Unity's IPreprocessShaders: in-depth analysis and practical cases

Unity IPreprocessShaders

Unity IPreprocessShaders is a very useful function in the Unity engine, which allows developers to customize which operations need to be performed when compiling Shader. This can help developers better control the Shader compilation process and ensure that the necessary operations are performed when compiling the Shader. In this article, we introduce how to use Unity IPreprocessShaders, and provide three usage examples to help readers better understand this function.

How to use Unity IPreprocessShaders

Unity IPreprocessShaders is an interface that is called when compiling Shader. In this port, we can write the operations we need to perform, and we can get the current Shader. Here is a simple example that demonstrates how to perform some operations when compiling a shader:

using UnityEngine;
using UnityEditor;
using UnityEditor.Build;
using UnityEditor.Build.Reporting;

public class ShaderPreprocessor : IPreprocessShaders
{
    public int callbackOrder { get { return 0; } }

    public void OnProcessShader(Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> shaderCompilerData)
    {
        // Do something with the shader
    }
}

In this example, we implement the IPreprocessShaders interface and override its OnProcessShader method. In this method, we can get the current Shader and perform the operations we need to perform.

Example of use

Below are three examples of using Unity IPreprocessShaders, each of which provides a concrete implementation.

Example 1: Modify the properties of Shader

In this example, we will demonstrate how to modify Shader properties.

using UnityEngine;
using UnityEditor;
using UnityEditor.Build;
using UnityEditor.Build.Reporting;

public class ShaderPreprocessor : IPreprocessShaders
{
    public int callbackOrder { get { return 0; } }

    public void OnProcessShader(Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> shaderCompilerData)
    {
        if (snippet.passType == PassType.ForwardBase)
        {
            foreach (var data in shaderCompilerData)
            {
                data.shaderCompilerOptions.Add("d3d11_no_compute_shaders", "true");
            }
        }
    }
}

In this example, we implement the IPreprocessShaders interface and override its OnProcessShader method. In this method, we first determine whether the current Shader is of ForwardBase type. Then, we loop through all ShaderCompilerData and add an option to their shaderCompilerOptions.

Example 2: Disable Shader compilation

In this example, we will demonstrate how to disable Shader compilation.

using UnityEngine;
using UnityEditor;
using UnityEditor.Buildusing UnityEditor.Build.Reporting;

public class ShaderPreprocessor : IPreprocessShaders
{
    public int callbackOrder { get { return 0; } }

    public void OnProcessShader(Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> shaderCompilerData)
    {
        if (shader.name == "MyShader")
        {
            shaderCompilerData.Clear();
        }
    }
}

In this example, we implement the IPreprocessShaders interface and override its OnProcessShader method. In this method, we first judge whether the current Shader is "MyShader". Then, we clear all ShaderCompilerData, thus disabling Shader compilation.

Example 3: Modify Shader's code

In this example, we will demonstrate how to modify the Shader's code.

using UnityEngine;
using UnityEditor;
using UnityEditor.Build;
using UnityEditor.Build.Reporting;

public class ShaderPreprocessor : IPreprocessShaders
{
    public int callbackOrder { get { return 0; } }

    public void OnProcessShader(Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> shaderCompilerData)
    {
        if (shader.name == "MyShader")
        {
            foreach (var data in shaderCompilerData)
            {
                data.shaderCompilerOptions.Add("MY_DEFINE", "1");
                data.shaderCompilerOptions.Add("MY_COLOR", "float4(1, 0, 0, 1)");
                data.shaderCompilerOptions.Add("MY_TEXTURE", "myTexture");
                data.shaderCompilerOptions.Add("MY_MATRIX", "UNITY_MATRIX_MVP");
                data.shaderCompilerOptions.Add("MY_FLOAT", "1.0");
            }
        }
    }
}

In this example, we implement the IPreprocessShaders interface and override its OnProcessShader method. In this method, first determine whether the current Shader is "MyShader". Then, we traverse all ShaderCompilerData and add some options to their shaderCompilerOptions, thus modifying the Shader code.

in conclusion

Unity IPreprocessShaders is a very useful function that can help developers better control the Shader compilation process and ensure that the necessary operations are performed when compiling the Shader. In this article, we introduce the method of Unity IPreprocessShaders and provide three usage examples to help readers better understand this function. Hope this article is helpful to readers.

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