1. A process for simulating and assembling flexible parts, comprising: creating an ideal path between first and second planes; placing a virtual rigid envelope around the ideal path from the first plane to the second plane; marking a virtual flexible part with reference features; pulling the virtual flexible part through the virtual rigid envelope, such that the path of the virtual flexible part is constrained by the virtual rigid envelope, wherein the virtual flexible part is not constrained from rotating within the virtual rigid envelope; removing the virtual rigid envelope and allowing the virtual flexible part to relax; and marking first and second end conditions on the virtual flexible part corresponding respectively to an intersection of the reference features with the first and second planes.