Maya to glTF exporter

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News

• Version 1.1.1 released for Windows!

• Support for Maya 2017-2020

• Added -ext option (-externalTextures) to keep textures outside of glb file

• Cameras can be exported, either by selecting them, or by passing one or more by name with the -cam <name> flag

• Skin weights are normalized to 1 now

• Export node order is now deterministic

• Fixed wrong exported frame count

• Added donet core tool to merge multiple GLTF files into one

  • This allows exporting one animation per Maya file

• Added scripts to generate animated GIF and VP9s

• Exports small animation metadata JSON file.

See the releases tab.

Installation

• Supports Maya 2017-2020, Windows 10 x64, macOS High Sierra+ and Linux

• Windows 10 x64

  • install the Microsoft Visual C++ redistributables.
    • on many systems this is already installed, so you might want to skip this step.
  • download the desired release
  • extract the downloaded zip file to any location (e.g. your desktop)
  • open the created maya2glTF folder
  • double click on the deploy batch file
    • This will copy the plug-in and scripts to your Documents folder
  • re-launch Maya

• macOS High Sierra and Linux

  • must currently be build from source, see below

Usage

• load a scene
• in the Maya script window, type maya2glTF_UI to launch the UI.
  • You might want to select the maya2glTF_UI script text and drag it using the middle-mouse-button to the Custom shelf, or even better, make a glTF shelf...
• select the meshes and cameras you want export
  • or click the select all polygon meshes button
• select the desired animation clips source using the dropdown box
  • TRAX animation clips are also supported.
    • only enabled clips on the first track are exported.
    • if you have multiple characters, select the desired one.
• hit the export selected meshes button.
  • currently the user interface is not automatically updated when you change or load a scene; just re-run the maya2glTF_UI script or hit the refresh user interface button.
• good luck! ;-)

Contributions

• let me know if this doesn't work for you
  • ideally make an issue, providing the OS, Maya and plug-in version, and a test-scene.
• if it does work, please give maya2glTF a ⭐️ on GitHUB, and spread the word 😎

Shading

• I assume you already used something like Substance Painter to create glTF-PBR textures
• select the polygons you want to shade
• click the assign PBR shader to selection button
• the first time, you need to select our PBR OpenGL shader at:
  • Documents\maya\maya2glTF\PBR\shaders\glTF_PBR.ogsfx
• next, select all the PBR textures you want to apply in one go:
  • for example, for the damaged helmet model, multi-select the following textures:
    • Default_normal.jpg
    • Default_albedo.jpg
    • Default_AO.jpg
    • Default_emissive.jpg
    • Default_metalRoughness.jpg
• now the PBR shader and all textures should be applied to your selection
• by default we use the following keyword-in-filename convention to detect the kind of texture:
  • basecolor or albedo => base color texture
  • metal or _orm => metallic texture
  • rough or _orm => roughness texture
  • occl or _orm or _ao => occlusion texture
  • normal => tangent space normal texture
    • see also the -mts flag for MikkTSpace information if your models come from Blender
  • emissive => emissive texture
  • diffuse_env => Image-based-lighting (IBL) prefiltered diffuse environment map (PMREM)
  • specular_env => Image-based-lightning (IBL) prefiltered specular environment map (PMREM)
  • brdf => Bidirectional reflectance distribution function lookup table texture
  • you can customize these conventions, see maya2glTF_assignPbrShader.mel
• all textures are optional
• set the technique to transparent if desired
• see the glTF PBR page page for more info.
• the metallic and roughness textures are always merged into a single texture when exporting.
  • If you provide JPEGs, we use Maya's JPEG encoder to generate this texture. However, the default Maya JPEG encoding settings are very low quality.
    • The following MEL snippet sets the JPEG encoder quality:

      putenv "AW_JPEG_Q_FACTOR" "92";
      

    • The following MEL code enables maximum possible JPEG quality:

      putenv "AW_JPEG_Q_FACTOR" "100";
      putenv "AW_JPEG_SUB_SAMPLING" "1x1,1x1,1x1";
      

Rationale

At IIM, we are specialized in creating realtime interactive 3D animation, for web, education, events and broadcast television, since 1992. We have developed our own multi-machine real-time 3D puppeteering software called AnimationNow, and we are about to upgrade this to make use of up-to-date rendering techniques.

If something goes wrong in our production pipeline, it usually is exporting our complex rigged Maya characters. In the past, we contributed both donations and patches to the open source OGRE exporter, but now we want to dig deep into the Maya API ourselves, so we can help out our artists if something goes wrong during the export.

glTF 2.0 seems to contain most of the features we need, and is extensible. IMHO glTF must become the defacto standard for animated 3D content. At IIM, we plan to use glTF for all our 3D assets.

Limitations

Maya interally uses a dataflow architecture (called the dependency graph). This means that power-users can connect the dependency nodes in the graph in any way they like. Unfortunately this awesome flexibility also makes it insanely difficult to develop an exporter that always works ;-)

Plugin Command Arguments

_ -outputFolder (-of) STRING _(required)* * the output folder

• -scaleFactor (-sf) FLOAT (optional)

  • scale factor to apply to the vertices

• -copyright (-cpr) STRING (optional)

  • copyright text to be embedded in the GLTF file

• -selectedNodesOnly (-sno) (optional)

  • only exports the directly selected nodes
  • by default all descendants of the selected nodes are exported too

• -sceneName (-sn) STRING (optional)

  • the name of the glTF filename
  • default is Maya scene name

• -binary (-glb) (optional)

  • exports a single glb asset file
  • default is a JSON glTF and binary bin file containing the buffers

• -externalTextures (-ext) (optional)

  • doesn't embed textures in the glb files.
  • only valid when exporting a -glb

• -camera (-cam) STRING (optional, multiple)

  • exports camera given by name.

• -initialValuesTime (-ivt) TIME (optional)

  • the time where the initial/default values can be found
  • by default frame 0 is used
  • this frame should match the skin bind pose
  • all nodes and meshes get their default transforms and weights from this time

• -animationClipName (-acn) STRING (optional, multiple)

  • the name of the animation clip

• -animationClipStartTime (-ast) TIME (optional, multiple)

  • the start time of the animation clip
  • required when exporting animation clips

• -animationClipEndTime (-aet) TIME (optional, multiple)

  • the end time of the animation clip
  • required when exporting animation clips

• -animationClipFrameRate (-afr) FLOAT (optional, multiple)

  • the frames-per-second of the animation clip
  • required when exporting animation clips
  • either you pass this for each clip, or once

• -detectStepAnimations (-dsa) NUMBER (optional)

  • pass -dsa 2 to detect STEP "interpolations" in the sampled animations curves.
  • enable this e.g. when binding the shape.visiblity to node.scale.x, y z, to prevent interpolation.
  • currently this is all or nothing, animation curves are not yet split into discrete and continuous parts

• -meshPrimitiveAttributes (-mpa) STRING (optional)

  • the attributes for the shapes to export, separated by a vertical bar |
  • by default all attributes are exported, e.g.
    • -mpa POSITION|NORMAL|TANGENT|TEXCOORD|COLOR|JOINTS|WEIGHTS

• -blendPrimitiveAttributes (-bpa) STRING (optional)

  • the attributes for the blend-shapes to export, separated by a vertical bar |
  • by default all GLTF supported attributes are exported, e.g.
    • -mpa POSITION|NORMAL|TANGENT

• -force32bitIndices (-i32) (optional)

  • forces 32-bit indices to be written to the GLTF buffers
  • by default 16-bit indices are used whenever possible

• -disableNameAssignment (-dnn) (optional)

  • do not assign Maya node names to GLTF nodes
  • by default names are copied

• -mikkelsenTangentSpace (-mts) (optional)

  • use the 'MikkTSpace' algoritm for computing the tangents instead of those from Maya
  • by default the Maya tangents are exported
    • if you imported meshes from Blender without importing the tangents, and you just use Maya for doing animation, you should use this flag.

• -mikkelsenTangentAngularThreshold (-mta) (optional)

  • the angular threshold to be passed to the 'MikkTSpace' algoritm
    • by default 180 is passed
    • in general you should not use this flag, it is mainly for debugging

• -skipStandardMaterials (-ssm) (optional)

  • do not export standard materials (lambert, phong, etc), only GLTF PBR materials.
  • by default standard materials are converted
    • but just the color and transparency is copied for now.

• -excludeUnusedTexcoord (-eut) (optional)

  • exclude texture coordinates when the mesh primitive doesn't have textures?
    • by default texture coordinates are always exported

• -defaultMaterial (-dm) (optional)

  • always generates a glTF PBR material, even if no material is assigned to a mesh in Maya
  • by default no default materials are generated

• -colorizeMaterials (-cm) (optional)

  • for debugging, generate a unique PBR material with a different color for each material
  • by default no debug materials are generated

• -dumpMaya (-dmy) STRING (optional)

  • dumps debugging info of the Maya objects to the given filepath argument
  • use the word CONSOLE to print to the Maya output window
    • WARNING: this can take a very long time if you have complex meshes!
  • by default nothing is printed

• -dumpGLTF (-dgl) STRING (optional)

  • dumps a formatted version of the glTF asset file to the given filepath argument
  • use the word CONSOLE to print to the Maya output window
    • WARNING: this can take a very long time if you have complex meshes!
  • by default nothing is printed

• -ignoreMeshDeformers (-imd) STRING (optional, multiple)

  • blend-shape or skin-cluster deformers to be ignored
  • by default no deformers are ignored
  • use this if you have deformers that are used to generate different characters, but not for animation
  • you can also add the custom attribute Maya2glTF_ignored (short name MGi) to the deformer to ignore it.
    • to maya2glTF_UI has a button to add this attribute to the selected deformer(s)

• -skipSkinClusters (-ssc) (optional)

  • skip all skin cluster deformers, as if the mesh was not skinned
  • by default no skin clusters are skipped

• -skipBlendShapes (-sbs) (optional)

  • skip all blend-shape deformers, as if the mesh was not morphed
  • by default no blend-shape deformers are skipped

• -redrawViewport (-rvp) (optional)

  • redraw the viewport when exporting animation.
  • by default the viewport is not refreshed, since this slows down the exporter

Status

I consider this plugin to be production quality now, but use it at your own risk :)

• Supports Maya 2017-2020 (64-bit only)

  • Maya 2016 is not supported any more

• Linux support hasn't been tested a lot.

• Supports static and animated, skinned and morphed meshes

  • Currently all animation is baked per frame, no compression is done yet

• Supports multiple animation clips (node and joint transforms, blend shape weights)

  • Blend shape targets are not sparse yet

• Exports POSITION, NORMAL, COLOR, NORMAL, TANGENT, TEXCOORD, JOINTS and WEIGHTS attributes

• Supports exporting to glTF + bin, single glTF or single glb files.

• Uses a modified fork of the glTF code from the COLLADA2GLTF project

• Currently Phong, Lambert and Blinn shaders are converted to PBR, but only the color texture and transparency is taken into account (this is mainly done for testing with existing models).

• Comes with GLSL code with a friendly UI ported from the official Khronos PBR WebGL code.

  • See maya2glTF\maya\renderData\shaders\glTF_PBR.ogsfx
  • To use this hardware shader
    • make sure the GLSL shader plugin is loaded
    • use the OpenGL/Core Profile in Preferences/Display
  • You can use the maya2glTF\maya\scripts\assign_glTF_PBR_material_and_textures.mel script to assign multiple textures at once, based on filename patterns

• Supports exporting cameras

• No lights yet

  • support for the KHR_lights_punctual will be added at some point, PR welcome, see issues

Building

• Currently out-of-the-box downloads are only provided for Windows x64

  • If you want to try the exporter, but you can't build it, give me a sign

• I assume you already installed a GIT client

• Some versions of Maya require a Maya devkit

  • Seems not needed for Maya 2018+

• Clone this repository

  • Open a command prompt (aka terminal), and run

  git clone https://github.com/iimachines/Maya2glTF.git --branch master
  

Building for Windows

• Install Visual Studio 2019

  • Select at least the C++ desktop development payload
  • In the individual components tab, select:
    • the Windows 8.1 SDK
    • the Windows Universal CRT SDK
  • This document was written for Visual Studio 2019, other versions might not work.

• Install the Win64-x64 version of CMAKE

  • Make sure to add CMake to the system path

• Enter the maya2glTF folder, and run

  windows_create_vs_project -D MAYA_VERSION=2020
  

  • Change 2020 in the Maya version you want to target.
  • After a couple of seconds, a Visual Studio solution should be generated in the build folder.

• Next build the maya2glTF plugin itself

  • Launch Visual Studio 2019

  • Open the solution maya2glTF\build\maya2glTF.sln

  • Select the desired configuration target (e.g. release)

  • Build

  • If all goes well, the plugin and all scripts will be copied to your %userprofile%\Documents\maya folders

Building for MacOS

- install [XCode](https://www.apple.com/us/search/xcode) from the app-store
- install [CMake](https://cmake.org/download/)
- open a Terminal window
    - See `Finder` `Utilities` `Terminal`
- clone this repository
    - e.g. `git clone https://github.com/iimachines/Maya2glTF.git ~/Documents/Maya2glTF`
- enter the cloned directory
    - e.g. `cd ~/Documents/Maya2glTF`
- create the build script by running
    - `./osx_create_project.sh 2020`
    - Replace 2020 with the Maya version you're targetting
- enter the generated `build` folder, and `make` the plugin
    - `make`
- if all goes well, the plugin should be ready to be used.

Building for Linux

- TODO

Testing the build

• Start Maya

• Load a scene

  • NOTE to load scenes from this project, first set the Maya project to the maya2glTF\maya folder

  • to see if the plugin was built correctly, it's best to use a scene from this repository, for example maya2glTF\maya\scenes\damaged_helmet.ma

• select the meshes and cameras you want to export

  • by default all descendants are also exported, unless you add the -selectedNodesOnly (sno) flag.

• run the following MEL script

maya2glTF -outputFolder "<your output folder>"

• I use the vscode glTF viewer

  • Make sure to switch between BabylonJS, Cesium and ThreeJS, they all give different results... For our own assets, it seems ThreeJS gives the best results.

• If you want to contribute to the development, you might want to use the MEL script maya2glTF\maya\scripts\test-iteration.mel. This unloads and reloads the plugin everytime, unlocking the DLL.