OpenGL GLFW 简单立方体不渲染

Question

有人

可以告诉我这段代码有什么问题吗，它没有显示带有简单顶点和片段着色器的简单立方体，似乎我已经正确初始化了 gl 和 GLFW，创建了着色器将它们提交并链接，创建了模型视图投影矩阵，并将它们传递给着色器，我不明白为什么它没有渲染。

#include <iostream>
#include <fstream>
#include <GLglew.h>
#include <GLFWglfw3.h>
#include <glmglm.hpp>
#include <glmgtcmatrix_transform.hpp>
#include <glmgtctype_ptr.hpp>
using namespace std;
using namespace glm;
int g_gl_width = 800;
int g_gl_height = 600;
GLFWwindow* g_window = NULL;
void glfw_error_callback(int error, const char* description) {
    cerr << description << endl;
}
void glfw_window_size_callback(GLFWwindow* window, int width, int height) {
    g_gl_width = width;
    g_gl_height = height;
}
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
}
void mouse_button_callback(GLFWwindow* window, int button, int action, int mods)
{
}
int main(int argc, char * argv []){
    glfwSetErrorCallback(glfw_error_callback);
    if (!glfwInit()) {
        cerr << "ERROR: could not start GLFW3n" << endl;
        return false;
    }
    g_window = glfwCreateWindow(
        g_gl_width, g_gl_height, "Extended Init.", NULL, NULL
        );
    if (!g_window) {
        cerr << "ERROR: could not open window with GLFW3n" << endl;
        glfwTerminate();
        return false;
    }
    glfwSetWindowSizeCallback(g_window, glfw_window_size_callback);
    glfwMakeContextCurrent(g_window);
    glfwSetMouseButtonCallback(g_window, mouse_button_callback);
    glfwSetScrollCallback(g_window, scroll_callback);
    glfwWindowHint(GLFW_SAMPLES, 4);
    glewExperimental = GL_TRUE;
    glewInit();
    const GLubyte* renderer = glGetString(GL_RENDERER); 
    const GLubyte* version = glGetString(GL_VERSION);
    cout << "Renderer: " << renderer;
    cout << "OpenGL version supported: " << version;
    glEnable(GL_DEPTH_TEST); // enable depth-testing
    glDepthFunc(GL_LESS); // depth-testing interprets a smaller value as "closer"
    glEnable(GL_CULL_FACE); // cull face
    glCullFace(GL_BACK); // cull back face
    glClearColor(0.2f, 0.2f, 0.2f, 1.0f);
    glViewport(0, 0, g_gl_width, g_gl_height);
    GLfloat points[] = {
        -1.0f, -1.0f, -1.0f, // triangle 1 : begin
        -1.0f, -1.0f, 1.0f,
        -1.0f, 1.0f, 1.0f, // triangle 1 : end
        1.0f, 1.0f, -1.0f, // triangle 2 : begin
        -1.0f, -1.0f, -1.0f,
        -1.0f, 1.0f, -1.0f, // triangle 2 : end
        1.0f, -1.0f, 1.0f,
        -1.0f, -1.0f, -1.0f,
        1.0f, -1.0f, -1.0f,
        1.0f, 1.0f, -1.0f,
        1.0f, -1.0f, -1.0f,
        -1.0f, -1.0f, -1.0f,
        -1.0f, -1.0f, -1.0f,
        -1.0f, 1.0f, 1.0f,
        -1.0f, 1.0f, -1.0f,
        1.0f, -1.0f, 1.0f,
        -1.0f, -1.0f, 1.0f,
        -1.0f, -1.0f, -1.0f,
        -1.0f, 1.0f, 1.0f,
        -1.0f, -1.0f, 1.0f,
        1.0f, -1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,
        1.0f, -1.0f, -1.0f,
        1.0f, 1.0f, -1.0f,
        1.0f, -1.0f, -1.0f,
        1.0f, 1.0f, 1.0f,
        1.0f, -1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, -1.0f,
        -1.0f, 1.0f, -1.0f,
        1.0f, 1.0f, 1.0f,
        -1.0f, 1.0f, -1.0f,
        -1.0f, 1.0f, 1.0f,
        1.0f, 1.0f, 1.0f,
        -1.0f, 1.0f, 1.0f,
        1.0f, -1.0f, 1.0f
    };
    GLuint vao;
    glGenVertexArrays(1, &vao);
    glBindVertexArray(vao);
    GLuint vbo;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(
        GL_ARRAY_BUFFER,
        3 * 36 * sizeof(GLfloat),
        points,
        GL_STATIC_DRAW
        );
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glEnableVertexAttribArray(0);
    const char* vertex_shader =
        "#version 410n"
        "layout(location = 0) in vec3 vertex_position;n"
        "uniform mat4 model, view, projection;n"
        "void main() {n"
        "   gl_Position = projection * view * model * vec4(vertex_position, 1.0);n"
        "}n";
    const char* fragment_shader =
        "#version 410n"
        "void main() {n"
        "   gl_FragColor = vec4(1.0f, 0.0f, 0.0f, 1.0);n"
        "}n";
    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vertex_shader, NULL);
    glCompileShader(vs);
    GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fs, 1, &fragment_shader, NULL);
    glCompileShader(fs);
    GLuint shader_programme = glCreateProgram();
    glAttachShader(shader_programme, fs);
    glAttachShader(shader_programme, vs);
    glLinkProgram(shader_programme);
    mat4 projection = glm::perspective(90.0f, (float)(g_gl_width / g_gl_height), 0.1f, 100.0f);
mat4 view = glm::mat4(1.0f);
view = glm::translate(view, vec3(0.0f, 0.0f, 0.0f));
view = glm::rotate(view, 0.0f, vec3(0.0f, 0.0f, 1.0f));
view = glm::rotate(view, 0.0f, vec3(0.0f, 1.0f, 0.0f));
view = glm::rotate(view, 0.0f, vec3(1.0f, 0.0f, 0.0f));
    mat4 model = glm::mat4(1.0f);
    model = glm::translate(model, vec3(0.0f, 0.0f, 0.0f));
    model = glm::rotate(model, 0.0f, vec3(0.0f, 0.0f, 1.0f));
    model = glm::rotate(model, 0.0f, vec3(0.0f, 1.0f, 0.0f));
    model = glm::rotate(model, 0.0f, vec3(1.0f, 0.0f, 0.0f));
    int model_mat_location = glGetUniformLocation(shader_programme, "model");
    glUniformMatrix4fv(model_mat_location, 1, GL_FALSE, glm::value_ptr(model));
    int view_mat_location = glGetUniformLocation(shader_programme, "view");
    glUniformMatrix4fv(view_mat_location, 1, GL_FALSE, glm::value_ptr(view));
    int proj_mat_location = glGetUniformLocation(shader_programme, "projection");
    glUniformMatrix4fv(proj_mat_location, 1, GL_FALSE, glm::value_ptr(projection));
    glUseProgram(shader_programme);
    while (!glfwWindowShouldClose(g_window)) {
        glfwMakeContextCurrent(g_window);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glViewport(0, 0, g_gl_width, g_gl_height);
        glBindVertexArray(vao);
        glUseProgram(shader_programme);
        glDrawArrays(GL_TRIANGLES, 0, 36);
        if (GLFW_PRESS == glfwGetKey(g_window, GLFW_KEY_ESCAPE)) {
            glfwSetWindowShouldClose(g_window, 1);
        }
        glfwPollEvents();
        glfwSwapBuffers(g_window);
    }
    glfwTerminate();
    return 0;
}

编辑：

我还想指出我在代码中还有另一个错误，其中

mat4 view = glm::mat4(1.0f);
glm::translate(view, vec3(0.0f, 0.0f, 0.0f));
glm::rotate(view, 0.0f, vec3(0.0f, 0.0f, 1.0f));
glm::rotate(view, 0.0f, vec3(0.0f, 1.0f, 0.0f));
glm::rotate(view, 0.0f, vec3(1.0f, 0.0f, 0.0f));

应该是：

mat4 view = glm::mat4(1.0f);
view = glm::translate(view, vec3(0.0f, 0.0f, 0.0f));
view = glm::rotate(view, 0.0f, vec3(0.0f, 0.0f, 1.0f));
view = glm::rotate(view, 0.0f, vec3(0.0f, 1.0f, 0.0f));
view = glm::rotate(view, 0.0f, vec3(1.0f, 0.0f, 0.0f));

和模型也。

Answer 1

问题可能出在这里的代码中。

int model_mat_location = glGetUniformLocation(shader_programme, "model");
glUniformMatrix4fv(model_mat_location, 1, GL_FALSE, glm::value_ptr(model));
int view_mat_location = glGetUniformLocation(shader_programme, "view");
glUniformMatrix4fv(view_mat_location, 1, GL_FALSE, glm::value_ptr(view));
int proj_mat_location = glGetUniformLocation(shader_programme, "projection");
glUniformMatrix4fv(proj_mat_location, 1, GL_FALSE, glm::value_ptr(projection));
glUseProgram(shader_programme);

在尝试对统一值进行任何更改之前，需要调用 glUseProgram。 location变量是为每个着色器独立分配的，这意味着对于程序 1，位置将在 [0,1,2,3,...] 范围内，对于程序 2，位置也将在 [0,1,2,3,...] 范围内。因此，在没有活动程序的情况下调用glUniform*意味着 OpenGL 不知道您要为哪个程序更新制服，因此不知道如何应用您传递的值。

此外，您可能还需要更改此代码：

mat4 view = glm::mat4(1.0f);
glm::translate(view, vec3(0.0f, 0.0f, 0.0f));
glm::rotate(view, 0.0f, vec3(0.0f, 0.0f, 1.0f));
glm::rotate(view, 0.0f, vec3(0.0f, 1.0f, 0.0f));
glm::rotate(view, 0.0f, vec3(1.0f, 0.0f, 0.0f));

虽然这段代码没有根本性的问题，但这会将相机放在立方体内。启用面部剔除后，您可能实际上看不到任何东西，因为所有面部都将背对着您。出于测试目的，请考虑使用 glm::lookAt 。

mat4 view = glm::lookAt(vec3(3, 3, 1), vec3(0, 0, 0), vec3(0, 1, 0));