10 Mar
2008
10 Mar
'08
4:25 a.m.
From: "Bob Bradlee" <caveguy at
sbcglobal.net>
Yes of course this is generally true now that we have floating point
built into nearly every processor, but suppose you using say a Pic
chip to process navigational data, I don't think these have floating
point so fixed point would still be useful. For my work when
programming Microspot Interiors (http://www.microspot.co.uk/products/
interiorsPro/index.htm) I mainly use normalised vectors which I find
far better in 3D systems than angles from the axes, but it is horses
for courses. I also work on MacDraft (http://www.microspot.co.uk/
products/macdraft/index.htm) which is an old 2D program, which used
to store angles in fixed point degrees and I have changed to floating
point degrees, but without rewriting a lot of code and possibly
creating bugs, thats as far as I am going. There are issues using 2Pi
because of rounding errors. Usually you end up having tolerance
values. Without tolerances, if someone rotates something by 90
degrees four times, they don't QUITE get what they started with when
using 2PI, but with degrees, they do.
As for representing an infinite number of angles, don't be silly.
Especially if you are using tolerances.
Roger Holmes,
Technical Director, Microspot Ltd.
> Wouldn't that imply that your system
works off of a basis of 256
> degrees
> instead of 360?
>
In this case, 1/262144 of a circle as it was on
an 18 bit computer,
but today you would probably use 32 bits. There's nothing special
about dividing a circle into 360 parts anyway, 420 would have allowed
2PI are Round!
There are 2Pi radians in a circle, very few in the graphics world
use interger degrees for anything other
than human readable or heman generated I/O. A line is bounded by 2
points or can be described as a
angle and distance from a relitave point. While Arc's can be
specified by a start, end, and center point,
Curves are almost always specified in radians. Autodesk had an
interesting bulge value.
In the graphics world 2 pi are round and can represent an infinate
number of angles, and truely not
square :)