9 to 5

Overview

A photogrammetry-scanned sneaker crashes through a glass pane, shattering it outward in a Matrix-style ripple pattern — constraints break from the impact center outward like a shockwave, pieces explode with no gravity, and mist trails behind. The ripple deformation on the glass was done in Blender before export, while all fracture, simulation, debris, and mist were handled in Houdini.

The Matrix Ripple Glass

The glass pane was pre-deformed in Blender with a ripple/wave modifier before export. This gives the glass its Matrix helicopter-into-skyscraper look — the surface has concentric wave distortion baked into the mesh, so when it fractures in Houdini the shards inherit that curved ripple shape. The effect is geometry-level, not simulation-level.

Houdini RBD Glass Fracture Pipeline

The core of the effect. Before fracturing, the glass is split into two groups using an Attribute Wrangle — only the area near the impact gets fractured, the rest stays intact. This keeps the sim fast and avoids unnecessary pieces at the edges.

The fracture uses RBD Material Fracture set to Glass mode with scatter-based impact points and convex decomposition for accurate Bullet collision shapes. No chipping — clean glass breaks only.

Distance-Based Constraint Propagation

The most important custom technique in the scene. A VEX wrangle drives constraint strength based on distance from the impact center, creating wave-like propagation where glass breaks from the center outward.

The square-root curve makes the initial spread fast and dramatic near the center, then slows toward the edges — mimicking a shockwave that decelerates as it radiates outward.

Frame-Gated Explosion Velocity

A VEX wrangle applies radial outward push starting at frame 38 with strength 8.0. Nothing moves until impact, then pieces explode outward. The falloff radius is intentionally tight (0.9 units) so only pieces near the impact center get the strongest kick. A slight +Y bias gives natural upward lift to center shards.

RBD Bullet Solver Settings

POP Debris System

Small glass shards that fly off the main fracture, sourced from the sim velocity. The pipeline runs through a Debris Source into a POP network with gravity, wind force for drift, and VDB collision from the glass surface. Platonic solids are copied to points for tiny shard shapes with randomized scale and rotation per particle. Short lifespan (0.2s) keeps them as quick sparkle particles.

Pyro Mist Simulation

A fine mist cloud that follows the glass explosion, giving it atmospheric bullet-time haze. Sourced from the debris source points of the glass sim so smoke appears exactly where glass is breaking.

Techniques & Nodes

Houdini → Blender Export Pipeline