Sculpting by Numbers

Sculpting guidance: A user is given feedback during sculpting by two forms of guidance projected onto the model, which they can toggle between. Guidance is computed by comparing the target depth map (a) to the scanned depth map of the current shape (b). Depth guidance (c) illustrates the difference between the two maps and is helpful for matching the position of the surface in absolute 3D coordinates. Edge guidance (d) illustrates the second derivative of the target model (i.e. ridges and valleys), and is useful for recreating fine details once the model is close to the target shape. A smoothly-varying range of colors is used: in depth mode green indicates where the surface should be moved closer to the scanner and red farther, while in edge mode green indicates a positive second derivative (a ridge) and red negative (a valley). In either mode, blue indicates background, so any part of the material colored blue should be removed entirely.


Alec Rivers, MIT CSAIL
Andrew Adams, MIT CSAIL
Frédo Durand, MIT CSAIL


We propose a method that allows an unskilled user to create an accurate physical replica of a digital 3D model. We use a projector/camera pair to scan a work in progress, and project multiple forms of guidance onto the object itself that indicate which areas need more material, which need less, and where any ridges, valleys or depth discontinuities are. The user adjusts the model using the guidance and iterates, making the shape of the physical object approach that of the target 3D model over time. We show how this approach can be used to create a duplicate of an existing object, by scanning the object and using that scan as the target shape. The user is free to make the reproduction at a different scale and out of different materials: we turn a toy car into cake. We extend the technique to support replicating a sequence of models to create stop-motion video. We demonstrate an end-to-end system in which real-world performance capture data is retargeted to claymation. Our approach allows users to easily and accurately create complex shapes, and naturally supports a large range of materials and model sizes.


The authors wish to thank Abe Davis, Elena Adams, and the user study participants. The work was partially funded by NSF grant 0964004, Foxconn, and a gift from Cognex.


Sculpting by Numbers (10mb)
Alec Rivers, Andrew Adams, Frédo Durand.
SIGGRAPH Asia 2012.