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.PS
# Cruller.m4
threeD_init
NeedDpicTools
scale = 2.54
define(`lobe',`(sind(6*(`$1'))+4)/5*2.25')
viewazimuth = 20 # Set view angles in degrees
viewelevation = 30
setview(viewazimuth,viewelevation,0)
dt = 3 # major angle degrees per facet
ds = 10 # minor angle degrees per facet
tradius = 6
define(`cruller',`rot3Dz((`$1')*dtor_,
sum3D(0,tradius,0,0,Rect_(lobe(`$2'+2*(`$1')),`$2')))')
define(`tvisible',`dot3D(View3D,
cross3D(diff3D(cruller(`$1'+dt/2,`$2'),cruller(`$1',`$2')),
diff3D(cruller(`$1',`$2'+ds/2),cruller(`$1',`$2'))))')
# create the arrays and sort
n = 0
for t = dt to 360+dt/2 by dt do {
for s=ds/2 to 360.1 by ds do {
if tvisible(t,s) > -0.01 then {
n +=1
t[n] = t
s[n] = s
d[n] = dot3D(cruller(t,s),view3D1,view3D2,view3D3) # view distance
ix[n] = n
}
} }
# prval(n)
dpquicksort(d,1,n,ix)
# Background
Bne: (9,6)
Bsw: (-9,-6)
B: 0.5 between Bne and Bsw
iflatex(`line fill_(0.75) \
from (Bsw,Bne) to Bsw then to (Bne,Bsw) then to Bne then to (Bsw,Bne)',
`ShadedPolygon((Bsw,Bne):Bsw:(Bne,Bsw):Bne,,-30,
0,1,1,1,
.5,.1,.4,0,
1,0,0,0) at B')
# draw the facets
thinlines_
[
rgbtohsv(0.6,0.4,0,h,s,v)
for i = 1 to n do {
tc = t[ix[i]]; sc = s[ix[i]]
SE: (Project(cruller(tc+dt/2,sc-ds/2)))
SW: (Project(cruller(tc-dt/2,sc-ds/2)))
NW: (Project(cruller(tc-dt/2,sc+ds/2)))
NE: (Project(cruller(tc+dt/2,sc+ds/2)))
f = ((dcosine3D(3,cruller(tc,sc))/2.25+1)/2)^2
hsvtorgb(h,(1-f)*s,1,r,g,b)
line outlined rgbstring(r,g,b) shaded rgbstring(r,g,b) ifpdf( invis ) \
from SE to SW then to NW then to NE then to SE }
] at B
thicklines_
.PE
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