從資產檔案編譯和連結 GLSL-ES 著色器

該資產資料夾來儲存你的 GLSL-ES 著色器檔案中的最常見的地方。要在 OpenGL ES 應用程式中使用它們，你需要首先將它們載入到字串中。此函式從資產檔案建立一個字串：

private String loadStringFromAssetFile(Context myContext, String filePath){
    StringBuilder shaderSource = new StringBuilder();
    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(myContext.getAssets().open(filePath)));
        String line;
        while((line = reader.readLine()) != null){
            shaderSource.append(line).append("\n");
        }
        reader.close();
        return shaderSource.toString();
    } catch (IOException e) {
        e.printStackTrace();
        Log.e(TAG, "Could not load shader file");
        return null;
    }
}

現在你需要建立一個函式來編譯儲存在 sting 中的著色器：

private int compileShader(int shader_type, String shaderString){
    
    // This compiles the shader from the string
    int shader = glCreateShader(shader_type);
    glShaderSource(shader, shaderString); 
    glCompileShader(shader);

    // This checks for for compilation errors
    int[] compiled = new int[1];
    glGetShaderiv(shader, GL_COMPILE_STATUS, compiled, 0);
    if (compiled[0] == 0) {
        String log = glGetShaderInfoLog(shader);

        Log.e(TAG, "Shader compilation error: ");
        Log.e(TAG, log);
    }
    return shader;
}

現在你可以載入，編譯和連結著色器：

// Load shaders from file
String vertexShaderString = loadStringFromAssetFile(context, "your_vertex_shader.glsl");
String fragmentShaderString = loadStringFromAssetFile(context, "your_fragment_shader.glsl");

// Compile shaders
int vertexShader = compileShader(GL_VERTEX_SHADER, vertexShaderString);
int fragmentShader = compileShader(GL_FRAGMENT_SHADER, fragmentShaderString);

// Link shaders and create shader program
int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram , vertexShader);
glAttachShader(shaderProgram , fragmentShader);
glLinkProgram(shaderProgram);

// Check for linking errors:
int linkStatus[] = new int[1];
glGetProgramiv(shaderProgram, GL_LINK_STATUS, linkStatus, 0);
if (linkStatus[0] != GL_TRUE) {
    String log = glGetProgramInfoLog(shaderProgram);

    Log.e(TAG,"Could not link shader program: ");
    Log.e(TAG, log);
}

如果沒有錯誤，你的著色器程式就可以使用了：

glUseProgram(shaderProgram);