https://github.com/keijiro/HdrpVatExample

VAT (Vertex Animation Texture) with Unity Shader Graph and Visual Effect Graph
https://github.com/keijiro/HdrpVatExample

houdini unity unity3d vat vfx vfxgraph

Last synced: 15 days ago
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VAT (Vertex Animation Texture) with Unity Shader Graph and Visual Effect Graph

• Host: GitHub
• URL: https://github.com/keijiro/HdrpVatExample
• Owner: keijiro
• License: unlicense
• Created: 2019-12-17T10:19:32.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2021-12-15T22:34:27.000Z (over 3 years ago)
• Last Synced: 2024-08-02T13:33:11.633Z (10 months ago)
• Topics: houdini, unity, unity3d, vat, vfx, vfxgraph
• Language: HLSL
• Homepage:
• Size: 76.1 MB
• Stars: 871
• Watchers: 28
• Forks: 86
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
VAT (Vertex Animation Texture) on Unity HDRP examples

=====================================================

This is a repository that contains examples of the use of VAT (Vertex Animation

Texture) on Unity High Definition Render Pipeline (HDRP).

In this document, "VAT" refers explicitly to the texture encoding method used

in Houdini and [SideFX Labs].

[SideFX Labs]: https://github.com/sideeffects/SideFXLabs

![gif](https://i.imgur.com/Ctsa3av.gif)

![gif](https://i.imgur.com/rYmtjLZ.gif)

![gif](https://i.imgur.com/n4WL4Qy.gif)

![gif](https://i.imgur.com/idCLijy.gif)

*Several types of VAT: Soft, Rigid, Fluid and Sprite*

System requirements

-------------------

- Unity 2019.4

- HDRP 7.4

How to use VAT with Shader Graph

--------------------------------

At first, export VAT files from Houdini. It consists of a geometry file

(`.fbx`), texture files (`.exr`) and a realtime data file (`.json`). Then

import `.fbx` and `.exr` files into Unity. The texture files must be imported

with the following settings:

- sRGB (Color Texture): Off

- Non-Power of 2: None

- Generate Mip Maps: Off

- Format: "Automatic" is recommended. You can select a lower BPP format with

  sacrificing quality.

- Compression: "None" is recommended. You can try other options, but usually,

  they don't work with non-power of two textures.

![importer](https://i.imgur.com/01SK60b.png)

There are three types of shader graphs under the "Shader Graph" group: Soft,

Rigid, and Fluid. You can use corresponding VAT methods with these shader

graphs.

These shader graphs have some VAT dependent properties.

![material](https://i.imgur.com/tyLWdYQ.png)

The "\_numOfFrames", "\_posMax" and "\_posMin" properties must be set based on

the realtime data. Open the exported `.json` file with a text editor and

copy-paste these values to the corresponding properties.

You can use the packed-normal encoding (the "Pack normals into Position Alpha"

option in the VAT exporter) with enabling the "Use Packed Normals" option in

the material settings. Note that this may significantly increase the

quantization errors in normal vectors.

To animate the mesh, you have to control the "Current Frame" property manually.

Using a timeline would be the handiest way to do it.

The structure of the shader graph is quite simple. You can easily extend it to

add features, like adding a albedo map or support of different surface types.

For example, an extended shader graph named "Soft Lerp" is used in the Soft

example, that interpolates positions/normals between consecutive frames to

achieve smooth animation.

How to use VAT with Visual Effect Graph

---------------------------------------

You can use a Sprite VAT to move particles in a Visual Effect graph; Other

methods are not supported at the moment.

This project contains the following three subgraph operators that are designed

to be used with VAT.

**VAT Particle Count** -- Calculates the number of particles contained in VAT.

This is convenient to determine the number of particles to emit in the Spawn

context.

**VAT Particle UV** -- Calculates the texture coordinates for each particle.

This can be used to retrieve data from a position map.

**VAT Convert Position** -- Converts position data into a object space position

vector.

For detailed usage of these operators, see Sprite example in this project.

Frequently Asked Questions

--------------------------

#### Is it possible to support Universal RP?

Yes. Although these examples are created with HDRP, you can use the same

approach on Universal RP. These shader graphs and VFX graphs can be converted

by changing a few options. Check [the URP branch] for details.

[the URP branch]: https://github.com/keijiro/HdrpVatExample/tree/urp