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Unity Engine

Use 16-bit precision in shaders

Use 16-bit precision in GPU calculations, so shaders use less memory, bandwidth, and power, and calculations are faster.
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By default, GPUs use 32-bit precision. You can use 16-bit precision instead in GPU calculations, which has the following benefits on mobile platforms:
  • Shaders use less memory, bandwidth, and power.
  • Calculations are faster. Using fewer bits can improve how the GPU allocates registers.

Create a 16-bit variable

To use 16-bit precision in a shader, use 
half
when you declare a scalar, a vector, or a matrix. For example:
half _Glossiness;half4 _Color;half4x4 _Matrix;
注意
Unity doesn't support HLSL floating point suffixes. For example if you use 
2.0h
to create a half precision float, Unity treats it as a high precision float 
2.0f
instead.
To use 16-bit precision in a texture sampler, add 
half4
when you declare it. For example:
Texture2D<half4> _MainTex;
16-bit precision might not be enough for some shader calculations. This might cause visible errors such as color banding or stuttering geometry. To check for errors, run your project on a platform that supports 
half
. If there are errors, use 
float
instead.
A 
half
variable is stored in buffers with a size and alignment of 32 bits.

Use 16-bit values on more platforms

By default, 
half
has no effect on higher performance platforms in Unity, for example platforms that use MacOS. A 
half
variable becomes a 
float
, and the GPU uses 32-bit values for calculations.
To use 16-bit precision on more platforms, go to Edit >
Project Settings

?

> Player and set Shader Precision Model to Uniform. Unity then treats 
half
in your HLSL code as the following:
  • min16float
    for scalars
  • float
    for texture samplers
When Unity compiles shaders, 
min16float
becomes a platform data type that allows the GPU to use 16-bit precision for calculations if it supports them. For example:
  • If you use DirectX 11 or 12, the variable remains a 
    min16float
    .
  • If you use OpenGL, the variable becomes 
    mediump
    .
  • If you use Vulkan, the variable becomes a 
    RelaxedPrecision
    float.
  • If you use Metal, the variable becomes a 
    float
    , but the GPU uses 16-bit values for calculations.
To override the Shader Precision Model setting for textures, add 
_half
when you declare a texture sampler. For example 
Texture2D<half4> _MainTex
.
注意
In versions before Unity 6, the size of 
min16float
varied depending on the target platform if you targeted the Metal graphics API. To enable this behavior in Unity 6 and later, include 
#pragma metal_fxc_allow_float16_in_cpu_visible_buffers
in your shader.

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