Mai-Tai Attributes

Some Mai-Tai variables, such as the name of a RenderMan shader to use, can be associated with specific objects. Since these variables may be different for each object in the scene they cannot be part of the Mai-Tai globals. Instead, they are represented as additional Maya attributes. It is up to the Mai-Tai user to add these attributes when the default values are not acceptable.

Add To Selected

To add Mai-Tai attributes, first select one or more objects in Maya. The selected objects may be geometric primitives or light sources. Next, pull down the Mai-Tai menu and expand the "Add To Selected" sub-menu:

There are six different kinds of attributes. Each will be described in turn below.

Object Attributes

These attributes may be added to any geometric primitive.

Environment Map

Checking this box causes Mai-Tai to automatically create a cube face environment map and apply it to the selected object so that it will appear reflective. Creating a cube face map involves six "pre-flight" rendering passes from the point of view of the selected object. Therefore, it should be used sparingly to minimize the total number of renders. Primitives in proximity may share one environment map.

If the surface shader is left blank, objects with the Environment Map box checked will default to the RenderMan "shinymetal" surface.

Surface Shader

Enter the name of a RenderMan surface shader here and it will be applied to all selected geometric primitives. This assumes that the user has created the RenderMan shader offline, compiled it, and installed it on the shader search path. If this field is left blank, Mai-Tai will select "shinymetal" for objects with Environment Mapping turned on. Otherwise, it will default to either the Blinn, Lambert, or Phong shader as determined by the Maya shading group.

Surface Parameters

Parameters to the RenderMan surface shader may be passed here using the RIB syntax for token-value pairs. Tokens must be within quotation marks and should match the name of one of the parameters of the RenderMan shader. Each token is followed by a value contained within square brackets. The value should match the type and number of the parameter to the RenderMan shader.

Displacement Shader

Just like the surface shader above, one may specify the name of a RenderMan displacement shader here. The RenderMan shader must be created offline, compiled, and installed it on the shader search path. The default is to have no displacement.

Displacement Parameters

Pass parameters to the RenderMan displacement shader here using the RIB syntax for token-value pairs.

Polygon Attributes

These attributes may be added to polygonal primitives, instead of or in addition to the object attributes described above.

Export as Subdivision

Checking this box causes Mai-Tai to convert a Maya polygon mesh to a RenderMan subdivision surface primitive. The "interpolateboundary" tag will be set to prevent unattached edges in the polygon mesh from shrinking inward. The resulting render will often appear smoother and less faceted than rendering the polygon mesh directly.

Export as Bicubic

If the polygon mesh is a perfectly square grid of quadrilaterals, then it may be rendered as a b-spline mesh. The results are undefined when the mesh has any other topology. Unlike subdivision surfaces, the boundary of the mesh will not be interpolated. The rendered geometry will be smooth but smaller than the original by one row of quads on each side of the mesh.

Smooth Normals

Mai-Tai can automatically compute smooth normals within a polygon mesh. The normal at a vertex will be the average of the surface normals of all facets that share the vertex. All adjacent facets will then share that normal vector as well. This approach is sometimes called Phong shading. Unshared vertices such as at the corner of a mesh will simply have the surface normal of the only adjacent facet.

Light Attributes

These attributes may be only be added to light objects.

Light Shader

Enter the name of a RenderMan light shader here and it will be applied to the selected light object. This assumes that the user has created the RenderMan shader offline, compiled it, and installed it on the shader search path.

Light Parameters

Parameters to the RenderMan light shader may be passed here using the RIB syntax for token-value pairs. Tokens must be within quotation marks and should match the name of one of the parameters of the RenderMan shader. Each token is followed by a value contained within square brackets. The value should match the type and number of the parameter to the RenderMan shader.

Curve Attributes

Attach these attributes to curves, instead of or in addition to the object attributes above.

Do Export

Because curves in Maya are general for reference or animation, the default is to not export them to RenderMan for visible rendering. Add curve attributes and check the "Do Export" box in order to make curves visible.

Base and Tip Width

These specify the width in object space of the curve. The beginning of each curve is considered the base and the last part is called the tip. A curve can be made to taper by specifying a tip width narrower than the base width.

Base and Tip Rotation

By default, Mai-Tai will export curves so that the normal remains facing the camera at all times. This gives the curve a more constant looking width and is ideal for modeling tubes or hair. To make a curve twist like a ribbon, offset the base and/or tip rotation. The units are in signed degrees. For example, if the base rotation is -360 and the tip rotation is +360, the curve will twist two full times along its length.

Fur Attributes

Use these attributes to add fur to parametric primtives such as NURBS. To edit the attributes, select the object and open the Maya attribute editor. The fur attributes will be in the section labelled "Mai-Tai Fur Rendering:"

Mai-Tai Fur

Set Fur Type to "Mai-Tai Fur" and Mai-Tai will create the individual curves for the fur itself. Control the statistical characteristics of the fur under "Mai-Tai Fur Settings". The three colors will be passed to the RenderMan surface shader called "hair" that is provided with Mai-Tai.

Maya Fur

The other option is to let Maya create the curves that make up the hair and export it to Mai-Tai through temporary files. Set Fur Type to "Maya Fur Render" and select the name of the directory to hold the temporary files. There's an extra step when using Maya Fur: manually exporting the fur files. Go into Maya's Rendering module, pull down the Fur menu and select "Advanced Fur Rendering":

Check the "Fur Files" radio button and under "Put Fur File Here" enter the same directory name as in Mai-Tai Fur Rendering. If these directory names do not match, then the fur description will not be communicated from Maya to Mai-Tai.

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