Strange problem in Mental Ray - textures not appearing in reflections

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  04 April 2012
Strange problem in Mental Ray - textures not appearing in reflections

Okay, so I swear this problem is bespoke to me, because I've searched everywhere and haven't found any mention, let alone a solution.

Basically, textures aren't appearing in reflections or refractions - bump or normal maps.



It's frustrating, because I've tried everything - is there a plugin I've accidentally disabled? Do I need to increase sample values anywhere? Or what?

You'll also notice in the screenshot a strange dark area beneath the glass - this is the first time it's happened, so it's not my primary concern, but I was wondering if there was a solution to this too? I've used the same preset shader before, no problems, so I think it may be my light setup. A common problem? Also, why does the glass make the rest of the scene brighter when looked through?

Thank-you in advance! Hope there's a quick solution for both these issues.
 
  04 April 2012
Just a quick notice: I only get the dark error with mia_material.
 
  04 April 2012
Looks like you have more problems than just the refractions.



The shading is gone from there as well. I am assuming that is where some sort of raytraced shadow would go?
 
  04 April 2012
That's with caustics turned on and Photon emission from the area light I have to the left of the scene.
If it helps, I also have a HDRI image in the scene.

I'll try turning off photons/caustics to see if I can isolate the problem.

However, it's still the reflection/refraction problem that's the main concern. Any help here is greatly appreciated, because I really need to resolve this problem in order to continue!
 
  04 April 2012
1. Turn up your raytrace settings. Render settings -> quality -> raytracing

2. Check the Ray Depth limit on any shadow casting lights.

3. Set your Final Gather Tracing settings to match that of your raytracing settings.
 
  04 April 2012
Originally Posted by LowJacK: 1. Turn up your raytrace settings. Render settings -> quality -> raytracing

2. Check the Ray Depth limit on any shadow casting lights.

3. Set your Final Gather Tracing settings to match that of your raytracing settings.


This has proved useful in reducing the intensity of the result, but I'm a little unsure as to what the values shoudl be.

Do you have any suggestions for values? Anything to ensure I completely eradicate the adverse effects in my image? Render times are not a concern for me, so as high as possible to ensure they don't appear again!

Thank-you!

Last edited by Ubermatik : 04 April 2012 at 02:09 PM.
 
  04 April 2012
The trace depth values are different depending on the scene. For reflections 3 usually is good but it's worth testing more. As for refractions add 1 for each transparent face that is culled. For this scene you have 4 sides of the glass that are visible through each other. The shadow depth is for how many reflections/refractions shadows are visible through. You'll probably have to have this as high as your refraction depth. When in doubt either add 1 or reduce 1 to a trace depth value and see if there's any visible difference between renders.

-Dan
 
  04 April 2012
Originally Posted by kanooshka: The trace depth values are different depending on the scene. For reflections 3 usually is good but it's worth testing more. As for refractions add 1 for each transparent face that is culled. For this scene you have 4 sides of the glass that are visible through each other. The shadow depth is for how many reflections/refractions shadows are visible through. You'll probably have to have this as high as your refraction depth. When in doubt either add 1 or reduce 1 to a trace depth value and see if there's any visible difference between renders.

-Dan



This has helped enormously, Dan, thank-you so much! It's cleared out my issue with dark refractions/shadows in the glass, which is excellent. Here's an image of my progress so far - yet the main problem still persists - no reflection/refraction of textures - both normal and bump! I even toned down the cloth map to see if it had any difference, but nope. Much in the way you can set depth limits and values for raytracing, is there something I need to increase in order to see textures through the glass? Is it, in fact, the same values I edited to get a better result with the lighting/shaders?



Thanks for all your help! I can see a solution to these problems slowly emerging.
 
  04 April 2012
I'm assuming this is Maya... What's your filtering like on that tablecloth texture? Default is Quadratic. Try Mipmap, with a filter strength of 2?

Is your Primary Renderer set to "Raytracing"? Default would be Scanline. Also, are you using BSP2 or Regular BSP?

There are five bounces through your glass to your texture. A good default ray depth would be 6/6/12, which you can then tone down later once it's all working.
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  04 April 2012
I'm guessing that the texture on the tablecloth is a procedural.

Try turning off filtering entirely on the texture, and see if this fixes the problem. If it does, then start to dial in the filter settings until you get an acceptable result.
 
  04 April 2012
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