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.
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.
You can use use
color_correct with alpha_is_luminance enabled, like this:
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
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.
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
For example, if an object is visible to the camera (primary visibility), and to transmission (both diffuse and specular), then that’s
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 type Decimal Value Camera (Primary Visibility) 1 Shadow (Casts Shadows) 2 Diffuse transmission 4 Specular transmission 8 Volume 16 Diffuse reflection 32 Specular reflection 64 SSS (subsurface) 128
There’s two denoisers. Here’s when to use them:
OptiX Denoiser for fast (GPU-powered), slightly-lower quality denoising of IPR Use the
Arnold Denoiser (aka noice) for high-quality denoising of final frames and animation sequences
For more info, check the
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
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:
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.
You can use kick to render with debug shading. Here’s the flags to use:
-is to ignore the shaders assigned to the shapes
When you ignore shaders, a default utility shader is used to render the scene.
-sm sets the shade mode ( ndoteye lambert flat ambocc plastic metal)
-cm sets the color mode (color ng ns n bary uv u v dpdu dpdv p prims uniformid wire polywire obj edgelength floatgrid reflectline bad_uvs nlights id bumpdiff pixelerror)
Here’s some examples that show how to kick with different types of debug shading (I’ve used the Arnold Render View debug shading modes for these examples)
Basic: disable all shaders in the scene, switching to a gray ‘ndoteye’ shader; a very fast shading mode.
kick -is -sm notdoteye
Lighting: renders the scene with a white lambert shader
kick -is -sm lambert
Occlusion: use ambient occlusion shading
kick -is -sm ambocc
Wireframe: displays geometry as a wireframe
kick -is -cm polywire
kick -is -sm ndoteye -cm polywire
Normal: visualizes the normal vector (between 0 and 1, in tangent space)
kick -is -sm flat -cm n
UV: displays the coordinates of the primary UV set (red=U, green=V)
kick -is -sm flat -cm uv
Primitive ID: displays random colors based on the per-primitive (triangle, curve) index
kick -is -sm flat -cm prims
Barycentric: displays intra-primitive parametric coordinates (barycentric for triangles, parametric length, and width for curve segments)
kick -is -sm flat -cm bary
Object: displays random colors based on the per-object ID
kick -is -sm flat -cm obj
Arnold 5.1 adds operators, which among other things, allow you to override parameters in ass files loaded by procedural nodes.
Here’s a quick example using the brand new
I exported some particles from Softimage, loaded them into Maya with an aiStandin (aka an Arnold procedural), and then used a
set_parameter operator to scale the radius by 0.5
Note that I connect my operator by setting the
Target Operator in the Render Settings.
I can chain two set_parameter operators together, to set the mode and then scale the radius:
MtoA defines a lot of
batch render flags for Arnold. For example, here’s how to set the Arnold log verbosity and enable file logging: render -s 2 -e 2 ^
-r arnold ^
-ai:lve 2 ^
-ai:ltf true ^
-ai:lfn C:/Users/blairs/Downloads/render.log ^
First, to use the Arnold batch render flags, you need to use the Maya
-r flag to specify that the renderer is arnold (otherwise, you’ll get an “Invalid flag” error).
Then you can use the Arnold batch render flags:
ai:lve sets the log verbosity level
ai:ltf enables file logging (Log To File)
ai:lfn is the log file name. I used forward slashes; I could also have used backslashes and put quotation marks around the log file name.