example variations

linear3D 3d
.default {
	<xyz *+= >xyz
}
.

spherivoid 3d {
	radius
}
.default {
	r, theta, phi = spherical >xyz
	r += .radius
	<xyz *+= rect3d r, theta, phi
}
.

elliptic
.priv {
	v
}
.prep {
	.v = >v * 2 / pi
}
.calc {
	tmp, x2 = >y*>y + >x*>x + 1, >x * 2
	xmax = 0.5 * (sqrt (tmp + x2) + sqrt (tmp - x2))
	a = >x / xmax
	b = sqrt (1.0 - a*a)

	<x += .v * atan2 a, b
	if >y > 0 {
		<y += .v * ln (xmax + sqrt (xmax - 1))
	} else {
		<y -= .v * ln (xmax + sqrt (xmax - 1))
	}
}