Affiliation:
1. University of British Columbia, Canada
2. University of British Columbia, Canada and NVIDIA, Canada
Abstract
Artists often need to
reshape
3D models of human-made objects by changing the relative proportions or scales of different model parts or elements while preserving the look and structure of the inputs. Manually reshaping inputs to satisfy these criteria is highly time-consuming; the edit in our teaser took an artist 5 hours to complete. However, existing methods for 3D shape editing are largely designed for other tasks and produce undesirable outputs when repurposed for reshaping. Prior work on 2D curve network reshaping suggests that in 2D settings the user-expected outcome is achieved when the reshaping edit keeps the
orientations
of the different model elements and when these elements
scale as-locally-uniformly-as-possible (ALUP).
However, our observations suggest that in 3D viewers are tolerant of
non-uniform
tangential scaling if and when this scaling preserves
slippage
and reduces changes in element size, or
scale
, relative to the input. Slippage preservation requires surfaces which are locally
slippable
with respect to a given rigid motion to retain this property post-reshaping (a motion is slippable if when applied to the surface, it slides the surface along itself without gaps). We build on these observations by first extending the 2D ALUP framework to 3D and then modifying it to allow non-uniform scaling while promoting slippage and scale preservation. Our 3D ALUP extension produces reshaped outputs better aligned with viewer expectations than prior alternatives; our slippage-aware method further improves the outcome producing results on par with manual reshaping ones. Our method does not require any user input beyond specifying control handles and their target locations. We validate our method by applying it to over one hundred diverse inputs and by comparing our results to those generated by alternative approaches and manually. Comparative study participants preferred our outputs over the best performing traditional deformation method by a 65% margin and over our 3D ALUP extension by a 61% margin; they judged our outputs as at least on par with manually produced ones.
Publisher
Association for Computing Machinery (ACM)
Subject
Computer Graphics and Computer-Aided Design