Navigating mental ray in Maya: ideas and experience

Since the integration of mental ray in Maya may obscure modern workflows, many of the posts here explain how to make the correct choices. But typically we assume some prior knowledge of Maya and mental ray.

We will begin a series soon on how to make modern choices and avoid pitfalls in the UI (like the default absence of shadows, no passes with materials unless using the *_passes materials, etc).

If you have experience where you have had difficulty tracking down a problem only to discover it was a checkbox or some other snafu, leave that here in the comments with a short description. We can use this information to make new users more efficient and help refresh the rest of us too. We will try and include this in sections explaining basic scene setup. Our cheat sheet for quickly rendering.

If you are a developer, it might be helpful for you to see where some defaults could be changed and alter the corresponding .mel in your installation to make a new default.

Please keep the comment factual and tidy. We reserve the right to edit it to the essence of the problem. 😉

For example:

My passes kept rendering black using the mia_material_x. I discovered I should upgrade them to the mia_material_x_passes shader.

About David

I am a VFX artist that specializes in Lighting and Rendering. I spend a fair amount of my time supplying clients with artistic solutions as well as technology solutions. With a background in fine art and technical animation training, I strive to bridge the divide between the artist and technologist.

Posted on July 29, 2012, in maya, Optimization and tagged , , , , . Bookmark the permalink. 10 Comments.

  1. Like you mentioned the default absence of shadows, go the step further and detail the steps to create mental ray area light/portal light/mia_photometric_light/ the new user env and rect lights.

  2. What immediately comes to mind are those three, will think of some more: Proper displacement setup (displacement bounds hidden somewhere in the render globals, a variety of different mental ray displacement approximation methods – which one is preferred and why), motion blur shutter angle hidden under “special effects” parameters in the camera options, volume setups of any kind (auto volume is off by default, shadow method)

  3. Joseph Briggs

    Hi,
    Ei Chuckie, what do you mean by the new user env and rec lights?
    I had that issue of render passes rendering black, I spent 2days trying to figure that out.

    Fluid containers along with a directional light to create god rays will not work if there are Portal lights activated. It will have to be rendered seperately and comped back in.

  4. I don’t know if this was ever fixed, but default filter settings on procedurals are wayyyy to high when they need to be reflected or refracted, fix is to reduce filter to something smaller, like .001. See this thread for an example: http://forums.cgsociety.org/showthread.php?f=87&t=971076

  5. Hi David, great blog! Do you have ever tried AO with bsdf_arch_comp ? I haven’t found a way to make it works…I set up mia_material_x_passes and a bsdf_arch_comp with same settings and AO doesn’t works! Hope it could be a simple option-check problem…..

    • You would need to do a separate AO pass.

      The BSDF comp material only retains those controls for the translation. AO isn’t typically used in a BSDF material description. Do a search on the ARC mental ray forum and you’ll see a couple threads covering the materials. This should clear a few things up since that material only respects a few specific controls. 🙂

  6. Great idea! There is so much topics to cover.

    I think this should be explained “by step”. Ex: “you want to create a texture to you material? Here is how you should do and which parameters you should activate”.

    A “node you should never even touch” list could be great!

    So, my suggestions:

    “For every light, decay quadratic by default with 100 in intensity”

    “For mia_x_passes shader, max trace depth to 0 by default and let global aliasing to the rest”.

    “For mia_x_passes shader, reflectivity at 1, BRDF in Fresnel and use the IOR”.

    “In lights: Suppress all Maya shader checkbox ticked by default + shadows activated”

    I suppose I forget a lot of them…

  7. For motion blur (or motion vector output), proper use of frame offset and “force motion vector calculation” option would be a good workflow tutorial. I find a lot of people just getting into multipass rendering struggling with this.

    • You can find a simplified frame offset in the new UI on Google Code. It is simplified to locations during the shutter interval/frame: beginning, middle, end.

      This is part of us looking at the feedback here and implementing a change directly in the UI. Also, with raytracing as the primary renderer now, camera vectors are handled differently. There is a string option found in the release notes. Typically for Scanline and Rasterizer, an inverse transform is applied to the scene (everything moves) this doesn’t happen with raytracing primary rays. This also improves performance.

  1. Pingback: Maya 2014 “Unfold” Event | elemental ray

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