Asynchronous shader compilation is an Editor-only feature that can improve your workflow when you have complex Shader objects with lots of shader variants.
Shader objects can contain of hundreds or thousands of shader variants. If the Editor compiled all variants when loading a Shader object, the import process would be very slow. Instead, the Editor compiles shader variants on-demand, the first time it encounters them.
Compiling these shader variants can cause the Editor to stall for milliseconds or even seconds, depending on the graphics API and the complexity of the Shader object. To avoid these stalls, you can use asynchronous shader compilation to compile the shader variants in the background, and use placeholder Shader objects in the meantime.
Asynchronous shader compilation works like this:
The following exceptions apply:
CommandBuffer.DrawProcedural, the Editor doesn’t use a placeholder shader. Instead, the Editor just skips rendering this geometry until it has compiled the shader variant.
Asynchronous shader compilation is enabled by default.
To enable or disable asynchronous shader compilation:
Note: Enabling and disabling asynchronous shader compilation in this way affects only the Scene and Game views by default. If you want to use it in other parts of the Editor, see Custom Editor tools and asynchronous shader compilation.
You can enable or disable asynchronous shader compilation for specific rendering commands in your C# scripts.
The following instructions show you how to enable or disable the feature in an immediate scope, and a CommandBuffer scope.
In an immediate scope, you can use
ShaderUtil.allowAsyncCompilationin a variable.
ShaderUtil.allowAsyncCompilationback to its previous state.
Here is a pseudo-code example:
// Store the current state bool oldState = ShaderUtil.allowAsyncCompilation; // Disable async compilation ShaderUtil.allowAsyncCompilation = false; // Enter your rendering code that should never use the placeholder shader Graphics.DrawMesh(...); // Restore the old state ShaderUtil.allowAsyncCompilation = oldState;
ShaderUtil.SetAsyncCompilation, and set it to
false. Subsequent commands in the CommandBuffer won’t allow asynchronous compilation.
Shader.Util.RestoreAsyncCompilationto restore the state of asynchronous shader compilation.
Here is an example:
// Create the CommandBuffer CommandBuffer cmd = new CommandBuffer(); // Disable async compilation for subsequent commands ShaderUtil.SetAsyncCompilation(cmd, false); /// Enter your rendering commands that should never use the placeholder shader cmd.DrawMesh(...); // Restore the old state ShaderUtil.RestoreAsyncCompilation(cmd);
You can disable asynchronous shader compilation for specific Shader objects by forcing the Editor to always compile them synchronously. This is a good option for data generating Shader objects that are always present at the start of your rendering, and which are relatively quick to compile. You would most likely need this if you are performing advanced rendering.
To force synchronous compilation for a Shader object, add the
#pragma editor_sync_compilation directive to your shader source code.
Note: You should not force synchronous compilation for complex Shader objects that encounter new shader variants during rendering; this can stall rendering in the Editor.
You can use C# APIs to monitor the state of asynchronous shader compilation, and perform operations when this state changes.
This is most likely useful in advanced rendering; if the placeholder shader pollutes your generated data, you can wait until compilation is complete, discard the polluted data, and regenerate a new set with the correct shader variants.
If you already know which material you are interested in, you can use
ShaderUtil.IsPassCompiled to check the compilation status of the shader variant. When the status changes Uncompiled to Compiled, compilation is complete.
If you do not know which material you are interested in, or if you are interested in more than one material, you can use
ShaderUtil.anythingCompiling to detect whether Unity is compiling any shader variants asynchronously. When this changes from
false, all current compilation is complete.
Advanced rendering solutions rely on generating data once and reusing it in later frames. If the Editor uses a placeholder shader during this process, it might pollute the generated data. If this happens, you can see the cyan color or other rendering artifacts in your scene, even after the shader variants have finished compiling.
To avoid this, you can:
By default, asynchronous Shader compilation works in the Game and Scene views. If you want to use it in custom Editor tools, you can enable it via C# for your custom tool.
To do this, you can enable asynchronous shader compilation for specific rendering calls.
You can make your custom tools draw something other than the placeholder shader for each material. This way, you can avoid rendering in plain cyan, and instead draw something else while the shader variant compiles.
To check if a specific shader variant has compiled, see Detecting asynchronous shader compilation.
To trigger compilation manually, you can use
ShaderUtil.CompilePass. This way, you can avoid rendering with the cyan placeholder, and draw something else while the shader variant compiles.