LOGO-L> shells in spherical coordinates

[MHELHEFNY@FRCU.EUN.EG]

;Hello Everybody
;Here is the code to draw spherical shells implemented in spherical
;coordinates using sppos library procedure to translate the x,y,z values
;into r,fi,theta values (radius and two angles).
;the drawing is rendered using George Mills's innovation of 3d in
;MswLogo.
;Best regards.
;Mhelhefny
;-----------------------
to go
cs ht pu setsc 0 
setpc [0 0 128]
perspective
sphere2 60 sphere1 100
shade 150 250 40
end

to shade :c :d :e
ask -3 [setxyz :c :d :e]
polyview
end

to sphere1 :a
for [fi 70 180 10][for [theta 0 360 10][
polystart
pd 
sppos :a :fi :theta
sppos :a :fi :theta+10
sppos :a :fi+10 :theta+10
sppos :a :fi+10 :theta 
polyend 
]pu]
end

to sphere2 :a
for [theta 90 180 10][for [fi 0 360 10][
polystart
pd 
sppos :a :fi :theta
sppos :a :fi :theta+10
sppos :a :fi+10 :theta+10
sppos :a :fi+10 :theta 
polyend 
]pu]
end

to sppos :r :fi :theta
setxyz :r*(sin :theta)*cos :fi :r*cos :theta :r*(sin :theta)*sin :fi 
end
;--------------------
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