opengl
Shader लोड हो रहा है और संकलन

परिचय

टिप्पणियों

सी ++ में अलग होने योग्य लोड करें

#include <string>
#include <fstream>

//In C++17, we could take a `std::filesystem::path` instead of a std::string
//for the filename.
GLuint CreateSeparateProgram(GLenum stage, const std::string &filename)
{
    std::ifstream input(filename.c_str(), std::ios::in | std::ios::binary | std::ios::ate);
    
    //Figure out how big the file is.
    auto fileSize = input.tellg();
    input.seekg(0, ios::beg);
    
    //Read the whole file.
    std::string fileData(fileSize);
    input.read(&fileData[0], fileSize);
    input.close();
    
    //Compile&link the file
    auto fileCstr = (const GLchar *)fileData.c_str();
    auto program = glCreateShaderProgramv(stage, 1, &fileCstr);

    //Check for errors
    GLint isLinked = 0;
    glGetProgramiv(program, GL_LINK_STATUS, &isLinked);
    if(isLinked == GL_FALSE)
    {
        //Note: maxLength includes the NUL terminator.
        GLint maxLength = 0;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &maxLength);        

        //C++11 does not permit you to overwrite the NUL terminator,
        //even if you are overwriting it with the NUL terminator.
        //C++17 does, so you could subtract 1 from the length and skip the `pop_back`.
        std::basic_string<GLchar> infoLog(maxLength);
        glGetProgramInfoLog(program, maxLength, &maxLength, &infoLog[0]);
        infoLog.pop_back();

        //The program is useless now. So delete it.
        glDeleteProgram(program);

        //Use the infoLog in whatever manner you deem best.

        //Exit with failure.
        return 0;
    }
    
    return program;
}

C ++ में व्यक्तिगत शेडर ऑब्जेक्ट संकलन

पारंपरिक GLSL संकलन मॉडल में एक shader चरण के लिए एक shader ऑब्जेक्ट में संकलन कोड शामिल होता है, फिर एक ही प्रोग्राम ऑब्जेक्ट में कई shader ऑब्जेक्ट्स को जोड़ना (उन सभी चरणों को कवर करना चाहता है)।

4.2 के बाद से, प्रोग्राम ऑब्जेक्ट्स बनाए जा सकते हैं जिनमें केवल एक shader स्टेज होता है। यह विधि सभी शेडर चरणों को एक कार्यक्रम में जोड़ती है।

शेडर ऑब्जेक्ट संकलन

#include <string>
#include <fstream>

//In C++17, we could take a `std::filesystem::path` instead of a std::string
//for the filename.
GLuint CreateShaderObject(GLenum stage, const std::string &filename)
{
    std::ifstream input(filename.c_str(), std::ios::in | std::ios::binary | std::ios::ate);
    
    //Figure out how big the file is.
    auto fileSize = input.tellg();
    input.seekg(0, ios::beg);
    
    //Read the whole file.
    std::string fileData(fileSize);
    input.read(&fileData[0], fileSize);
    input.close();
    
    //Create a shader name
    auto shader = glCreateShader(stage);

    //Send the shader source code to GL
    auto fileCstr = (const GLchar *)fileData.c_str();
    glShaderSource(shader, 1, &fileCstr, nullptr);

    //Compile the shader
    glCompileShader(shader);

    GLint isCompiled = 0;
    glGetShaderiv(shader, GL_COMPILE_STATUS, &isCompiled);
    if(isCompiled == GL_FALSE)
    {
        GLint maxLength = 0;
        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &maxLength);

        //C++11 does not permit you to overwrite the NUL terminator,
        //even if you are overwriting it with the NUL terminator.
        //C++17 does, so you could subtract 1 from the length and skip the `pop_back`.
        std::basic_string<GLchar> infoLog(maxLength);
        glGetShaderInfoLog(shader, maxLength, &maxLength, &infoLog[0]);
        infoLog.pop_back();

        //We don't need the shader anymore.
        glDeleteShader(shader);

        //Use the infoLog as you see fit.
        
        //Exit with failure.
        return 0;
    }

    return shader;
}

प्रोग्राम ऑब्जेक्ट लिंकिंग

#include <string>

GLuint LinkProgramObject(vector<GLuint> shaders)
{
    //Get a program object.
    auto program = glCreateProgram();

    //Attach our shaders to our program
    for(auto shader : shaders)
        glAttachShader(program, shader);

    //Link our program
    glLinkProgram(program);

    //Note the different functions here: glGetProgram* instead of glGetShader*.
    GLint isLinked = 0;
    glGetProgramiv(program, GL_LINK_STATUS, (int *)&isLinked);
    if(isLinked == GL_FALSE)
    {
        GLint maxLength = 0;
        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &maxLength);

        //C++11 does not permit you to overwrite the NUL terminator,
        //even if you are overwriting it with the NUL terminator.
        //C++17 does, so you could subtract 1 from the length and skip the `pop_back`.
        std::basic_string<GLchar> infoLog(maxLength);
        glGetProgramInfoLog(program, maxLength, &maxLength, &infoLog[0]);
        infoLog.pop_back();
        
        //We don't need the program anymore.
        glDeleteProgram(program);

        //Use the infoLog as you see fit.
        
        //Exit with failure
        return 0;
    }

    //Always detach shaders after a successful link.
    for(auto shader : shaders)
        gldetachShader(program, shader);
        
    return program;
}