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Surface Modeling with Oriented Particle System. Szeliski and Tonnesen Siggraph 1992. Overview. Use particle systems to simulate deformable surface models Set up potential functions for internal forces The dynamics controlled by external forces, internal forces, gravity, and damping.
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Surface Modeling with Oriented Particle System Szeliski and Tonnesen Siggraph 1992
Overview • Use particle systems to simulate deformable surface models • Set up potential functions for internal forces • The dynamics controlled by external forces, internal forces, gravity, and damping
Surface Modeling Freeform Surface Modeling
Particle System Oriented Particle System
Oriented Particles Pi: particle (global) position Ri: particles orientation; 3rd column of Ri is the local normal vector Behavior of (oriented) particles is governed by external forces and desired potential functions. Equilibrium states rest at lowest energy state.
Intermolecular Potential Function Dynamics: long-range attraction force and short-range repulsion force pj rij ,fij pi
Weighting Function y (r) The weighting function y (r)is a monotonedecreasing function used to limit the range of inter-particle interactions. Convert to local coordinate
Particle Dynamics • Potential functions specify the “internal forces” • Particle systems are under additional external forces and damping forces
Numerical time integration Euler method, Runge-Kutta, semi-implicit methods, … Controlling Complexity Kd tree to subdivide the tree to efficiently find the neighbors within some radius Rendering Axes, discs, triangulation (wireframe or shaded) Misc.
Modeling Operations Weld two surfaces together
Homework Oriented Particle: 2D version
Summary • State of each particle: • Design potential as in page 7 • Weighting function
Operation • Anchored at two end points; fix one of the normal (q = p/2) • Insert middle points • Deform the curve by moving one middle points • Etc.