Version: 2020.3
ShaderLab: legacy texture combining
HLSL in Unity

ShaderLab: legacy vertex data channel mapping

Note: The ShaderLabUnity’s language for defining the structure of Shader objects. More info
See in Glossary
functionality on this page is legacy, and is documented for backwards compatibility only. If your shaderA program that runs on the GPU. More info
See in Glossary
source file includes HLSL code, Unity ignores these commands completely. If your shader source file does not include HLSL code, Unity compiles these commands into regular shader programs on import.

Render pipeline compatibility

Feature name Built-in Render PipelineA series of operations that take the contents of a Scene, and displays them on a screen. Unity lets you choose from pre-built render pipelines, or write your own. More info
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Universal Render Pipeline (URP) High Definition Render Pipeline (HDRP) Custom SRP
Legacy vertex data channel mapping Yes No No No

Overview

The BindChannels command allows you to specify how vertex data maps to the graphics hardware. By default, Unity figures out the bindings for you, but in some cases you want custom ones to be used.

For example you could map the primary UV set to be used in the first texture stage and the secondary UV set to be used in the second texture stage; or tell the hardware that vertex colors should be taken into account.

Syntax

BindChannels { Bind "source", target }

Specifies that vertex data source maps to hardware target.

Source can be one of:

  • Vertex: vertex position
  • NormalThe direction perpendicular to the surface of a mesh, represented by a Vector. Unity uses normals to determine object orientation and apply shading. More info
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    : vertex normal
  • Tangent: vertex tangent
  • Texcoord: primary UV coordinate
  • Texcoord1: secondary UV coordinate
  • Color: per-vertex color

Target can be one of:

  • Vertex: vertex position
  • Normal: vertex normal
  • Tangent: vertex tangent
  • Texcoord0, Texcoord1, …: texture coordinates for corresponding texture stage
  • Texcoord: texture coordinates for all texture stages
  • Color: vertex color

Details

Unity places some restrictions on which sources can be mapped to which targets. Source and target must match for Vertex, Normal, Tangent and Color. Texture coordinates from the meshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
See in Glossary
(Texcoord and Texcoord1) can be mapped into texture coordinate targets (Texcoord for all texture stages, or TexcoordN for a specific stage).

There are two typical use cases for BindChannels:

  • Shaders that take vertex colors into account.
  • Shaders that use two UV sets.

Examples

// Maps the first UV set to the first texture stage
// and the second UV set to the second texture stage
BindChannels {
   Bind "Vertex", vertex
   Bind "texcoord", texcoord0
   Bind "texcoord1", texcoord1
}
// Maps the first UV set to all texture stages
// and uses vertex colors
BindChannels {
   Bind "Vertex", vertex
   Bind "texcoord", texcoord
   Bind "Color", color
}
ShaderLab: legacy texture combining
HLSL in Unity