Softimage in Performer (pfhrc loader)

by Dave Pape (pape@evl.uic.edu>

This document describes the Softimage HRC loader that I have been developing for Performer. The loader reads a Softimage model (.hrc file), and creates a Performer scene graph for the model. It can be used to import Softimage models into Performer/CAVE applications; see my "Performer by Example" for an introduction to using Performer in the CAVE. The loader is a standard pfdb DSO library, so it can be used with regular Performer applications, such as perfly.

The source code for the loader is available for downloading or browsing. Within EVL, the compiled DSOs can be found in ~pape/lib/.

The loader has been tested with Performer 2.1, with models created by Softimage 3.0. Please report all bugs to me.

Using the loader

To use the hrc loader, you must first process your models slightly for it to be able to read them. Specifically, the hrc files must be in ASCII, rather than the default binary format, and texture map images must be in SGI format, rather than Softimage pic format. hrc files can be translated to ASCII using hrcConvert; images can be translated using soft2sgi (both of these programs are part of Softimage). You should also make sure that the texture images have dimensions which are powers of 2, or Performer may have problems with them.

The shell script ProcessHrc will automatically perform the necessary conversions, including resizing to powers of 2. It assumes that the commands hrcConvert, soft2sgi, imgsize, and izooms are in your path. (izooms is a non-standard SGI image tool; if you do not have it, a copy is here.) One important note: Softimage saves the full path for texture files in the hrc file; the ProcessHrc script strips off the path and just leaves the base file name (without the extension). To do this, it assumes that all file paths include the string "usr" (and that "usr" appears nowhere else in the hrc file); this normally works fine with EVL filesystems, but may need to be changed for other systems.

Once the hrc and texture files have been converted, they're ready to be loaded. Assuming your program uses pfdLoadFile() to load models, you just need to set the PFLD_LIBRARY_PATH environment variable to tell Performer where to find the hrc loader DSO. For example:

	setenv PFLD_LIBRARY_PATH ~pape/lib
	perfly model.hrc

Limitations

Softimage has a strange notion of how hierarchical transformations are applied, which I haven't worked out yet. Therefore, it is best to freeze the transformations in a model (via Effect->Freeze) before saving it for Performer. Note that freezing can screw up the texture mapping of some parts of your model (this is visible in Softimage, not just in Performer); if this happens, you should change the polygons which have problems to use UV texturing before doing the freeze. The change can be done via Txt_Oper->Info_UV_Coord.

The hrc loader does not support all the possible features of Softimage models; only those which can be handled by Performer and which I have had time to code. In short, it supports polygonal models, materials, and basic 2D textures. All unsupported features are ignored (i.e. they shouldn't cause it to crash).

More specifically, the types of geometry that are supported are:

polygon meshes
faces
linear patches (right now all patches are treated as linear, even if they're actually BSpline or some other type)
splines (also treated as linear - i.e. a poly-line formed from the control points)

The texturing options that are supported are:

UV, XY, XZ, YZ, SPHERICAL, and CYLINDRICAL methods
U/V repeats
U/V swapping

Support for other features will be added as the need arises, assuming they are possible in GL/Performer.

Last modified 5 February 1999.

Dave Pape, pape@evl.uic.edu