基本 OpenGL 渲染的问题？

Question

我是 OpenGL 的完全初学者，只是想学习（暂时从 freeglut 开始）。到目前为止，我有以下代码应该绘制一些基本的 3D 对象。问题是无论我在渲染函数中放入什么（尽管它确实执行了），它都只显示一个空白窗口。

#include "stdafx.h"
#include <iostream>
#include "dependente\glew\glew.h"
#include "dependente\freeglut\glut.h"

void render()
{
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glEnable(GL_DEPTH_TEST);

    glTranslatef(-1.5f, 1.0f, -6.0f);                                     // Translate back and to the left

    glPushMatrix();                                                         // Push the current modelview matrix on the matrix                         // Rotate on all 3 axis
    glBegin(GL_TRIANGLES);                                                // Draw a pyramid
    glColor3f(1.0f, 0.0f, 0.0f);                                      // Red
    glVertex3f(0.0f, 1.0f, 0.0f);                                     // Top of front face
    glColor3f(0.0f, 1.0f, 0.0f);                                      // Green
    glVertex3f(-1.0f, -1.0f, 1.0f);                                   // Left of front face
    glColor3f(0.0f, 0.0f, 1.0f);                                      // Blue
    glVertex3f(1.0f, -1.0f, 1.0f);                                    // Right of front face

    glColor3f(1.0f, 0.0f, 0.0f);                                      // Red
    glVertex3f(0.0f, 1.0f, 0.0f);                                     // Top of right face
    glColor3f(0.0f, 0.0f, 1.0f);                                      // Blue
    glVertex3f(1.0f, -1.0f, 1.0f);                                    // Left of right face
    glColor3f(0.0f, 1.0f, 0.0f);                                      // Green
    glVertex3f(1.0f, -1.0f, -1.0f);                                   // Right of right face

    glColor3f(1.0f, 0.0f, 0.0f);                                      // Red
    glVertex3f(0.0f, 1.0f, 0.0f);                                     // Top of back face
    glColor3f(0.0f, 1.0f, 0.0f);                                      // Green
    glVertex3f(1.0f, -1.0f, -1.0f);                                   // Left of back face
    glColor3f(0.0f, 0.0f, 1.0f);                                      // Blue
    glVertex3f(-1.0f, -1.0f, -1.0f);                                  // Right of back face

    glColor3f(1.0f, 0.0f, 0.0f);                                      // Red
    glVertex3f(0.0f, 1.0f, 0.0f);                                     // Top of left face
    glColor3f(0.0f, 0.0f, 1.0f);                                      // Blue
    glVertex3f(-1.0f, -1.0f, -1.0f);                                  // Left of left face
    glColor3f(0.0f, 1.0f, 0.0f);                                      // Green
    glVertex3f(-1.0f, -1.0f, 1.0f);                                   // Right of left face
    glEnd();

    // Render a quad for the bottom of our pyramid
    glBegin(GL_QUADS);
    glColor3f(0.0f, 1.0f, 0.0f);                                      // Green
    glVertex3f(-1.0f, -1.0f, 1.0f);                                   // Left/right of front/left face
    glColor3f(0.0f, 0.0f, 1.0f);                                      // Blue
    glVertex3f(1.0f, -1.0f, 1.0f);                                    // Right/left of front/right face
    glColor3f(0.0f, 1.0f, 0.0f);                                      // Green
    glVertex3f(1.0f, -1.0f, -1.0f);                                   // Right/left of right/back face
    glColor3f(0.0f, 0.0f, 1.0f);                                      // Blue
    glVertex3f(-1.0f, -1.0f, -1.0f);                                  // Left/right of right/back face
    glEnd();
    glPopMatrix();

    glTranslatef(3.0f, 0.0f, 0.0f);                                        // Translate right
    glPushMatrix();                                                         // Push the current modelview matrix on the matrix stack                         // Rotate the primitive on all 3 axis
    glBegin(GL_QUADS);
    // Top face
    glColor3f(0.0f, 1.0f, 0.0f);                                   // Green
    glVertex3f(1.0f, 1.0f, -1.0f);                                   // Top-right of top face
    glVertex3f(-1.0f, 1.0f, -1.0f);                                   // Top-left of top face
    glVertex3f(-1.0f, 1.0f, 1.0f);                                   // Bottom-left of top face
    glVertex3f(1.0f, 1.0f, 1.0f);                                   // Bottom-right of top face

    // Bottom face
    glColor3f(1.0f, 0.5f, 0.0f);                                  // Orange
    glVertex3f(1.0f, -1.0f, -1.0f);                                  // Top-right of bottom face
    glVertex3f(-1.0f, -1.0f, -1.0f);                                  // Top-left of bottom face
    glVertex3f(-1.0f, -1.0f, 1.0f);                                  // Bottom-left of bottom face
    glVertex3f(1.0f, -1.0f, 1.0f);                                  // Bottom-right of bottom face

    // Front face
    glColor3f(1.0f, 0.0f, 0.0f);                                  // Red
    glVertex3f(1.0f, 1.0f, 1.0f);                                  // Top-Right of front face
    glVertex3f(-1.0f, 1.0f, 1.0f);                                  // Top-left of front face
    glVertex3f(-1.0f, -1.0f, 1.0f);                                  // Bottom-left of front face
    glVertex3f(1.0f, -1.0f, 1.0f);                                  // Bottom-right of front face

    // Back face
    glColor3f(1.0f, 1.0f, 0.0f);                                 // Yellow
    glVertex3f(1.0f, -1.0f, -1.0f);                                 // Bottom-Left of back face
    glVertex3f(-1.0f, -1.0f, -1.0f);                                 // Bottom-Right of back face
    glVertex3f(-1.0f, 1.0f, -1.0f);                                 // Top-Right of back face
    glVertex3f(1.0f, 1.0f, -1.0f);                                 // Top-Left of back face

    // Left face
    glColor3f(0.0f, 0.0f, 1.0f);                                   // Blue
    glVertex3f(-1.0f, 1.0f, 1.0f);                                   // Top-Right of left face
    glVertex3f(-1.0f, 1.0f, -1.0f);                                   // Top-Left of left face
    glVertex3f(-1.0f, -1.0f, -1.0f);                                   // Bottom-Left of left face
    glVertex3f(-1.0f, -1.0f, 1.0f);                                   // Bottom-Right of left face

    // Right face
    glColor3f(1.0f, 0.0f, 1.0f);                                   // Violet
    glVertex3f(1.0f, 1.0f, 1.0f);                                   // Top-Right of left face
    glVertex3f(1.0f, 1.0f, -1.0f);                                   // Top-Left of left face
    glVertex3f(1.0f, -1.0f, -1.0f);                                   // Bottom-Left of left face
    glVertex3f(1.0f, -1.0f, 1.0f);                                   // Bottom-Right of left face
    glEnd();
    glPopMatrix();

    glTranslatef(-1.5f, -3.0f, 0.0f);                                     // Back to center and lower screen
    glPushMatrix();
    glColor3f(1.0f, 1.0f, 0.0f);                                          // Yellow
    glutSolidSphere(1.0f, 16, 16);                                        // Use GLUT to draw a solid sphere
    glScalef(1.01f, 1.01f, 1.01f);
    glColor3f(1.0f, 0.0f, 0.0f);                                          // Red
    glutWireSphere(1.0f, 16, 16);                                         // Use GLUT to draw a wireframe sphere
    glPopMatrix();
}

void initGlut(int argc, char* argv[]) {
    std::cout << "Initialise OpenGL..." << std::endl;

    glutInit(&argc, argv);
    int iScreenWidth = glutGet(GLUT_SCREEN_WIDTH);
    int iScreenHeight = glutGet(GLUT_SCREEN_HEIGHT);

    glutInitDisplayMode(GLUT_RGBA | GLUT_ALPHA | GLUT_DOUBLE | GLUT_DEPTH);

    glutInitWindowPosition(120, 120);
    glutInitWindowSize(600, 600);

    glutCreateWindow("OpenGL");

    // Register GLUT callbacks
    glutDisplayFunc(render);

    // Setup initial GL State
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
    glClearDepth(1.0f);

    glShadeModel(GL_SMOOTH);
    glutMainLoop();
    std::cout << "Initialise OpenGL: Success!" << std::endl;
}

int _tmain(int argc, char* argv[])
{
    initGlut(argc, argv);
    return 0;
}

希望有更多经验的人能让我知道我缺少什么明显的东西。

Answer 1

这是我调试“OpenGL 没有绘制任何东西”问题的方法：

1. 将此代码添加到我的render() 函数的开头：glClearColor (1, 1, 0, 1); glClear (GL_COLOR_BUFFER_BIT); 如果输出变为黄色，它正在调用您的render() 函数并正确清除输出。然后，您可以删除该代码或将其注释掉。如果输出没有变黄，那么您的 render() 函数没有被调用，或者它被调用了，但是您的 OpenGL 状态设置为不绘制到屏幕上。 （也许当时是错误的上下文，或者当前 FBO 的颜色附件不是您认为的那样。）

2. 尝试以原点为中心绘制一个没有纹理或着色器的白色三角形。如果它出现，那么您尝试绘制的其他几何图形可能是错误的。如果它没有出现，问题可能是您的矩阵计算（投影或模型视图矩阵）。 （您是否将“相机”指向您认为自己所在的位置？您的对象是否被绘制在您认为的位置？）它也可能是照明、混合或深度测试。为了确定，我将所有这些都关闭以进行此类测试。 （有关如何打开和关闭它们，请参阅glEnable()/glDisable()。）

3. 如果这些东西有效，我开始打开我在上面关闭的东西：纹理、着色器、照明、混合、深度测试。我一次打开一个，直到出现问题。

如果没有出错，那么我的对象的几何形状可能是错误的。