This Converter reads and writes Alias "polyset" files used by Alias Studio, Power Animator, Designer, and AutoStudio. It adds two entries to the conversion lists:

Alias quad .qua
Alias triangle .tri

Alias does not use these filename extensions. Interchange introduces them for convenience.

Polyset files are not the same as the native "wire" files normally used by Alias.

Alias's native "wire" file format is not documented but is supported with SGI IRIX link libraries, so Interchange cannot support it on non-SGI platforms.

The SGI IRIX version of Interchange can read and write models in the native "wire" file format used in Alias Power Animator, and adds another entry to the conversion lists:

Alias wire file *.*

Geometry
Polyset files come in two varieties. Triangle polysets contain only triangles, while quad polysets can contain both triangles and four-sided polygons.

Both files can represent objects and hierarchies, although rotational centers are not present. Interchange calculates rotational centers at the average point of each object.

Material attributes
Triangle polysets contain simple color information for each point in each polygon, but Interchange only uses the color of the first point. Quad polysets do not contain any color information. Both types of file contain texture UV coordinates that are preserved. Normals are not translated.

Options dialog

The Include view objects option on this Converter controls whether extra objects with no polygons will be added to the hierarchy of Alias quad and triangle files. These objects are named Front_eye, Front_view, Front_up, etc.

Using polysets in Alias
To save polysets, or to view or change the triangular polyset options in Alias, choose Render->triangle->O to open the option box. This selects between "triangles only" and "object separators." "Triangles only" is the default. Objects will be subdivided according to the settings in Object Mod->render stats, or if Render Globals Quality Type is set to Global, according to the Render Globals Parameters section. The "object separators" option adds hierarchy info to the file.

To activate and control the density of quad-based polyset files within the Alias software, set a shell environment variable as follows:

setenv QUAD_OUTPUT 4

where '4' is any positive integer that controls how tightly NURBs will be approximated as four-sided polygons. Alias will now save quad polyset files instead of triangle polyset files.

Smaller numbers create fewer polygons in the resulting polyset file. Note that in some areas of some models, such as trim curves, Alias will save triangles instead of quads.

For more information about using Alias polyset files, see the Alias Menu manual.

Alias "wire" files
The SGI IRIX version of Interchange also includes a Converter for Alias "wire" native files. This Converter has additional settings on its Options dialog to control the density of polygons that are used to approximate any patch surface geometry in a "wire" file.

Interchange translates all patches to polygons, similar to the controls available in the "save polygons" command in Alias.

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