BlendSim: Simulation on Parametric Blendshapes using Spacetime Projective Dynamics

How to read this

Category

Method: physics-based animation

Contributions

• BlendSim, shifting physics-based animation from discrete frame-by-frame solves to continuous interpolation trajectories built on blendshapes
• Represents each vertex path with continuous, differentiable parametric Bezier splines with variable keyframe times, optimizable to follow physics under constraints
• Uses projective dynamics to decouple the solve into parallelizable local steps and a global quadratic step, supporting collisions and cyclic motion and exporting to glTF

Context

Built on Projective Dynamics, recasting that fast simulation framework in a continuous, blendshape-and-spline trajectory representation rather than per-frame state.Builds on: Projective Dynamics: Fusing Constraint Projections for Fast Simulation

Correctness

The key idea is that a continuous, differentiable spline-on-blendshapes representation can be optimized to satisfy physical laws and constraints; readers should keep in mind that continuous trajectory parameterization trades temporal resolution and keyframe placement against the range of dynamics it can faithfully represent, and check which constraint types and motions were demonstrated.

Clarity

Conceptually crisp framing (continuous vs discrete), but the spacetime projective-dynamics formulation warrants a careful second pass.

How to read it

First pass for the continuous-trajectory reframing and why differentiability matters; second pass on the spacetime projective-dynamics local/global decomposition if you intend to implement, and note the glTF and animation-workflow compatibility as a practical hook.