Rendering

Vertex Animation Texture (VAT)

Simulation baked into textures

Also known as: VAT · Vertex animation textures · Houdini VAT · Baked simulation texture · Destruction VAT · Cloth VAT

Definition

A vertex animation texture, or VAT, stores the movement of a mesh's vertices over time in textures, which a vertex shader reads to play the animation. It lets complex simulations, such as destruction, cloth, fluids, soft bodies and morphs, run in real time on the GPU without a skeleton. Houdini provides tools that bake a simulation into position and normal textures and a matching mesh, and engines such as Unreal Engine and Unity play them with a material.

In production

Use VATs for simulations that are the same every time, like a wall breaking or a flag waving, because the result is baked and cannot react to the game. Keep the vertex count and the frame count in check, since the textures grow with both. Check the texture precision, as 8-bit textures give visible stepping, and use 16-bit or half-float formats. They are cheap to play but have to be authored with care.