{ RCSid $Id: cylmods.cal,v 1.1 2024/12/09 00:44:29 greg Exp $ }
{
	Unit cylinder functions (centered on Z-axis)
	for testing
}
posAngle(a):if(a,a,a+2*PI);

Cx = posAngle(atan2(Py,Px));
Cy = Pz;
Rx(n) = n/(2*PI) * Cx;
Ry(n) = n/(2*PI) * Cy;
Sx(n) = .5*(Rx(n) - Ry(n));
Sy(n) = .5*(Rx(n) + Ry(n));

			{ Checkerboard pattern }
Check(n) = xor(frac(Rx(n))-.5, frac(Ry(n))-.5);

			{ Pyramid texture }
Pyramid_dxy(n) = if(frac(Rx(2*n))-.5, .2, -.2);
Pyramid_dx(n) = -Py*Pyramid_dxy(n);
Pyramid_dy(n) = Px*Pyramid_dxy(n);
Pyramid_dz(n) = if(frac(Ry(2*n))-.5, .2, -.2);