I was just wondering, is there a way to write a polygon as an equation in 3d? (Yes, a polygon, NOT a polyhedra) It's intended to be a part of a collision detection program, so I need to be able to represent all points on a given polygon as an equation. Each polygon is being acted upon by forces as a function of time, so if I set the distance to 0 and solve for time, I get the time of contact. How can I represent a polygon in such a way? I know the position of all vertices that make up this polygon (and the one it is to be compared to). It looks something like this- Position.A + Velocity.A * Time = Position.B + Velocity.B * Time so, Time = (Position.A-Position.B) / (Velocity.A-Velocity.B) Where position is a polygon and velocity is a vector. It's more complicated than this, but all I need is a way to plug a polygon into position.