OpenGL手动绘制线框球体和棱锥

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此代码还不完善，画球体和正棱锥封装不完善，封装成任一点为中心画更好。

实现了三个要求：

  1. 将绘制圆的过程做成一个显示列表，并调用显示列表显示一个圆。
  2. 绘制一个正棱锥。（本题不能用GLUT中的对象来绘制）
  3. 绘制一个球。（同上）

其中第一个要求在实现下面功能是并没有用，只是为了实现要求，因为虽然显示列表保存后能提高性能，但保存后不能修改，所以下面没用到。

画棱锥了球时半径的变化用相似算的。

代码

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#include <windows.h>
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
#include <bits/stdc++.h>
using namespace std;
#include <stdlib.h>
const double PI = acos(-1.0);

static GLsizei iMode = 1;
static GLfloat xRot = 0;
static GLfloat yRot = 0;

GLint n = 5;
GLint Circle_List = 0;

void Initial(){
    glClearColor(1, 1, 1, 1);
    glColor3f(0, 0, 0);
}

void ChangeSize(int w, int h){
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-1.5, 1.5, -1.5, 1.5);
}

void Draw_Circle(int n, double r, double z){
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    glBegin(GL_POLYGON);
        for(int i=0; i<n; i++){
            glVertex3f(r*cos(2*i*PI/n), r*sin(2*i*PI/n), z);
        }
    glEnd();
}

GLint GenCircleList(){
    GLint lid = glGenLists(1);
    glNewList(lid, GL_COMPILE);
        Draw_Circle(360, 0.5, 0);
    glEndList();
    return lid;
}
void Draw_C(){
    glPushMatrix();
        glCallList(Circle_List);
    glPopMatrix();
}
void Draw_Cylinder(int n=5, double r=0.5, double h=1, int layer = 10){
    glPushMatrix();
        for(int i=0; i<n; i++){ // 棱
            glBegin(GL_LINES);
                glVertex3f(0, 0, h);
                glVertex3f(r*cos(2*i*PI/n), r*sin(2*i*PI/n), 0);
            glEnd();
        }

        for(double i=0; i<h; i+=h/layer){ // 多边形框
            double new_r = r*(h-i)/h;
            Draw_Circle(n, new_r, i);
        }
    glPopMatrix();
}
void Draw_Line_Sphere(int n=360, double r=1, int layer=5, int line=10){
    glPushMatrix();
        for(double i=0; i<=r; i+=r/layer){ // 圆框
            double new_r = sqrt(r*r-i*i);
            Draw_Circle(n, new_r, i);
            Draw_Circle(n, new_r, -i);
        }
        glRotatef(90, 0, 1, 0);
        for(double i=0; i<360; i+=360.0/line){
            glRotated(360.0/line, 1, 0, 0);
            Draw_Circle(n, r, 0);
        }
    glPopMatrix();
}
void Display(){
    glClear(GL_COLOR_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glRotatef(xRot, 1, 0, 0);
    glRotatef(yRot, 0, 1, 0);

    switch(iMode){
    case 1: Draw_C();  break;
    case 2: Draw_Cylinder(n); break;
    case 3: Draw_Line_Sphere(); break;
    }

    glFlush();
}

void SpecialKeys(int key, int x, int y){
    if(key == GLUT_KEY_UP) xRot -= 5;
    if(key == GLUT_KEY_DOWN) xRot += 5;
    if(key == GLUT_KEY_LEFT) yRot -= 5;
    if(key == GLUT_KEY_RIGHT) yRot += 5;
    if(xRot > 356) xRot = 0;
    if(xRot < -1) xRot = 355;
    if(yRot > 356) yRot = 0;
    if(yRot < -1) yRot = 355;
    glutPostRedisplay();
}
static void key(unsigned char key, int x, int y){
    switch(key){
        case '=': n=min(99, n+1); break;
        case '-': n=max(3, n-1); break;
    }
    glutPostRedisplay();
}

void ProcessMenu(int value){
    iMode = value;
    glutPostRedisplay();
}

int main(int argc, char** argv){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(400, 400);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("Hello");

    int nMainMenu = glutCreateMenu(ProcessMenu);
    glutAddMenuEntry("圆", 1);
    glutAddMenuEntry("线框多棱锥", 2);
    glutAddMenuEntry("线框球体", 3);
    glutAttachMenu(GLUT_RIGHT_BUTTON);


    glutDisplayFunc(Display);
    glutReshapeFunc(ChangeSize);
    glutSpecialFunc(SpecialKeys);
    glutKeyboardFunc(key);
    Initial();

    Circle_List = GenCircleList();

    glutMainLoop();
}
# 使用单$作为行内数学公式分界符