Shap3d40.dat, 40th 'shape' file for CPO3D
Round hole in a square disc, by users equation.
For information on the option for users equations, see users equations.
See also shap3d37 and shap3d39.
The equations, say g1(x,y,z), for the inner circular edge are
x = r*cos(phi), y = r*sin(phi), z = 0.
The equations, say g2(x,y,z), for the outer square edge are
x = s, y = s*tan(phi), z = 0, where phi = 0 to pi/4.
In the usual fashion we can combine these by using the general equation
g(x,y,z) = (1 - f)*g1 + f*g2,
where f goes from 0 to 1.
This reproduces g1 when f = 0, and g2 when f = 1.
To concentrate the segments near the inner edge, we can use f^2 instead of f.
Here s = 1, r = 0.25, and 3 symmetry planes are used.