Shader variant stripping

You can prevent shader variants from being compiled. This is called stripping. Stripping unneeded variants can greatly reduce build times, file size, shader loading times, and runtime memory usage. In larger projects, or projects with complex shaders, this is a very important consideration.

If you strip a shader variant that a Material needs at runtime, Unity tries to choose a similar shader variant that’s available. To avoid this, use the following approaches:

• If you use a shader_feature keyword, don’t use the keyword to change which code branch executes at runtime.
• Check what shader variants you have to help you see which shader variants and keyword combinations Materials need at runtime.
• Add shaders to the Always Included Shaders list in Graphics settings.

Limiting shader variants when you declare shader keywords

以下のシェーダーキーワードの宣言方法によって、生成されるバリアントの数を制限することができます。

• Use shader_feature instead of multi_compile where possible - see conditionals in shaders.
• multi_compile で使わないキーワードを定義しないようにします。
• Indicate when shader keywords only affect a given shader stage.

For information on declaring keywords in hand-coded shaders, see Declaring and using shader keywords in HLSL. For information on declaring keywords in Shader Graph, see Shader Graph: Blackboard.

Use preprocessor macros to limit variants by platform

In Unity 2021.3 and above, you can create conditional shader code using a target platform preprocessor macro, so you can limit variants on platforms with limited memory.

The code sample does the following:

• If you build for a SHADER_API_DESKTOP platform, Unity builds variants for every possible keyword combination.
• If you build for another platform, Unity builds only variants for keyword combinations the Materials in your build use.

#ifdef SHADER_API_DESKTOP
   #pragma multi_compile _ RED GREEN BLUE WHITE
#else
   #pragma shader_feature RED GREEN BLUE WHITE
#endif

You can use target platform preprocessor macros to select between shader_feature, multi_compile and dynamic_branch. For more information on when to use each type of conditional, see Shader Conditionals.

Create user-controlled quality settings

When you build for console and mobile platforms that have limited memory, you can limit shader variants by only allowing users to switch between a small number of quality settings.

For example, if you use the keywords DYNAMIC_LIGHTING, SOFT_SHADOWS and HIGH_QUALITY_LIGHTMAPS, you can create the following:

• A ‘low quality’ setting that turns on DYNAMIC_LIGHTING.
• A ‘high quality’ setting that turns on DYNAMIC_LIGHTING, SOFT_SHADOWS and HIGH_QUALITY_LIGHTMAPS.

This means Unity won’t create shader variants for DYNAMIC_LIGHTING when it’s off, or the many different combinations of the 3 keywords being on and off.

You can use target platform preprocessor macros to conditionally create fewer quality settings and fewer variants on platforms with limited memory. For example the following code sample will allow users to switch between 8 permutations of settings on SHADER_API_DESKTOP platforms, but only 2 on SHADER_API_MOBILE platforms.

#if SHADER_API_DESKTOP
   #pragma multi_compile SHADOWS_LOW SHADOWS_HIGH
   #pragma multi_compile REFLECTIONS_LOW REFLECTIONS_HIGH
   #pragma multi_compile CAUSTICS_LOW CAUSTICS_HIGH
#elif SHADER_API_MOBILE
   #pragma multi_compile QUALITY_LOW QUALITY_HIGH
   #pragma shader_feature CAUSTICS // Uses shader_feature, so Unity strips variants that use CAUSTICS if there are no Materials that use the keyword at build time.
#endif

Stripping shader variants in the Editor UI

Unity エディターの UI には、シェーダーストリッピングを設定できる箇所がいくつかあります。

• Graphics Settings ウィンドウ で、Shader stripping セクションの設定を行います。

• Always-included shaders 設定で、必要のないシェーダーが含まれないようにします 。

• GPU インスタンス化、ライトマッピング、フォグに関連するバリアントを除去します。

• ビルトインレンダーパイプラインでは、階層設定が違うことが重要でない場合は、お互いに同じ階層設定にしてください。詳しくは、グラフィックスの階層 を参照してください。

• ユニバーサルレンダーパイプライン (URP)では、URP アセットで使用しない機能を無効にします。詳細は、シェーダーストリッピング を参照してください。

If you use the Universal Render Pipeline you can also do the following:

• In the Universal Render Pipeline Asset, disable rendering any features your project doesn’t use.
• Enable shader stripping.

If you use the High Definition Render Pipeline you can also do the following:

• In the High Definition Render Pipeline Asset, disable any rendering features your project doesn’t use.
• In the Miscellaneous section of the HDRP Global Settings Window, disable Runtime Debug Shaders.

Stripping shader variants using Editor scripts

他の方法では除去できないシェーダーバリアントについては、エディタースクリプトで以下の API を使用してビルド時のストリッピングを行うことができます。

• IPreprocessShaders.OnProcessShader: Unity がグラフィックスシェーダーパスをビルドにコンパイルする前にコールバックを受け取ります。
• IPreprocessComputeShaders.OnProcessComputeShader: receive a callback before Unity compiles a compute shader into a build.

ストリッピングについての詳細は、Unity のブログ スクリプタブルシェーダーバリアントの除去 を参照してください。