[rescue] FS/FTGH: Sun kit

der Mouse mouse at Rodents.Montreal.QC.CA
Tue Jan 17 00:50:35 CST 2006

>> I believe the cg6's "transform engine" is an engine for transforming
>> (X,Y,Z) three-space coordinates into (X,Y) screen coordinates.
> Why do you believe this?

Because the designers said so. :-)

I finally went digging, and found I have a copy of an article that
appeared in IEEE Micro in 1990, if the page footers are to be believed,
written by Curtis R. Priem of Sun, titled "Developing the GX Graphics
Accelerator Architecture".  It says of the TEC (the "Transformation
Engine and Cursor" chip) that it

	... contains a 64-register file and a 32-bit, signed
	multiply/accumulator, which ... provide arithemtic ... at a
	rate of up to [50 MFLOPS].

	The TEC includes explicit support for the typical 2D and 3D
	graphics-transformation pipeline.  The modeling and viewing, or
	MV, matrix can consist of anything from a simple 3x2 matrix
	used by 2D graphics to a 4x4 matrix used by 3D graphics.  ...
	optional clip checking ... viewing pyramid for 3D graphics ...
	also provides an optional perspective divide function ...

	At the end of the pipeline, an optional matrix (the virtual
	device coordinate) transforms the coordinates into the final
	screen-coordinate space.  The host can read and/or
	automatically load transformation results into the FBC [the
	"Frame Buffer Controller" chip] for rendering.  The host also
	has access to intermediate pipeline results.

	... data formats ... signed integer, [16+16 fixed-point], or
	IEEE-754 single-precision ...  The TEC accepts both absolute
	and relative 3D (x,y), 3D (x,y,z), and homogenous (x,y,z,w)
	coordinate data.  Since the TEC's math capability extends to
	general-purpose vector operations, it calculates the arithmetic
	required for matrix concatenation, dot products, lighting
	models, and even some common imaging operations such as

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