Vertex Animation Textures

Houdini FX  ·  Unreal Engine 5  ·  VAT Pipeline

Vertex Animation Textures (VAT) allow complex physics simulations to play back in real time at virtually zero GPU cost. Instead of solving physics at runtime, position and rotation data from a Houdini simulation is baked into textures and read by Houdini Engine's VAT shaders inside UE5 — the GPU performs a texture lookup, not a physics solve.

After studying a breakdown by AblazeInt on 80 Level, I replicated the full pipeline to understand how simulation data is encoded, exported, and reconstructed in-engine.

What it demonstrates

  • Full Houdini → UE5 pipeline — export, encode, and decode without any Lab plugins.
  • Shader programming — custom material reconstructs world-space position and rotation per vertex.
  • Runtime optimization — suitable for VR, mobile, and scenes with hundreds of animated instances.

Pipeline

01 · Houdini

Physics simulation

A rigid-body simulation drives the wall collapse. Position (XYZ) and rotation (quaternion) are extracted per vertex, per frame, and prepared for export.

02 · VAT Export

Baking into textures

World-space position and rotation are encoded into the RGB and Alpha channels of two 16-bit float textures. Each row = one frame, each column = one vertex.

03 · UE5 Shader

Real-time reconstruction

A custom material reads the VAT textures, decodes position and rotation, and applies them as a World Position Offset. Zero physics cost at runtime.

Key Takeaways

How simulation data is encoded into textures

Understanding how Houdini packs world-space position and rotation into the pixel channels of a texture — and why texture precision and bounding-box normalization matter for the result.

Houdini Engine → UE5 VAT workflow

Setting up the full export pipeline: simulation, VAT export settings, texture import into UE5, and correct configuration of Houdini's VAT shaders to reconstruct the animation in-engine.

Why VAT outperforms runtime physics

A rigid-body sim in UE5 Chaos scales poorly with object count. VAT reduces runtime cost to a texture lookup per vertex — suitable for VR, mobile, and scenes with many animated instances.

Reading other people's technical work

Studying a professional breakdown and replicating it independently is a core skill in tech art. Understanding why each step exists is what turns a reference into transferable knowledge.

Reflection

The most valuable part of this project was not the result itself but the process of understanding why each step of the VAT pipeline exists. Knowing how simulation data is structured inside a texture — and how the shader reads it back — gives me a mental model I can apply whenever a project needs to trade live computation for pre-baked data, regardless of the simulation type.