From:	Ludvig Larsson <ludvig AT club-internet DOT fr>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: 3d sphere
Date:	Sat, 17 Oct 1998 05:57:23 +0200
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jud wrote:
> 
> i came up with an idea of the idea of making a program that will draw a
> sphere out of a series of lines. This lines will be the size of the
> perimeter of the sphere. There will be the same amount of these "ribbons" as
> there are pixels in the hieght of the sphere.
> 
> The problem here is i havent taken anything above algebra 1, although i have
> some basic ideas about sine cosine and arctangent funtions. A problem arises
> that if you take the half of the "ribbon" you have to make it shrink more
> and more as it geos from the middle of the sphere around, i dont know the
> formula to do this and i need it so i can show the sphere on the screen and
> have it look realistic

Phew...
I'll guess that maybe I can give you a hint...

If you are not speed dependen, make two loops:
loop b=0° to 180°
 loop a=0° to 180°
  ribbon=cos(b)
  offset in ribbon=cos(a)
  screenpos= (a,b)

offcourse you have to multiply a and b with different konstants,
bependin on how many ribbons you have, how big they are and the size of
the sphere on screen.

cos(a) and cos(b) witt ossilate between -1 and 1 so if you want a screen
x-size of 100, make screen_x=cos(a)*50+50;

Hop it helped(and hope it works, BTW, ordinary sin() and cos() works
with radians, radians=degrees*pi/180 so use sin(a*3.1415/180) etc).

Ludvig Larsson

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