I want to check if a user clicked on a surface. In this case the surface is a coons patch.

What should be the algorithm to finding an intersection of the click point (a ray) with the surface?

I want to check if a user clicked on a surface. In this case the surface is a coons patch.

What should be the algorithm to finding an intersection of the click point (a ray) with the surface?

Maybe you can loop on all the triangles of your surface and use the “raytracing” algorithm. (This is how I do)

Not considering practicality or efficiency you have a surface S(u,v) parameterized by (s,t) and a ray R(u) parameterized by u and you are looking for values s,t,u such that S(s,t) = R(u). In other words you have a system of three equations for three unknowns that you can solve to find the intersection point(s).

I don’t know enough about Coons patches to say if there is a better/different algorithm.