[macOS] Rendering xgen procedurals in another app


Or: how to fix the node xgen_procedural” is not installed problem.

For example, suppose you want to render XGen hair in CINEMA 4D on macOS.

  • From MtoA, export your XGen hair to an ass file.
  • Set DYLD_LIBRARY_PATH before you start your application (for example, open a Terminal, set DYLD_LIBRARY_PATH there, and start CINEMA 4D the command line)
    export DYLD_LIBRARY_PATH=/Applications/Autodesk/maya2018/plug-ins/xgen/lib:/Applications/Autodesk/maya2018/Maya.app/Contents/MacOS
  • Load the ass file into CINEMA 4D with an Arnold Procedural.
  • Set the Plugin Search Path to the MtoA procedurals folder

ShadingGroup has no surfaceShader input


If you see this warning when you render

Warning: [mtoa] [translator polymesh] ShadingGroup exampleSG has no surfaceShader input

it’s because a shadingEngine node either has nothing connected to the surfaceShader port, or (more likely) it has an unknown node plugged into surfaceShader.

For example, if you load a scene that was set up with a different renderer, and that renderer is not loaded, then you’ll get some “ShadingGroup has no surfaceShader input” warnings.

ERROR | [aov] more than one output statement was associated with single layer driver: defaultArnoldDriver@driver_png.RGBA


This error means that you are trying to render multiple AOVs into a single file, and the file format (PNG in this example) does not support that.

JPEG, PNG, and TIFF cannot have multiple AOVs in a single file. The AOVs have to be rendered in separate files.

If you get this error, check the Common tab. If you don’t see the <RenderPass> token, then you’re going to get the “more than one output statement was associated with single layer driver” error.

For JPEG, PNG, and TIFF, you need the <RenderPass> token:

Normally, MtoA will automatically add the <RenderPass> token for you. But sometimes Merge AOVs gets enabled for EXRs, and then the Image format is changed to another format, like PNG.

So just switch back to EXR and disable Merge AOVs. Then switch back to the other image format.

backdoor Arnold: setting visibility


If you want to control object visibility with operator, or the Arnold Python API, or by editing an ASS file, you need to understand Arnold’s visibility parameter.

In the UI, the object visibility options look like a bunch of separate parameters:

 

but in Arnold, all those options are stored in one visibility parameter.

For example, if an object is visible to the camera (primary visibility), and to transmission (both diffuse and specular), then that’s visibility 13.

Why 13? Because 13 = 1 + 4 + 8

  • camera rays = 1
  • diffuse transmission rays = 4
  • specular transmission rays = 8

The Arnold visibility parameter tells Arnold the rays to which the object is visible.

  • visibility 0 means the object isn’t visible to any rays
  • visibility 255 means the object is visible to all rays
  • visibility 253 means the object isn’t visible to shadow rays (so the object does not cast shadows).

Here’s the decimal values for all the different ray types.

To figure out the visibility, just add up the values for the rays you want.

Ray typeDecimal Value
Camera (Primary Visibility)1
Shadow (Casts Shadows)2
Diffuse transmission4
Specular transmission8
Volume16
Diffuse reflection32
Specular reflection64
SSS (subsurface)128

The case of the too-low OptiX version


In this case, when the user tried to render after enabling the OptiX denoiser, they got this error:

ERROR | [gpu] OptiX version 0.30.91 is lower than the minimum required version 5.0.0

This was with MtoA 3.0.1, which means Arnold 5.1.1.0

So, that means there is an incompatible version version of the OptiX library on the system, and it’s being loaded instead of the OptiX that ships with MtoA.

I probably could have just checked the PATH setting, but I used Process Monitor to absolutely sure, and I found this:

pml_furryball_optix

The problem is that another renderer added itself to the PATH. That’s a bad thing 😉

The solution? Remove that folder from PATH. Create a batch file or wrapper script to set the required environment when you start Maya to use the other software. Rather like the mtoa module file sets PATH when you start Maya.

NOTE In previous versions of MtoA, this would prevent MtoA from even loading.