c++ - SFML + OpenGL : Unable to draw cube

Question

我以前使用过 OpenGL，已经有一段时间了，但我不认为它会这么糟糕。这段代码中缺少一些东西。我只是想看看我正在使用 cube() 函数绘制的立方体。

我做过/尝试过的事情...

• 在主循环中翻转 + 和 - z 之间的翻译
• 在主循环之前打开/关闭背面剔除
• glLoadIdentity() 开头
• 在开始时设置我的投影
• 以window.resetGLStates()开头
• window.setActive(true) 开头
• 确保我留在 glMatrixMode(GL_MODELVIEW)

我错过了什么？我只能看到我指定的清晰颜色，填满屏幕并 mock 我。

#include <SFML/System.hpp>
#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/OpenGL.hpp>

void cube();

int gltest()
{
    sf::RenderWindow window(sf::VideoMode(800, 600), "SFML works!", sf::Style::Default);
    window.setVerticalSyncEnabled(true);
    window.setActive(true);
    window.resetGLStates();
    sf::Vector2u wsize = window.getSize();

    glClearColor(0.3f, 0.3f, 0.3f, 1.f);
    glDepthMask(true);
    glEnable(GL_DEPTH_TEST);
    //to make sure I'm not missing anything here.
    glDisable(GL_CULL_FACE);

    glMatrixMode(GL_PROJECTION);
    glViewport(0, 0, wsize.x, wsize.y);
    gluPerspective(60, (float)wsize.x / (float)wsize.y, 0.1f, 512.f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    bool running = true;
    while(running)
    {
        sf::Event event;
        while(window.pollEvent(event))
        {
            switch(event.type)
            {
                case sf::Event::KeyPressed:
                    if(event.key.code != sf::Keyboard::Escape) { break; }
                case sf::Event::Closed:
                    running = false;
                    break;
                case sf::Event::Resized:
                    wsize.x = event.size.width;
                    wsize.y = event.size.height;
                    glMatrixMode(GL_PROJECTION);
                    glViewport(0, 0, wsize.x, wsize.y);
                    gluPerspective(60.f, (float)wsize.x / (float)wsize.y, 0.1f, 512.f);
                    glMatrixMode(GL_MODELVIEW);
                    break;
                default:
                    break;
            }
        }

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

            glPushMatrix();
            glTranslatef(0.f, 0.f, 5.f);

                cube();

            glPopMatrix();

        window.display();
    }

    return 0;
}

void cube()
{
glBegin(GL_QUADS);      // Draw The Cube Using quads
    glColor3f(0.0f,1.0f,0.0f);  // Color Green
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f( 1.0f, 1.0f,-1.0f);  // Top Right Of The Quad (Top)
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f(-1.0f, 1.0f,-1.0f);  // Top Left Of The Quad (Top)
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f(-1.0f, 1.0f, 1.0f);  // Bottom Left Of The Quad (Top)
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f( 1.0f, 1.0f, 1.0f);  // Bottom Right Of The Quad (Top)
    glColor3f(1.0f,0.5f,0.0f);  // Color Orange
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f( 1.0f,-1.0f, 1.0f);  // Top Right Of The Quad (Bottom)
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f(-1.0f,-1.0f, 1.0f);  // Top Left Of The Quad (Bottom)
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f(-1.0f,-1.0f,-1.0f);  // Bottom Left Of The Quad (Bottom)
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f( 1.0f,-1.0f,-1.0f);  // Bottom Right Of The Quad (Bottom)
    glColor3f(1.0f, 0.0f, 0.0f);    // Color Red
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f( 1.0f, 1.0f, 1.0f);  // Top Right Of The Quad (Front)
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f(-1.0f, 1.0f, 1.0f);  // Top Left Of The Quad (Front)
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f(-1.0f,-1.0f, 1.0f);  // Bottom Left Of The Quad (Front)
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f( 1.0f,-1.0f, 1.0f);  // Bottom Right Of The Quad (Front)
    glColor3f(1.0f, 1.0f, 0.0f);    // Color Yellow
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f( 1.0f,-1.0f,-1.0f);  // Top Right Of The Quad (Back)
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f(-1.0f,-1.0f,-1.0f);  // Top Left Of The Quad (Back)
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f(-1.0f, 1.0f,-1.0f);  // Bottom Left Of The Quad (Back)
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f( 1.0f, 1.0f,-1.0f);  // Bottom Right Of The Quad (Back)
    glColor3f(0.0f, 0.0f, 1.0f);    // Color Blue
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f, 1.0f, 1.0f);  // Top Right Of The Quad (Left)
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f, 1.0f,-1.0f);  // Top Left Of The Quad (Left)
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f,-1.0f,-1.0f);  // Bottom Left Of The Quad (Left)
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f,-1.0f, 1.0f);  // Bottom Right Of The Quad (Left)
    glColor3f(1.0f, 0.0f, 1.0f);    // Color Violet
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f, 1.0f,-1.0f);  // Top Right Of The Quad (Right)
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f, 1.0f, 1.0f);  // Top Left Of The Quad (Right)
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f,-1.0f, 1.0f);  // Bottom Left Of The Quad (Right)
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f,-1.0f,-1.0f);  // Bottom Right Of The Quad (Right)
  glEnd();          // End Drawing The Cube
}

Answer 1

这里:

glMatrixMode(GL_PROJECTION);
glViewport(0, 0, wsize.x, wsize.y);
gluPerspective(60, (float)wsize.x / (float)wsize.y, 0.1f, 512.f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

这里:

wsize.x = event.size.width;
wsize.y = event.size.height;
glMatrixMode(GL_PROJECTION);
glViewport(0, 0, wsize.x, wsize.y);
gluPerspective(60.f, (float)wsize.x / (float)wsize.y, 0.1f, 512.f);
glMatrixMode(GL_MODELVIEW);

在 glMatrixMode(GL_PROJECTION) 和 glMatrixMode(GL_MODELVIEW) 调用之后添加一个 glLoadIdentity()。

gluPerspective() 将一个矩阵与当前矩阵相乘。代码似乎假设它覆盖当前矩阵。

gluPerspective() 矩阵乘以自身多次不是有意义的投影矩阵。

当你在那里时，你可以删除调整大小的处理程序:

#include <SFML/System.hpp>
#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <SFML/OpenGL.hpp>

void cube()
{
    glBegin(GL_QUADS);      // Draw The Cube Using quads

    glColor3f(0.0f,1.0f,0.0f);  // Color Green
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f( 1.0f, 1.0f,-1.0f);  // Top Right Of The Quad (Top)
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f(-1.0f, 1.0f,-1.0f);  // Top Left Of The Quad (Top)
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f(-1.0f, 1.0f, 1.0f);  // Bottom Left Of The Quad (Top)
    glNormal3f(0.f, 1.f, 0.f);
    glVertex3f( 1.0f, 1.0f, 1.0f);  // Bottom Right Of The Quad (Top)

    glColor3f(1.0f,0.5f,0.0f);  // Color Orange
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f( 1.0f,-1.0f, 1.0f);  // Top Right Of The Quad (Bottom)
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f(-1.0f,-1.0f, 1.0f);  // Top Left Of The Quad (Bottom)
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f(-1.0f,-1.0f,-1.0f);  // Bottom Left Of The Quad (Bottom)
    glNormal3f(0.f, -1.f, 0.f);
    glVertex3f( 1.0f,-1.0f,-1.0f);  // Bottom Right Of The Quad (Bottom)

    glColor3f(1.0f, 0.0f, 0.0f);    // Color Red
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f( 1.0f, 1.0f, 1.0f);  // Top Right Of The Quad (Front)
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f(-1.0f, 1.0f, 1.0f);  // Top Left Of The Quad (Front)
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f(-1.0f,-1.0f, 1.0f);  // Bottom Left Of The Quad (Front)
    glNormal3f(0.f, 0.f, 1.f);
    glVertex3f( 1.0f,-1.0f, 1.0f);  // Bottom Right Of The Quad (Front)

    glColor3f(1.0f, 1.0f, 0.0f);    // Color Yellow
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f( 1.0f,-1.0f,-1.0f);  // Top Right Of The Quad (Back)
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f(-1.0f,-1.0f,-1.0f);  // Top Left Of The Quad (Back)
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f(-1.0f, 1.0f,-1.0f);  // Bottom Left Of The Quad (Back)
    glNormal3f(0.f, 0.f, -1.f);
    glVertex3f( 1.0f, 1.0f,-1.0f);  // Bottom Right Of The Quad (Back)

    glColor3f(0.0f, 0.0f, 1.0f);    // Color Blue
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f, 1.0f, 1.0f);  // Top Right Of The Quad (Left)
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f, 1.0f,-1.0f);  // Top Left Of The Quad (Left)
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f,-1.0f,-1.0f);  // Bottom Left Of The Quad (Left)
    glNormal3f(-1.f, 0.f, 0.f);
    glVertex3f(-1.0f,-1.0f, 1.0f);  // Bottom Right Of The Quad (Left)

    glColor3f(1.0f, 0.0f, 1.0f);    // Color Violet
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f, 1.0f,-1.0f);  // Top Right Of The Quad (Right)
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f, 1.0f, 1.0f);  // Top Left Of The Quad (Right)
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f,-1.0f, 1.0f);  // Bottom Left Of The Quad (Right)
    glNormal3f(1.f, 0.f, 0.f);
    glVertex3f( 1.0f,-1.0f,-1.0f);  // Bottom Right Of The Quad (Right)

    glEnd();          // End Drawing The Cube
}

int main()
{
    sf::RenderWindow window(sf::VideoMode(800, 600), "SFML works!", sf::Style::Default);
    window.setVerticalSyncEnabled(true);
    window.setActive(true);
    window.resetGLStates();

    bool running = true;
    while(running)
    {
        sf::Event event;
        while(window.pollEvent(event))
        {
            switch(event.type)
            {
            case sf::Event::KeyPressed:
                if(event.key.code != sf::Keyboard::Escape) { break; }
            case sf::Event::Closed:
                running = false;
                break;
            default:
                break;
            }
        }

        glClearColor(0.3f, 0.3f, 0.3f, 1.f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        sf::Vector2u wsize = window.getSize();
        glViewport(0, 0, wsize.x, wsize.y);
        gluPerspective(60, (float)wsize.x / (float)wsize.y, 0.1f, 512.f);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glPushMatrix();
        glTranslatef(0.f, 0.f, -5.f);

        cube();

        glPopMatrix();

        GLenum err = glGetError();

        window.display();
    }

    return 0;
}