OpenGL——圆公式相关变化的绘制

#include<iostream>
#include <math.h>
//旧版本 固定管线
#include<Windows.h>
#include <GL/glut.h>

using namespace std;

const GLdouble twoPi = 6.283185;

struct screenPt {
    GLint x, y;
};

typedef enum{ limacon =1, cardioid, threeLeaf, fourLeaf, spiral} curveName;


GLsizei winWidth = 600, winHeight = 500;


void init()
{
    //窗口背景为白色
    glClearColor(1, 1, 1, 1);
    glMatrixMode(GL_PROJECTION);
    gluOrtho2D(0.0, 200.0, 0.0, 150.0);
}

void lineSegment(screenPt pt1, screenPt pt2)
{
    glBegin(GL_LINES);
    glVertex2i(pt1.x, pt1.y);
    glVertex2i(pt2.x, pt2.y);
    glEnd();
}

void drawCurve(GLint curveNum)
{
    const GLdouble twoPi = 6.283185;
    const GLint a = 175, b = 60;

    GLfloat r, theta, dtheta = 1.0 / float(a);
    GLint x0 = 200, y0 = 250;
    screenPt curvePt[2];

    glColor3f(0.0, 0.0, 0.0);
    curvePt[0].x = x0;
    curvePt[0].y = y0;


    switch (curveNum) {
    case limacon:
        curvePt[0].x += a + b;
        break;
    case cardioid:
        curvePt[0].x += a + a;
        break;
    case threeLeaf:
        curvePt[0].x += a;
        break;
    case fourLeaf:
        curvePt[0].x += a;
        break;
    case spiral:
        break;
    default:
        break;
    }

    theta = dtheta;

    while (theta < twoPi) {
        switch (curveNum) {
        case limacon:
            r = a * cos(theta) + b;
            break;
        case cardioid:
            r = a * (1 + cos(theta));
            break;
        case threeLeaf:
            r = a * cos(theta * 3);
            break;
        case fourLeaf:
            r = a * cos(theta * 2);
            break;
        case spiral:
            r = (a / 4.0) * theta;
            break;
        default:
            break;
        }
        curvePt[1].x = x0 + r * cos(theta);
        curvePt[1].y = y0 + r * sin(theta);
        lineSegment(curvePt[0], curvePt[1]);
        
        curvePt[0].x = curvePt[1].x;
        curvePt[0].y = curvePt[1].y;
        theta += dtheta;
    }
}


void displayFcn()
{    
    GLint curveNum;

    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(0.0, 0.0, 1.0);
    cout << "选择下列任意图形进行绘制\n";
    cout << "1-limacon, 2-cardioid, 3-threeLeaf, 4-fourLeaf, 5-spiral\n";
    
    if (curveNum == 1 || curveNum == 2 || curveNum == 3 || curveNum == 4 || curveNum == 5) {
        drawCurve(curveNum);
    }
    else {
        exit(0);
    }
        glFlush();
    
}

void winReshapeFcn(GLint newWidth, GLint newHeight)
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, GLdouble(newWidth), 0.0, GLdouble(newHeight));
    glClear(GL_COLOR_BUFFER_BIT);

    winWidth = newWidth;
    winHeight = newHeight;
}

int main(int argc, char* argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(winWidth, winHeight);
    glutCreateWindow("Curves");
    init();
   
    glutDisplayFunc(displayFcn);
    glutReshapeFunc(winReshapeFcn);
    glutMainLoop();

    system("pause");
    return 0;


}