
	SLA2gf

	Usage: SLA2gf infile outfile


	Example

		SLA2gf robot.sla robot.gl

	SLA stands for "StereoLithography Apparatus", and is a
	very popular machine for 'rapid prototyping'.  This
	machine can produce (overnight) plastic 3D models of
	parts directly from CAD databases.  This allows designers
	to test assembly, verify design, and (sometimes) use
	the plastic parts as prototypes.

	Several large CAD/CAM software systems produce data files
	suitable for the SLA machine. (We use both PRO/Engineer
	and Unigraphics-II.)  The SLA files can be produced quickly,
	in either an ASCII file or a binary (smaller) format.  The
	SLA2gf filter can (currently) only read the ASCII format
	SLA files.

	There are only a few, known software packages that can discplay
	an SLA file on a computer workstation.  One comes with the
	the SLA machine and software support for that machine when
	you buy one.  The others that I know of all rely on the
	Silicon Graphics GL graphics library, and run only on computers
	which support that library.  This SLA2gf filter should allow
	SLA files to be viewed on any X-terminal or workstation which
	supports the Xmgf 3D viewing program.

	Known Bugs 

	SLA only supports triangular polygon patches.

	Some CAD systems produce SLA files with the surface
	normals in the wrong direction (for some patches).

	Dan Johnston
	National Research Council of Canada
	1993-July-08
