray Shadow Map issues Thiago, Thanks for the reply. I don't think the light color or intensity is what is affecting my material/shadow problems. The type of light I am using is the mr Area Spot light, as I mentioned in my first post. The light has a very small hotspot, and a very large falloff, to simulate the light output of a flourescent light box (with an aspect ratio of 1:2 for a rectangular shape). I am trying ray traced shadows right now for some of my lights, which gives me more accurate shadows, but takes a lot longer to render. I'm still trying to find the right balance. Enrique __________________ 3DS Max 2009, i7 920, 6 GB Ram, Powercolor Radeon 4850, Vista 64, No overclocking anywhere. www.enriquecamacho.com

August 17th, 2006	#5 (permalink)
Justin Hunt Veteran Member Join Date: Jan 2005 Location: Brisbane Age: 34 Posts: 1,380 Name: Justin Hunt	Re: Mental Ray Shadow Map issues I try to avoid shadow maps for area lights, raytrace is better. if the area samples are greater than 8 it will have a big hit on the rendertime. The transparent shadows only affect shadows on transparent objects. JHV

August 17th, 2006	#6 (permalink)
Quique Member Join Date: Nov 2002 Location: College Station, TX, USA Posts: 43 Name: Enrique Camacho	Re: Mental Ray Shadow Map issues Justin, Thanks for the reply. I also thought that the transparent shadow option only affects transparent objects, but it's hard to argue the results between the first two pics I posted. I don't know why the shadows under 'transparent shadow' look better, but they do, especially around the chairs. These renderings take about 15-20 mins. on my computer, but changing just some lights to ray tracing will make my rendering times take an hour. I will post an update if I find a suitable solution. Enrique __________________ 3DS Max 2009, i7 920, 6 GB Ram, Powercolor Radeon 4850, Vista 64, No overclocking anywhere. www.enriquecamacho.com

August 17th, 2006	#7 (permalink)
Justin Hunt Veteran Member Join Date: Jan 2005 Location: Brisbane Age: 34 Posts: 1,380 Name: Justin Hunt	Re: Mental Ray Shadow Map issues What are your area light settings? I take it you are using a MRarea spot. JHV

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