从YouTube复制的OpenGl着色器中的语法错误

debugcn 发表于 Dev

吉安·拉格（Gian Laager）

我尝试学习OpenGl，现在我想在黑色背景上制作一个带有顶点和着色器的简单红色三角形。我复制了该YouTube视频中的代码。我改变了看法。那是我的代码：

#include "prec.h"
struct Vector2
{
    float x, y;
};

struct TrianglePos
{
    Vector2 a, b, c;
};

static unsigned int CompileShader(unsigned int type, const std::string& source)
{
    unsigned int id = glCreateShader(type);
    const char* src = source.c_str();
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (!result)
    {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        char* message = (char*)alloca(length * sizeof(char));
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << "Failed to compile shader, message: " << message << std::endl;
        glDeleteShader(id);
        return 0;
    }

    return id;
}

static unsigned int createShader(const std::string& vertexShader, const std::string& fragmentShader)
{
    unsigned int program = glCreateProgram();
    unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
    unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);

    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glValidateProgram(program);

    glDeleteShader(vs);
    glDeleteShader(fs);

    return program;
}

int main() {

    if (!glfwInit())
        return -1;


    GLFWwindow *window = glfwCreateWindow(640, 480, "Sand Box GL", NULL, NULL);

    if (!window) {
        std::cout << "problems with window" << std::endl;
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE;
    if (GLEW_OK != glewInit()) {
        std::cout << "something with glew went wrong" << std::endl;
        return -1;
    }


    TrianglePos trianglePos = {
            -0.5f, -0.5f,
            0.0f, 0.5f,
            0.5f, -0.5f
    };

    unsigned int buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(trianglePos), &trianglePos, GL_STATIC_DRAW);

    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(Vector2), 0);

    std::string vertexShader =
            "#version 400 core\n"
            "\n"
            "layout(location = 0) in vec4 position;\n"
            "\n"
            "void main() \n"
            "{\n"
            "   gl_Position = position;\n"
            "}\n";

    std::string fragmentShader =
            "#version 400 core\n"
            "\n"
            "layout(location = 0) out vec4 color;\n"
            "\n"
            "void main()\n"
            "{\n"
            "   color = vec4(1.0, 0.0, 0.0, 1.0);\n"
            "}\n";

    const char *versionGL;
    versionGL = (char *) (glGetString(GL_VERSION));
    std::cout << "openGl version: " << versionGL << std::endl;

    if(GL_VERSION_4_0)
        std::cout << "opengl 4.0 supported" << std::endl;

    unsigned int shader = createShader(vertexShader, fragmentShader);
    glUseProgram(shader);

    while (!glfwWindowShouldClose(window)) {
        glClear(GL_COLOR_BUFFER_BIT);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        glfwSwapBuffers(window);

        glfwPollEvents();
    }
    glfwTerminate();
    return 0;
}

那就是预编译的头文件（prec.h）：#pragma

#ifndef GLEWINIT_PREC_H
#define GLEWINIT_PREC_H
#endif //GLEWINIT_PREC_H

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

#include <iostream>

程序将其打印到控制台（“支持OpenGL 4.0”表示GL_VERSION_4_0 == true）：

openGl version: 2.1 INTEL-14.5.22 
opengl 4.0 supported

当我尝试运行它时，我从顶点和片段着色器的着色器编译器收到以下错误消息：

ERROR: 0:1: '' :  version '400' is not supported
ERROR: 0:1: '' : syntax error: #version
ERROR: 0:3: 'layout' : syntax error: syntax error

当我将更#version 400 core改为时#version 120，只会得到的语法错误layout。因此，我想我弄乱了一些东西。我可以尝试什么？

拉比德76

您的系统不支持OpenGL 4.0。它仅支持OpenGL 2.1。查看输出

openGl version: 2.1 INTEL-14.5.22

GLSL 1.20对应于OpenGL 2.1。降级着色器：

顶点着色器

#version 120

attribute vec4 position;

void main()
{
    gl_Position = position;
}

片段着色器

#version 120

void main()
{
    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}

分别使用Raw字符串文字（C ++ 11）：

std::string vertexShader =
R"(#version 120

attribute vec4 position;

void main()
{
    gl_Position = position;
}
)";

std::string fragmentShader =
R"(#version 120

void main()
{
    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
)";

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