RE: circle-segments

• To: rick@maxai.den.mmc.com (Rick Duffy), miller@cam.nist.gov, nicolai@gate.fzi.de
• Subject: RE: circle-segments
• From: miller@cam.nist.gov (Bruce R. Miller)
• Date: Mon, 16 Dec 1991 15:40-0500
• Cc: clim@BBN.COM
• In-Reply-To: <9112161330.AA17022@maxai>

    Date: Mon, 16 Dec 1991 08:30 EST
    From: Rick Duffy <rick@maxai.den.mmc.com>

	  ;Hello CLIMer,
	  ;I have some troubles with the drawing-circle function. It works well, if
	  ;I want to draw full circles, not specifying start- and end-angle. If I
	  ;give values to these keywords the debugger always tells me:

	  ;Trap: The function CLIM-UTILS::NYI is undefined.
	   ...
    ...

    I'm having the same problem you are - maybe the cad demo works because it draws
    half-circles (maybe only pi-aligned angles work - haven't checked yet).

Well, since noone authoritative has answered yet, I'll stick my neck out
a bit further :>

Dissasembling gives a few clues, although I'm pretty poor at deciphering
assembly code.
It seems not to be the case that start & end angles are NYI.  Rather
only some special cases are.
It seems what happens is:
  If the current transformation is a reflection, start & end get
swapped.
  The difference d=end-start is computed.
  If abs(d) < 0, [I said I didn't understand assembly !]  NYI gets
called.
  If d > 2pi, NYI gets called.

Well, assuming that the true code actually makes sense, perhaps the
problem is that in your example you have end(1/2 pi) < start (3/2 pi).
Maybe you should trye end = 5/2 pi (or whatever you meant, but
with end>start).
The doc says that the arc is drawn counter clockwise.  

bruce
miller@cam.nist.gov

0,,

• RE: circle-segments
• From: Rick Duffy <rick@maxai.den.mmc.com>

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