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Technical Papers
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Non-linear sphere tracing for rendering deformed signed distance fields
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Technical Papers
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TimeWednesday, 20 November 201911:42 - 12:03
DescriptionSigned distance fields (SDFs) are a particularly powerful implicit representation for modeling solids, volumes and surfaces. Their infinite resolution, controllable continuity, and robust constructive solid geometry operations, coupled with smooth blending, have enabled powerful and intuitive sculpting tools for creating complex SDF models. Their metric properties also allow efficient surface rendering via sphere tracing. Unfortunately, SDFs remain incompatible with many popular direct deformation techniques which re-position a surface via its explicit representation. Linear blend skinning used in character articulation, for example, directly displaces each vertex of a triangle mesh. To overcome this limitation, we propose a variant of sphere tracing for directly rendering deformed SDFs. We show that this problem reduces to integration of a non-linear ordinary differential equation (ODE). We propose an efficient approach with controllable error which first automatically computes an initial value along each cast ray and then walks conservatively along the curved ray in the undeformed space according to the signed distance. Importantly, our approach does not require knowing, computing, or even the global existence of the inverse deformation, which allows us to plug in many existing forward deformations with relative ease. We demonstrate the effectiveness of this approach for interactive rendering of a variety of popular deformation techniques that were so far limited to explicit surfaces.