OpenGL - Hello三角形未显示

Question

我在这里有我的OpenGL - Hello Triangle演示，但我不能让它工作。有人知道问题出在哪里吗？我能够编译和运行代码，但是三角形没有显示出来。它只打开灰色背景的窗口。

#include <glew/glew.h>
#include <glfw/glfw3.h>
#include <stdio.h>
#include <stdlib.h>

int main() {

    if (!glfwInit()) {
        fprintf(stderr, "Failed to initialize GLFW\n");
        return -1;
    }

    GLFWwindow* window = glfwCreateWindow(800, 800, "Anton Tutorials - Hello Triangle", NULL, NULL);
    if (window == NULL) {
        fprintf(stderr, "Failed to open GLFW window.\n");
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    glewExperimental = GL_TRUE; // Needed in core profile 
    const GLenum err = glewInit();

    if (err != GLEW_OK) {
        fprintf(stderr, "Failed to initialize GLEW\n");
        fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
        return -1;
    }

    // Enable depth-testing
    glEnable(GL_DEPTH_TEST);
    // Depth-testing interprets a smaller value as "closer"
    glDepthFunc(GL_LESS);

    //Defining vertices for triangle                          
    GLfloat points[] = {
        0.0f, 0.5f, 0.0f,
        0.5f, -0.5f, 0.0f,
        -0.5f, -0.5f, 0.0f
    };

    //Vertex buffer object creation
    GLuint vbo = 0;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);

    //Vertex attribute object creation
    GLuint vao = 0;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);
    glDisableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);

    //Loading shaders - Vertex shader
    const char* vertex_shader =
        "#version 410\n"
        "in vec3 vp; "
        "void main() {"
        " gl_Position = vec4 (vp, 1.0);"
        " }";

    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vertex_shader, NULL);
    glCompileShader(vs);

    //Loading shaders - Fragment shader
    const char* fragment_shader =
        "#version 410\n"
        "out vec4 frag_colour; "
        "void main() {"
        " frag_colour = vec4 (0.5, 0.0, 0.5, 1.0);"
        " }";

    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, &fragment_shader, NULL);
    glCompileShader(fs);

    //Attach shaders
    GLuint shader_programme = glCreateProgram();
    glAttachShader(shader_programme, fs);
    glAttachShader(shader_programme, vs);
    glLinkProgram(shader_programme);

    //RenderLoop
    while (!glfwWindowShouldClose(window))
    {
        glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glUseProgram(shader_programme);
        glBindVertexArray(vao);

        glDrawArrays(GL_TRIANGLES, 0, 3);

        glfwPollEvents();
        glfwSwapBuffers(window);
    }

    glfwTerminate();
    return 0;
}

Answer 1

您需要启用'vp‘属性。

在前面的代码中，您可以这样说：

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, NULL);

如果vp着色器变量的布局位置发生更改，则该变量现在可能不再有效。

这样做会更好：

GLint vpAttr = glGetAttribLocation(shader_programme, "vp");
glVertexAttribPointer(vpAttr, 3, GL_FLOAT, GL_FALSE, 0, NULL);

然后启用该属性：

glEnableVertexAttribArray(vpAttr);

否则，应在顶点着色器中显式设置vp的布局位置，以便可以放心地使用0：

"layout (location=0) in vec3 vp;"