需要帮助这个opengl程序 [英] Need help with this opengl program

问题描述

我可以理解这个功能，但是无法理解它在这个步骤中是如何工作的。



我是什么尝试过：

i can understand the function but cant understand how it work with this steps in c
++

What I have tried:

#include <windows.h>   // use as needed for your system
#include <gl/Gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#define ORTHO_SCALE 10.

GLfloat triangle_vertices[] = {
    -0.5, 0.0,
     0.5, 0.0,
     0.0, 1.0
};

struct {
    struct {
        struct {
            GLfloat x, y;
        } pos;
        GLfloat rot;
    } triangle;
} sceneinfo;

void display(void);
void keyboard(unsigned char key, int x, int y);
void special(int key, int x, int y);

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);

    glutCreateWindow("simple triangle test");
    glutDisplayFunc(display);
    glutKeyboardFunc(keyboard);
    glutSpecialFunc(special);

    glutMainLoop();

    return 0;
}

void display(void)
{
    GLuint win_width, win_height;
    GLfloat win_aspect;

    win_width  = glutGet(GLUT_WINDOW_WIDTH);
    win_height = glutGet(GLUT_WINDOW_HEIGHT);
    win_aspect = (float)win_width/(float)win_height;

    glViewport(0, 0, win_width, win_height);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-win_aspect * ORTHO_SCALE, 
             win_aspect * ORTHO_SCALE, 
        -ORTHO_SCALE, 
         ORTHO_SCALE,
         -1., 1.);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glPushMatrix();

    glTranslatef(sceneinfo.triangle.pos.x, sceneinfo.triangle.pos.y, 0.);
    glRotatef(sceneinfo.triangle.rot, 0, 0, 1.);

    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(2, GL_FLOAT, 0, triangle_vertices);
    glDrawArrays(GL_TRIANGLES, 0, 3);

    glPopMatrix();

    glutSwapBuffers();
}

void keyboard(unsigned char key, int x, int y)
{
    switch(key) {
    case '+':
        sceneinfo.triangle.rot += 2.;
        break;
    case '-':
        sceneinfo.triangle.rot -= 2.;
        break;
    }
    glutPostRedisplay();
}

void special(int key, int x, int y)
{
    switch(key) {
    case GLUT_KEY_LEFT:
        sceneinfo.triangle.pos.x -= 0.2;
        break;
    case GLUT_KEY_RIGHT:
        sceneinfo.triangle.pos.x += 0.2;
        break;
    case GLUT_KEY_UP:
        sceneinfo.triangle.pos.y += 0.2;
        break;
    case GLUT_KEY_DOWN:
        sceneinfo.triangle.pos.y -= 0.2;
        break;
    }
    glutPostRedisplay();
}

推荐答案

当你不明白你的代码在做什么或为什么它做它做的时候，答案就是答案是调试器。

使用调试器查看代码正在执行的操作。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量，这是一个令人难以置信的学习工具。



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调试器在这里向您展示您的代码在做什么你的任务是与它应该做的事情进行比较。

调试器中没有魔法，它没有发现错误，它只是帮助你。当代码没有达到预期的效果时，你就会接近一个错误。

When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute, it is an incredible learning tool.

Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

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