Texturing Spheres

Texturing a Sphere

(Pasting a 2D image onto the entire surface of the sphere)

To find which texel in the image the generic hit point maps to,

assume the Generic Hit Point is (GHP.x, GHP.y, GHP.z)
assign theta = acos(GHP.z)
assign phi = atan2(GHP.y, GHP.x)
if (phi < 0.0) then assign phi = phi + 2PI
assign uu = phi/2PI
while (uu > 1.0), assign uu = uu - 1.0
assign vv = (PI - theta)/PI
while (vv > 1.0), assign vv = vv - 1.0
the column of the image texture = (int)(uu * number of columns in the image texture)
the row of the image texture = (int)(vv * number of rows in the image texture)