   Simple Face Intersection
  Can anyone help me?I have an arbitary point in X, Y, Z Coordinate Space, say P0,  and set of points defining a Face (approximately in same Plane but not necessarily), say F. I would like to project the point P0 onto the defined Face but don't exactly what I should do - I think I need to shoot a ray to the Face?Can anybody send me a link to some information on this (or simple code)? Also the point P0 could be anywhere in the coordinate space relative to the Face - in front, behind, parallel, etc.Many thanks.   
  I think you'll need to provide some more information, such as what the points represent exactly, and where the point data comes from. As is, it doesn't sound like the problem is well-defined (it sounds like you're asking how to project a point orthgonally onto a surface, but you don't have a definition for the surface - only a set of points that may or may not be coplanar).   ;  I guess the point should represent the origin of a ray that should shoot in the direction of a defined surface to compute the intersection.Thank you for the reply.   ;Quote:I guess the point should represent the origin of a ray that should shoot in the direction of a defined surface to compute the intersection.Projecting a point onto a surface is different (in general) than intersecting a ray with that surface, so first you'll need to decide which it is you want to do. If it's a ray intersection you want, you'll also need to determine the ray direction.The other part of the problem is the surface itself. You say you have a set of points, but that they're not necessarily coplanar. What sort of surface do they define? Are they triangulated? Do they 'almost' lie in the same plane and form a polygon in that plane? Is the polygon convex? Do you have access to the definition of the plane?I may be missing something obvious here, but thus far I don't think you've provided enough information for us to be able to help you solve the problem.   