At design school we're taught to sketch 3D objects on 2D paper, using contour lines to convey three dimensionality to the viewer. But what if those contour lines, rather than serving as visual suggestions, actually served as instructions to a modeling program? In what has to be the most minimalist form of input we've ever seen, a group of researchers has actually worked that out.
A collaboration between the University of Hong Kong, Microsoft Research Asia and the University of British Columbia has yielded "BendSketch: Modeling Freeform Surfaces Through 2D Sketching," a paper presented at this year's SIGGRAPH. Here's how it works:
To model a desired surface patch with our technique, the user sketches the patch boundary as well as a small number of strokes representing the major bending directions of the shape. Our method uses this input to generate a curvature field that conforms to the user strokes and then uses this field to derive a freeform surface with the desired curvature pattern. To infer the surface from the strokes we first disambiguate the convex versus concave bending directions indicated by the strokes and estimate the surface bending magnitude along the strokes. We subsequently construct a curvature field based on these estimates, using a non-orthogonal 4-direction field coupled with a scalar magnitude field, and finally construct a surface whose curvature pattern reflects this field through an iterative sequence of simple linear optimizations.
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Anyone smell a bidding war between the major software companies?