glsl 的 GPGPU 教程

GLSL是OpenGL着色器语言，可以用于编写GPU计算程序，也就是GPGPU。以下是一个简单的GLSL GPGPU程序示例。

首先，我们需要一个着色器程序，它将执行我们的计算。以下是一个使用GLSL的简单计算着色器程序示例：

#version 330

layout (local_size_x = 16, local_size_y = 16) in;

layout (rgba32f, binding = 0) uniform image2D inputImage;
layout (rgba32f, binding = 1) uniform image2D outputImage;

void main() {
    ivec2 storePos = ivec2(gl_GlobalInvocationID.xy);
    vec4 data = imageLoad(inputImage, storePos);

    // perform computation on data

    imageStore(outputImage, storePos, data);
}

这个着色器程序将从输入图像中读取像素数据并执行计算，然后将计算结果写回到输出图像中。

接下来，我们需要在主程序中设置输入和输出图像以及调用着色器程序。以下是一个示例程序：

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#include <iostream>
#include <vector>

const int WIDTH = 512;
const int HEIGHT = 512;

int main() {
    if (!glfwInit()) {
        std::cerr << "Failed to initialize GLFW." << std::endl;
        return -1;
    }

    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 5);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "GLSL GPGPU Tutorial", nullptr, nullptr);
    if (!window) {
        std::cerr << "Failed to create GLFW window." << std::endl;
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    glewExperimental = true;
    if (glewInit() != GLEW_OK) {
        std::cerr << "Failed to initialize GLEW." << std::endl;
        glfwTerminate();
        return -1;
    }

    GLuint inputImage, outputImage;
    glGenTextures(1, &inputImage);
    glBindTexture(GL_TEXTURE_2D, inputImage);
    glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA32F, WIDTH, HEIGHT);

    glGenTextures(1, &outputImage);
    glBindTexture(GL_TEXTURE_2D, outputImage);
    glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA32F, WIDTH, HEIGHT);

    GLuint shader = glCreateShader(GL_COMPUTE_SHADER);
    const char* shaderSource =
        "#version 330\n"
        "layout (local_size_x = 16, local_size_y = 16) in;\n"
        "layout (rgba32f, binding = 0) uniform image2D inputImage;\n"
        "layout (rgba32f, binding = 1) uniform image2D outputImage;\n"
        "void main() {\n"
        "    ivec2 storePos = ivec2(gl_GlobalInvocationID.xy);\n"
        "    vec4 data = imageLoad(inputImage, storePos);\n"
        "    // perform computation on data\n"
        "    imageStore(outputImage, storePos, data);\n"
        "}";
    glShaderSource(shader, 1, &shaderSource, nullptr);
    glCompileShader(shader);

    GLuint program = glCreateProgram();
    glAttachShader(program, shader);
    glLinkProgram(program);

    glUseProgram(program);
    glBindImageTexture(0, inputImage, 0, GL_FALSE, 0, GL_READ_ONLY, GL_RGBA32F);
    glBindImageTexture(1, outputImage, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA32F);

    glDispatchCompute(WIDTH / 16, HEIGHT / 16, 1);
    glMemoryBarrier(GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);

    glfwTerminate();
    return 0;
}

此程序将创建一个窗口，创建两个纹理，一个输入，一个输出，然后在主程序中调用着色器程序，将输入图像传递给着色器程序并从输出图像中读取结果。

以上是一个简单的GLSL GPGPU程序示例，你可以根据自己的需求进行修改和扩展。