Maya Station

Cannot open renderer description file "-mrRenderer.xml"

It's not very frequent that this terminal rendering error comes into the support or happens at all but it does happen and it will leave a few people scratching there heads.

Well, no need to worry at all.  This error is very minor and it will show up because a user has somehow overlooked at what command they are sending.  It really only takes one character to be out of place.

Below is the example we usually see.

Render -r -mr file.ma

If you look carefully,  there is a extra hyphen being used.  To fix this just remove the hyphen just before "mr".  The "-r" is the only valid flag in the above example and the render will fail because what follows is not a valid string to go with the flag.

So the correct command would be.

Render -r mr file.ma

small user error but does get missed by some folks.

Custom Color Pass Use Transparency new Feature

In the new Custom Color Pass we can use Transparency new Feature to be added in the render pass
This feature works nicely when the Shader is plugged into color. but what if you want a different color than original one.

The problem is that the writeToColorBuffer shader expects its color input to be pre-multiplied (effect of transparency already applied), the workaround is to use a multiply node to multiply the custom color by the outMatteOpacity of the main shader. 

   

The “use Transparency” option on the render pass does not actually apply the transparency to the surface color, it just determines whether objects behind the surface are visible in the case where the surface is transparent.

 

Thanks to Justin Novosad for his feedback

 

Mental ray texture bake and multithreading

This is repeated question, regarding can mental ray utilize multithreading while texture baking.
The answer is if you bake one texture map then mental ray will use only one CPU. 
However if you are using multiple maps then mental ray can utilize the additional CPU's automatically.

Frame buffer name tokens

In order to take advantage of this option, you need to have the following
Some render passes
File format set to Open EXR

Now you can enable the Automatic to custom

Light emission from IBL node increase render time in Maya 2011

Compared to previous versions of Maya the function of using Light Emission from the IBL node will dramatically increase render time.
This matter has been logged as BUG and currently under investigation by the development team.
As a workaround you can use under the "Light Emission" tab of the IBL shape, keep the "Quality U" and "Quality V" settings no higher than 7.  This is because the bug kicks in only when there is more than 56 IBL samples.

If this produces too poor quality results (grainy images), you can compensate by boosting the Sample Level under Render Settings->Quality->Anti-Aliasing Quality->Raytrace/Scanline Quality.

Workaround 2

1. select the miDefaultOptions node. 
2. In the attribute editor, open the "String Options" section.
3. Hit the "Add New Item" button.
4. Scroll to the bottom of the String Options section to find the new added
blank item.
5. Fill in the new item as follows:
 - Name: environment lighting mode
 - Value: light
 - Type: string
6. When doing preview renders in the render view, to get "smooth" results
without too many samples, set the value to "approximate" instead of "light"

Thanks to Justin Novosad for his feedback

Allocate On Heap

Maya 2011 has this new feature that can help with memory related issues.
It is off by default, but you can enable it under options tab > performance
It will allow the shading engine to store temporary data on the heap (dynamically allocated memory).

From the Documentation :
 When raytracing through transparent materials, the shading engine stores temporary data on the rendering thread's memory stack. Occasionally, a rendering thread may run out of space on the stack, causing Maya to stop unexpectedly due to a stack overflow. To workaround this, select this option so that the shading engine stores temporary data on the heap instead of on the memory stack. Selecting this option causes mental ray for Maya to render slower, but it may prevent Maya from stopping unexpectedly due to a stack overflow when using a large number of render passes in a scene with many layers of transparent objects.

Maya 2011 imf_disp is not showing the chosen pass.

If you would to render within Maya and EXR file that has imbedded passes in it.
the render view will display the master beauty render, to see the passes you would go to File > Load render pass and choose AO for example.
You would expect the display to show the AO pass, however it will show the master beauty.
The reason is the new imf_disp that is shipped with Maya 2011 will load the entire EXR file, placing the Main one at the top.

 

To view the desired pass, one should go to Layer > and choose the pass from the pull down menu.

Render passes whitepaper

Render Pass Concepts and Techniques

This white paper explains how to use the Maya render pass framework. The covered topics include: rendering pipeline efficiency, configuring and customizing render passes, and how to composite render passes. The examples show how to leverage render passes to achieve efficient compositing workflows for common rendering, lighting and look tuning tasks.

Big thanks to Justin Novosad for his hard work on this white paper.

http://usa.autodesk.com/adsk/servlet/pc/index?siteID=123112&id=13583699

mib_amb_occlusion texture on Mac OSX

Just a quick heads-up about the mib_amb_occlusion texture. Render the texture from the Maya 2011 Terminal on the Mac and you will get an unexpected result...In this example, I've connected the output of the mib_amb_occlusion texture to the Color attribute of a Maya Surface Shader (AO is disabled in the Render Settings).

This is because the value of the texture's Spread attribute is not getting correctly exported. By default the attribute is set to 0.8, but rendering from the Maya 2011 Terminal sets the value to 0.0.

You can workaround this by keying the mib_amb_occlusion Spread attribute, to force the required value to export.

Owen

Maya, mental ray standalone and iray

Outlined here is a (simplified) approach to using iray with Maya - if you have mental ray standalone 2011 licenses:

1. In Maya use 'export all' to create a .mi file,
2. Render the file from the command line: ray -iray on [further options] <filename>

For more details, including setting string options to turn on iray, see this post on the mental images forum: http://forum.mentalimages.com/showthread.php?t=6584

A couple of things to look out for:

• if your images turn out black: "Maya light sources with high intensity values", depending on the scene size that may mean very high intensity values (like 1000000 or more),
• if the quality is too low you may need to increase 'progressive max time' either in the scene/.mi file or by using the -progressive_max_time xxx option on the command line,
• if you need more samples increase 'progressive max samples' or use the -progressive_max_samples xxx option to override the value set in the file.

To compare the speed on the graphics card vs the speed on the cpu you can use the -iray option: -iray on uses the graphics card, -iray cpu uses the cpu.

If you set verbosity to 4 (add -v 4 on the command line) you can check which CUDA devices are being used:

• With -iray on you'll see something like:
  
  IRAY 0.2  info : found 1 CUDA devices
  IRAY 0.2  info : defaulting to use all CUDA devices
  
  
• With -iray cpu you'll see something like:
  
  IRAY 0.2  info : found 1 CUDA devices
  IRAY 0.2  info : empty device string, using CPU backend exclusively
  
  In case you don't have any CUDA capable devices in the system you'll see:
  
  IRAY 0.2  warn : no CUDA capable devices found
  IRAY 0.2  info : using CPU backend with 2 threads 

Thanks to Nicolas Holst for this post.