Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mandrill!abvax!gfs
From: gfs@abvax.UUCP (Greg F. Shay)
Newsgroups: comp.graphics
Subject: Challenge program #2
Keywords: Assembler vector draw
Message-ID: <369@abvax.UUCP>
Date: 8 Jun 88 15:27:43 GMT
Organization: Allen-Bradley Company, Inc; Industrial Computer Division, Highland Heights, OH
Lines: 29


	I don't know if these challenge proposals are a popular idea.  I am
simply trying to drum up some exchange of ideas, with a motive for finding the
best.  The integer sine program resulted in references to the CORDIC algorithm
which I admit is a better solution for what I was trying to do.

	Here it is,  who can write the fastest code fragment for drawing 2-d
vectors in a bit mapped screen.  My test system has a 68000, and so do
Macintoshes so the 68000 seems to be a good place to start.  Any other micro
is fine too.  The algorithm and clever use of registers is what I am after.

	Vector draw routines involve some setup computations and then an
inner loop that rapidly sets the bits in screen memory.  A tradeoff must be
made since the setup for the fastest inner loop may be longer than the
setup for a slightly slower inner loop which will cause a difference in
overall performance depending on the average length of the vector drawn.
For arguments sake, unless someone knows of a better number, assume the
average length of a vector drawn is about 50 pixels.
	
	I'll post my 68000 assembler code later.  For now, I'll say the
innermost loop takes an average of 51 machine clocks per pixel (8 instructions).
At 8 Mhz, this would be 6.375 microseconds per pixel or 157,000 pixels/sec.

	Have fun!
		Greg Shay

	..mandrill  |
	..pyramid   |..!abvax!gfs
	..decvax    |