Re: LOGO-L> Icosahedron

[KERRB@Magill.UniSA.edu.au]

Regarding the icosohedron / soccer ball shape I just read a chapter in a book 
called 'The jungles of randomness' by Ivars Peterson where he points out that 
this is also the shape of the outer shell of many viruses. Scientists have been 
doing 3D work on this shape with the idea of working out a way to disrupt 
viruses making this shell, as a method of fighting virus infection. Perhaps 
MSWLogo could now be used to simulate this research. 

Thanks George for this fantastic new tool!

-- Bill Kerr
(also the shape of Buckminster Fuller's geodesic dome -- it was Fuller who 
first pointed out that this was the shape of viruses too, in the late 1930's 
and published in 1944 -- from Ch.3 of Peterson's book. Penguin 1988).

I'd love to research this more but no time right now.
------------------------------------------------------

From:	IN%"thl22@cam.ac.uk"  "Tom Lynn" 22-JUL-1998 03:46:50.33

Inspired by the football/soccerball, I've just done an icosahedron.
Unfortunately, while the wireframe looks ok, the solid doesn't really work 
from any viewpoint.  I'm not sure if this is the rendering engine or the 
model itself at fault.

Tom Lynn


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to aaa
	; Draws an icosahedron.
	;
	; Two basic movement primitives are defined.
	; ne (next edge) moves to the next edge clockwise on the current face.
	; nr (next-right) moves to the next face to the right.
	; repeat 5 [nr] returns to the original position.
	;
	; The turtle draws five bars of four triangles around the icosahedron.

	ico 200
end

to fourtri
	make "col :col + 1
	setpc :col
	tri tri ne tri tri
	repeat 2 [nr nr ne]
	nr
end

to ico :size
	; Define some constants
	localmake "phi (1 + sqrt 5) / 2
	localmake "beta arcsin (:phi / sqrt 3)
	localmake "alpha 180-2*:beta ; 180-angle between unconnected vertices of two hinged faces

	cs
	perspective
	ask -1 [setposxyz [100 -500 600]]


	localmake "col 0
	repeat 5 [fourtri]
	polyview
end

to ne
	pu fd :size rt 120
end

to nr
	pu rt 60 fd :size lt 120 rr :alpha
end

to tri
	pd polystart repeat 3 [fd :size rt 120] polyend nr
end


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