两点三次Hermiter插值C++代码

#include <math.h>
#include <gl/glut.h>
#include <iostream>
using namespace std;

struct  Point2
{
    double x;
    double y;

    Point2(int px, int py) { x = px; y = py; }
};

Point2 P0(100, 200);
Point2 P1(350, 200);
Point2 derP0(200, 200);
Point2 derP1(200, 200);

bool mouseLeftDown = false;
bool mouseRightDown = false;

/*计算Hermite曲线*/
void Hermit(int n)
{
    float f1, f2, f3, f4;

    double deltaT = 1.0 / n;

    glBegin(GL_LINE_STRIP);
    for (int i = 0; i <= n; i++) {

        double T = i * deltaT;

        f1 = 2.0*pow(T, 3) - 3.0*pow(T, 2) + 1.0;
        f2 = -2.0*pow(T, 3) + 3.0*pow(T, 2);
        f3 = pow(T, 3) - 2.0*pow(T, 2) + T;
        f4 = pow(T, 3) - pow(T, 2);

        glVertex2f(f1*P0.x + f2*P1.x + f3*derP0.x + f4*derP1.x,
            f1*P0.y + f2*P1.y + f3*derP0.y + f4*derP1.y);
    }
    glEnd();
}

/*用鼠标进行绘制，完成后可改变控制点，拖动即可*/
void display() {
    glClear(GL_COLOR_BUFFER_BIT);

    glLineWidth(1.5);
    glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_LINES);
    glVertex2f(P0.x, P0.y);
    glVertex2f(P0.x + derP0.x / 4, P0.y + derP0.y / 4);
    glVertex2f(P1.x, P1.y);
    glVertex2f(P1.x - derP1.x / 4, P1.y - derP1.y / 4);
    glEnd();

    glColor3f(0.0, 0.0, 1.0);
    glPointSize(10.0f);

    glBegin(GL_POINTS);
    glVertex2f(P0.x, P0.y);
    glVertex2f(P0.x + derP0.x / 4, P0.y + derP0.y / 4);
    glVertex2f(P1.x, P1.y);
    glVertex2f(P1.x - derP1.x / 4, P1.y - derP1.y / 4);
    glEnd();

    Hermit(20);

    glFlush();
    glutSwapBuffers();
}

void init()
{
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glShadeModel(GL_FLAT);
}

void myReshape(int w, int h)
{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLsizei)w, (GLsizei)h, 0.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void mouse(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        mouseLeftDown = true;
    }

    if (button == GLUT_LEFT_BUTTON && state == GLUT_UP)
    {
        mouseLeftDown = false;
    }

    if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
    {
        mouseRightDown = true;
    }

    if (button == GLUT_RIGHT_BUTTON && state == GLUT_UP)
    {
        mouseRightDown = false;
    }
}

double distance(int x1, int y1, int x2, int y2)
{
    return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

void motion(int x, int y)
{
    if (mouseLeftDown)
    {
        if (distance(P0.x + derP0.x / 4, P0.y + derP0.y / 4, x, y) < 20)
        {
            derP0.x = (x - P0.x) * 4;
            derP0.y = (y - P0.y) * 4;
        }

        if (distance(P1.x - derP1.x / 4, P1.y - derP1.y / 4, x, y) < 20)
        {
            derP1.x = (P1.x - x) * 4;
            derP1.y = (P1.y - y) * 4;
        }
    }

    glutPostRedisplay();
}

int  main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(450, 450);
    glutInitWindowPosition(200, 200);
    glutCreateWindow("hello");
    init();

    glutDisplayFunc(display);
    glutReshapeFunc(myReshape);
    glutMouseFunc(mouse);
    glutMotionFunc(motion);

    glutMainLoop();
    return 0;
}