LOGO-L> Re: 3D Orange peel with "glitched" removed

["Tom Lynn" <thl22@cam.ac.uk>]

Hi.

George, thanks for fixing the orangepeel glitch.  I've put in an ifelse to 
limit the triangulating to just the glitched area to increase the speed.  
I've removed the moveto procedure too, as it wasn't being used.

Yehuda asked for a version for his gallery which was a bit smaller, so if 
you use "aaa" it will produce this view (attached gif) and "(aaa 1)" will 
produce the previous large view.

On 30 Jul 98, at 20:10, George Mills wrote:

> I did not determine the exact cause because I do not understand Tom's code
> in detail.

Well, in case anyone's interested, the basic method is as follows:

The sphere is built around an imaginary disc, traced out by moving a line 
of length :radius through the steadily increasing angle :r.  As this line 
moves around the disc, there is another imaginary line which is always 
above or below it.  You might think of it as a laser firing onto the inside 
of the sphere, as George describes for his torus.  This line starts 
pointing straight up and moves down through the steadily increasing angle 
:v until it points straight down, but it always moves round to stay above 
or below the first line.  The end of this line traces out the spiral of 
points (marked by turtle zero).

Hanging from this is a washing-line of quadrilaterals.  The height of each 
quadrilateral is half the distance to the washing-line below it.  There are 
special cases at the top and bottom of the sphere where the height 
decreases to zero because the top or bottom of the quadrilateral has 
stopped moving.


Tom
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   ---- File information -----------
     File:  finalfilledpeel.lgo
     Date:  2 Aug 1998, 16:17
     Size:  3476 bytes.
     Type:  Unknown

finalfilledpeel.lgo

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     File:  smallpeel.gif
     Date:  2 Aug 1998, 15:48
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smallpeel.gif