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SECTORL.PI
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1992-09-20
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856b
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36 lines
// Set up the camera
viewpoint {
from <0,2,-5>
at <0,0,0>
up <0,1,0>
angle 30
resolution 160, 160
}
// Set up background color & lights
background SkyBlue
light <10, 20, -30>
include "..\colors.inc"
// Conversion from polar to rectangular (for a left-handed
// coordinate system):
//
// r = sqrt(x^2 + y^2 + z^2),
// theta = atan(y/x),
// phi = atan(sqrt(x^2 + y^2)/z)
//
// Surface is:
// r = 1 + c * LegendreP(3,0,cos(phi))*cos(n*theta)
// r = 1 + c * 2.5 * cos(phi)^3 - 1.5 * cos(phi)
// For this surface, use c = 0.2
// Define a zonal harmonic surface
define theta atan(y/x)
define phi atan(sqrt(x^2 + z^2)/y)
define r sqrt(x^2 + y^2 + z^2)
object {
function r - (1 + (0.5 * cos(phi)^3 - 0.3 * cos(phi)) * cos(3 * theta))
shiny_red
bounding_box <-2, -2, -2>, <2, 2, 2>
}