Houdini Engine for Maya
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At the moment, mesh is the only geometry that has material support. Material support is implemented through string attributes, namely maya_shading_group and shop_materialpath. Similar to a typical Houdini workflow, setting these string attributes is equivalent to assigning materials.

  • maya_shading_group - detail|primitive string

When geometry is inputted from Maya into a Houdini asset, the name of the Maya shading group that is assigned to the geometry is stored in the maya_shading_group string attribute. When this string attribute is output from an asset, the output Maya geometry will be assigned to the corresponding shading group.

The original intention of the attribute is to preserve the material assignment when the geometry is input into, and output from Houdini Engine. However, the attribute could also be used to control the material assignment of the output geometry. For example, the asset could explicitly create the maya_shading_group attribute, and set it to the name of a Maya shading group. Then when the geometry is output into Maya, if the shading group exists, the geometry will be assigned to the corresponding shading groups.

  • shop_materialpath - detail|primitive string

In a typical Houdini workflow, materials are assigned through the shop_materialpath attribute. When an asset outputs geometries that contain Houdini materials, some basic parameters of the materials are recreated in the Maya scene. Materials in Maya are created as phong. And the basic parameters ogl_diff, ogl_amb, ogl_alpha, and ogl_spec, ogl_tex1 of the Houdini material is output into the Maya material.

If your HDA has materials where file textures are being baked out for Maya, we recommend that in Maya's Display Preferences you set the MaterialLoadingMode to Immediate in order to be able to see the changes to the output textures updating.