ShaderLab command: Blend

Determines how the GPU combines the output of the fragment shaderA program that runs on the GPU. More info
See in Glossary with the render target.

The functionality of this command depends on the blending operation, which you can set using the BlendOp command. Note that while blending itself is supported on all graphics APIs and hardware, some blending operations have more limited support.

Enabling blending disables some optimizations on the GPU (mostly hidden surface removal/Early-Z), which can lead to increased GPU frame times.

Render pipeline compatibility

Usage

This command makes a change to the render state. Use it in a Pass block to set the render state for that Pass, or use it in a SubShader block to set the render state for all Passes in that SubShader.

If blending is enabled, the following occurs:

• If the BlendOp command is used, the blending operation is set to that value. Otherwise, the blending operation defaults to Add.
• If the blending operation is Add, Sub, RevSub, Min, or Max, the GPU multiplies the value of the output of the fragment shader by the source factor.
• If the blending operation is Add, Sub, RevSub, Min, or Max, the GPU multiplies the value that is already in the render target by the destination factor.
• The GPU performs the blending operation on the resulting values.

The blending equation is:

finalValue = sourceFactor * sourceValue operation destinationFactor * destinationValue

In this equation:

• finalValue is the value that the GPU writes to the destination buffer.
• sourceFactor is defined in the Blend command.
• sourceValue is the value output by the fragment shader.
• operation is the blending operation.
• destinationFactor is defined in the Blend command.
• destinationValue is the value already in the destination buffer.

Notes:

1. Any signature that specifies a render target requires OpenGL 4.0+, GL_ARB_draw_buffers_blend, or OpenGL ES 3.2.
2. Separate RGB and alpha blending is not compatible with advanced OpenGL blending operations.

Valid parameter values

Common blend types

Here is the syntax for the most common blend types:

Blend SrcAlpha OneMinusSrcAlpha // Traditional transparency
Blend One OneMinusSrcAlpha // Premultiplied transparency
Blend One One // Additive
Blend OneMinusDstColor One // Soft additive
Blend DstColor Zero // Multiplicative
Blend DstColor SrcColor // 2x multiplicative

Examples

Shader "Examples/CommandExample"
{
    SubShader
    {
         // The rest of the code that defines the SubShader goes here.

        Pass
        {    
              // Enable regular alpha blending for this Pass
      Blend SrcAlpha OneMinusSrcAlpha
            
              // The rest of the code that defines the Pass goes here.
        }
    }
}

This example code demonstrates the syntax for using this command in a SubShader block.

Shader "Examples/CommandExample"
{
    SubShader
    {
         // Enable regular alpha blending for this SubShader
         Blend SrcAlpha OneMinusSrcAlpha

         // The rest of the code that defines the SubShader goes here.        

        Pass
        {    
              // The rest of the code that defines the Pass goes here.
        }
    }
}