[rescue] FS/FTGH: Sun kit

der Mouse mouse at Rodents.Montreal.QC.CA
Mon Jan 16 23:38:35 CST 2006

> Umm.... just because something has registers labelled X, Y, and Z is
> no reason to infer that it has a "transform engine", if by that term
> you mean the ability to apply 4x4 coordinate matrices to points.

I believe the cg6's "transform engine" is an engine for transforming
(X,Y,Z) three-space coordinates into (X,Y) screen coordinates.  I do
not know whether it is capable of doing perspective transformations (as
opposed to being restricted to parallel projection).

Strictly speaking, I do not know even that much about it, but the
conjecture is fairly strong.

> For instance, the pixel processor chip in Evans & Sutherland's ESV
> workstation (a machine from 1989, so its comparable technology to the
> cg6) has low-level commands that accept X, Y, and Z triplets for
> rasterization of lines and points.  However, there is no transform
> engine in the pixel processor chip -- its just a rasterizer.

Well, call it a rasterizer, if you prefer; what you describe here is a
fairly close match to what I think the cg6 has - or rather, the cg6's
"transform engine" is, I think, *part* of what you're calling a
rasterizer; specifically, the part that converts (X,Y,Z) in three-space
to (X,Y) in screen coordinates.  I call it a transform engine because
that's the term I've seen used for it.  For example, the "TEC" that's
almost universally used to refer to one of the addressible pieces of
the cg6 is, when expanded, always expanded to "Transform Engine
Control", in my experience.

It might be referring to something else, but I am inclined to doubt it.

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