While it might not seem like it, these virtual pieces of rope are closely related to motion paths for the robot arm. Quaternions, interpolation, matrix computations, all of it.
Software
Robot Simulation Labs
Stereo IR Tracker
DIY Stereo infrared tracker based on modified Sony Playstation Eye cameras.
Quick demo rendering image at average position from both cameras and scale based on disparity between images.
CAM Processing
Volumetric CAM processor v1 (still pretty rough). Test model generated in Openscad, resulting g-code file visualized in LinuxCNC.
Test Model 
Rough Pass (Horizontal) 
Rough Pass (Vertical) 
Contouring 
Surface (Horizontal) 
Surface (Vertical)
Photogrammetry Experiments
Giving Meshroom a try and printing the result. The model needs to be cleaned up a bit though.
