/usr/share/radiance/ball.cal is in radiance-materials 4R1+20120125-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | {
ball.cal - 2d coordinate mapping onto sphere.
unit sphere centered at origin
A1 = picture height/width
A2 = unit scale for pattern
}
ball_u = Atan2(Py,Px)*Sqrt(1-Pz*Pz)/A2;
ball_v = Acos(Pz)/A2;
ball_tile_u = mod(ball_u,max(1,1/A1));
ball_tile_v = mod(ball_v,max(1,A1));
ball_match_u = tri(ball_u,max(1,1/A1));
ball_match_v = tri(ball_v,max(1,A1));
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