mental ray for Maya rendering limitations
This section contains information about the unsupported features, software limitations and workarounds, as well as some tips for this version of mental ray for Maya.
Rapid scanline rendering does not support the following features:
mental ray for Maya does not support the following Maya rendering features:
The following lists the software limitations and workarounds for this version of mental ray for Maya.
The quality of depth map shadows with Rapid scanline rendering is decreased compared to the quality of depth map shadows and default scanline rendering.
In the Attribute Editor (light shape node), in the mental ray > Shadow Maps section, increase the number of Samples.
Scenes that contain custom shaders for volume effects or environment shader may not render correctly with advanced filtering (quadratic, quartic, etc.) for file textures.
Use mipmap filtering, or turn off filtering.
Imported or referenced Maya 5.0 files containing mental ray shaders, with color, scalar, or texture parameters, do not correctly convert in Maya 6.x. You may notice shaders becoming disconnected.
Open the Maya 5.0 scene file in Maya Interactive, and save it. Then import or reference the file in Maya 6.x.
When using the Maya Batch Renderer on a remote machine the User Account information (i.e. username) must be consistent between the machines to ensure that User Authentication will function correctly.
IBL provides UV coordinates to the attached shading network, but Maya's environment shaders do not base their calculations on UVs. Maya environments are supported with final gather-based IBL, but photon and light emission are unsupported.
The performance impact grows with the depth of the visited shading graphs. The cycle detection is enabled by default, but you can disable it by adding a dynamic attribute nodeCycleCheck (boolean) to the render globals node. We recommend using the cycleCheck MEL command to detect the cycle in the DG graph to fix it.
Only base meshes made of quads are supported.
To convert to quads, select Subdiv Surfaces > Collapse Hierarchy > and set the number of levels to 1.
Partial creases of subdivision surfaces are not supported in this version of mental ray for Maya. They will be rendered as full creases.
Bump nodes are not directly supported by mental ray custom shaders.
For an example of how to work with bump modes with mental ray for Maya, see devkit/mentalray/docs/gettingStarted/textureShaders_bump.html.
Bump effects are still achieveable and involves setting up your network to force bump nodes to evaluate during the render.
To get bump to evaluate, you need to map your bump nodes to one of the spare attributes on your custom mental ray material shader (that is currently not mapped).
However, if you want to use all of your material's attributes, then you need to pass the texture you really want showing up for that attribute and the bump nodes via a mib_color_interpolate node (which behaves similar to Maya's ramp texture).
First, assign your texture to the Color_0 attribute of the mib_color_interpolate node and then assign a mib_passthrough_bump_map to Color_1 attribute of the mib_color_interpolate node.
Next assign the mib_color_interpolate to any of your material's attributes (example: diffuse color) and set the input value of the mib_color_interpoloate node to a low value like 0.001 which will force the bump to evaluate while allowing you to also use the other texture for diffuse color.
Depth map shadows and particles are not supported.
Use raytrace shadows.
"Optimize Non-animated Display Visibility" needs to be turned off in the Render Global Setting window when visibility is animated.
When importing scene files containing mental ray nodes, you may see warning messages such as:
// Warning: 'Draft.message' is already connected to 'mentalrayItemsList.options'. //
These warning messages, about pre-existing connections between mental ray related node, are harmless and can be safely ignored.
A warning dialog box also appears when these warnings occur. If you are importing many files and wish to avoid manually closing the warning dialog box for every file, you may want to use the "file" command with "-prompt false".
When exporting scenes containing custom shaders to .mi format, the appropriate link and include statements are not automatically written to the exported .mi file. As a result, this file will fail to render with the mental ray standalone renderer.
In the "Custom Globals" subsection of the "Custom Entities" section of the mental ray Render Globals, you can manually enter the link and include statements for the exported file. For example, if your scene used custom shaders from the standard contour and physics shader libraries, you would specify the includes as
base.mi contour.mi physics.mi
and the links as
With these custom link/include settings, the resulting .mi file will then be renderable.
If you tear off the Maya Render menu, then load the mental ray for Maya plug-in and tear off the mental ray for Maya Render menu, Maya may crash.
Close the menu before loading mental ray for Maya.
Firewall software may block command ports. When you load mental ray for Maya, your firewall prompts you if you want "to allow the Maya application to access the internet: IP 127.0.0.1 port 1333." If you select no, Maya instantly exits without a warning or error message. If you select yes, mental ray for Maya starts up as expected.
If you are using any firewall software, you will need to give permission to Maya to communicate on port 1333 in order for mental ray for Maya to work correctly.
mental ray for Maya 6.x provides reasonable default values for mental ray shaders. In previous versions, all the mental ray shader parameters defaulted to zero. The default values are specified in the shader declaration files (base.mi, contour.mi, physics.mi) using extended .mi syntax.
As a side effect, old scenes (scenes created with Maya prior to 6.x) using mental ray shaders can render differently if a parameter value is set to 0 and its default value has been changed in 6.x.
Run mentalrayShaderDefaultCompat.mel (in maya6.x/scripts/unsupported) in Maya 5.0. For example, open Maya 5.0, and type the following in the Script Editor:
mentalrayShaderDefaultCompat ("myOldScene.ma", "myOldSceneFix.mel")
then open the scene myOldScene.ma in Maya 6.x and run the generated MEL script myOldSceneFix. This reverts the mental ray shader parameter values back to the original settings.
When rendering with motion blur, sometimes parts of deforming geometry will fail to blur.
Connections from Input Color Components (advanced shading network connection) may cause errors when rendering with mental ray for Maya.
Connections from Input Color Components: If a connection is made between single components (R, G, or B) of input color attributes on two shaders or textures, then mental ray for Maya renders will abort with error messages similar to:
API 0.0 error 301040: "maya_checker" has no member "color1" API 0.0 warn 302018: type conflict: "color" is type color, "maya_checker" returns type struct
The example message was triggered by connecting the color1R attribute of one checker texture to the color1R attribute of another checker texture.
Where possible, replace the connection between individual color components by a connection between the entire color attributes. This type of connection is supported.
The Custom Text feature is intended for use only with the mental ray 3.2 standalone renderer. To correctly render a scene containing shader/object modifications made using Custom Text, the scene must first be exported to .mi format, then rendered with the standalone product.
The following file texture formats are currently unsupported by mental ray for Maya:
(TIFF,CIN,GIF) For these unsupported file formats, Maya's imgcvt image conversion tool can be used to convert the files to a supported format such as IFF or RGB. For a complete list of file texture types supported by mental ray, see the Rendering with mental ray Handbook.
(BOT) There is currently no workaround that will allow Maya BOT files to be used in conjunction with mental ray for Maya. mental ray does support its own memory-mapped map file texture format, however. Standard image files can be converted to this format using the imf_copy command:
imf_copy -p <filename>.rgb <filename>.map
See the Rendering with mental ray Handbook for a full description of memory-mapped textures in mental ray.
When painting a texture with 3D Paint, mental ray for Maya will not pick up new paint strokes automatically.
Save either the texture being painted or the entire scene before rendering with mental ray to ensure that all strokes are rendered correctly.
The fix texture warp attribute on Maya NURBS surfaces is not supported in mental ray at this time. It changes the way textures get mapped on freeform surfaces to achieve a more realistic look on highly deformed surfaces.
Triangulate the surface in Maya and use the comprehensive polygon texture mapping tools to adapt the uv mapping.
File textures that are used for bump/displacement mapping are usually connected via their outAlpha attribute. If the corresponding texture image file does not provide an alpha channel, then the bump or displacement effect may be missing when using certain image formats.
Enable the Alpha is Luminance property in the Color Balance section of the File Texture node.
When using photon mapping effects such as Caustics and Global Illumination, any object with a Layered Shader assigned to it will behave as if it were a simple grey diffuse object. All of the shader's layers will be ignored. Layered shaders do work properly for Final Gather effects, but may cause increased render times.
Wherever possible, use Layered Textures instead of Layered Shaders.
Shading network connections involving dynamic attributes on shading nodes, and connections sourced from shading node input attributes are supported by mental ray for Maya so long as the values passing through those connections are constant for each rendered frame. Thus, these connections properly support constant and animated values, but not textures. Attempting to pass a texture through an input or dynamic attribute on a shading node will result in a warning message similar to the following:
// Warning: (Mayatomr.Nodes) : Unsupported type of connection: checker1, current plug value used instead //
Where possible, connect textures directly to the desired destination, rather than passing them through one or more dynamic or input attributes.
The following is true when rendering to a format other than Maya IFF. If rendering to Maya IFF all channels RGBAZ are written to one file. When the Depth Channel option is enabled in the mental ray Render Globals, mental ray will write out a separate image file containing depth information. Z-depth is now written out in IFF format and rendered to a separate file that has "Depth" as a suffix to the image name, for example, imageDepth.#.iff.
To cast shadows into volumes you have to increase the number of volumes samples in the "Render Stats" section of the shape node ("coneShape1"). This is standard procedure for ray trace shadows. mental ray requires you to do the same thing for Dmap shadows. To eliminate Dmap shadow artifacts on the cone boundary try increasing "Samples" in the mental ray "Shadow Map" section of the light shape node.