Unreal Engine graphics and text notes: use VAT (vertex animation texture) to make Houdini end on Houdini special effect (ue4/ue5)

disclaimer ： Houdini The small white , Sell now , Pure notes . If there is any misleading, we will not bear any responsibility . This paper refers to Houdini Official 《Lightning Strike FX》 course

Effect demonstration （UE4/5）

What is? VAT？

VAT（Vertex Aniamtion Texture） Vertex animation texture , Its principle is not complicated .VAT It's not for CPU Process the animation , Instead, each vertex displacement data is recorded in the texture , Then input this texture into the world position parameter of the vertex shader , Thus, the GPU Restore the animation of each frame .VAT Not in itself Houdini Invented ,Houdini Based on VAT, A set of Houdini Medium VAT Texture baking method , And help us write support Unreal/Unity Wait for the engine Shader.Houdini Baked VAT The texture is as follows ：

VAT Texture data format is also very simple and intuitive ： The horizontal axis is that each point corresponds to a vertex on the aggregate ; The vertical axis is the time axis . Each point on the plane corresponds to the coordinate displacement of a vertex at a certain time .

Case study ： Crushing effect

0. Overview

1. Geometry node

2. Internal node

2.1 Box node

This is the geometry to be broken , It can be replaced by any mesh model

2.2 RBD Material Fracture node

Scatter Points The larger the value, the more fragmented the mesh will be

2.2 Divide node

2.3 UVTexture node

2.4 Assemble node

2.5 RBD Configure node

adjustment Bound Box Location and size of , The green selected part of the screen is the fragment finally participating in the simulation

2.6 RBD Bulletsolver node

After adding RBD Bulletsolver node It can simulate the crushing

Add ground

Set the position of the ground as required

Create Deforming Static Objects

This step corresponds to using a collision body to collide with the current mesh body

stay Transfer Attribute Add orient and pivot

2.6 Add collider

Place Collider Sphere Through one transform Nodes connecting to RBD BulletSolver Of Collision Geometry entrance

3. Collision animation

4. export VAT

Out Pattern

• "geo" In the folder is fbx Model
• "tex" In the folder are textures