计算机图形学-三次Bezier曲线的绘制

#include <GL/glut.h>

#include <stdio.h>

#include <stdlib.h>

#include <vector>

using namespace std;

struct Point {

int x, y;

};

Point pt[4], bz[11];

vector<Point> vpt;

bool bDraw;

int nInput;

void CalcBZPoints()

{

float a0, a1, a2, a3, b0, b1, b2, b3;

a0 = pt[0].x;

a1 = -3 * pt[0].x + 3 * pt[1].x;

a2 = 3 * pt[0].x - 6 * pt[1].x + 3 * pt[2].x;

a3 = -pt[0].x + 3 * pt[1].x - 3 * pt[2].x + pt[3].x;

b0 = pt[0].y;

b1 = -3 * pt[0].y + 3 * pt[1].y;

b2 = 3 * pt[0].y - 6 * pt[1].y + 3 * pt[2].y;

b3 = -pt[0].y + 3 * pt[1].y - 3 * pt[2].y + pt[3].y;

float t = 0;

float dt = 0.01;

for (int i = 0; t<1.1; t += 0.1, i++)

{

bz[i].x = a0 + a1*t + a2*t*t + a3*t*t*t;

bz[i].y = b0 + b1*t + b2*t*t + b3*t*t*t;

}

}

void ControlPoint(vector<Point> vpt)

{

glPointSize(2);

for (int i = 0; i<vpt.size(); i++)

{

glBegin(GL_POINTS);

glColor3f(1.0f, 0.0f, 0.0f); glVertex2i(vpt[i].x, vpt[i].y);

glEnd();

}

}

void PolylineGL(Point *pt, int num)

{

glBegin(GL_LINE_STRIP);

for (int i = 0; i<num; i++)

{

glVertex2i(pt[i].x, pt[i].y);

}

glEnd();

}

void myDisplay()

{

glClear(GL_COLOR_BUFFER_BIT);

glColor3f(1.0f, 1.0f, 1.0f);

if (vpt.size() > 0) {

ControlPoint(vpt);

}

if (bDraw)

{
glColor3f(1.0f, 1.0f, 0.0f);
PolylineGL(pt, 4);

CalcBZPoints();
glColor3f(0.0f, 1.0f, 1.0f);
PolylineGL(bz, 11);

}

glFlush();

}

void Init()

{

glClearColor(0.0, 0.0, 0.0, 0.0);

glShadeModel(GL_SMOOTH);

printf("Please Click left button of mouse to input control point of Bezier Curve!\n");

}

void Reshape(int w, int h)

{

glViewport(0, 0, (GLsizei)w, (GLsizei)h);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluOrtho2D(0.0, (GLdouble)w, 0.0, (GLdouble)h);

}

void mouse(int button, int state, int x, int y)

{

switch (button)

{

case GLUT_LEFT_BUTTON:

if (state == GLUT_DOWN)

{

if (nInput == 0)

{

pt[0].x = x;

pt[0].y = 480 - y;

nInput = 1;

vpt.clear();

vpt.push_back(pt[0]);

bDraw = false;

glutPostRedisplay();//

}

else if (nInput == 1)

{

pt[1].x = x;

pt[1].y = 480 - y;

vpt.push_back(pt[1]);

nInput = 2;

glutPostRedisplay();//

}

else if (nInput == 2)

{

pt[2].x = x;

pt[2].y = 480 - y;

vpt.push_back(pt[2]);

nInput = 3;

glutPostRedisplay();//

}

else if (nInput == 3)

{

pt[3].x = x;

pt[3].y = 480 - y;

bDraw = true;

vpt.push_back(pt[3]);

nInput = 0;

glutPostRedisplay();//

}

}

break;

default:

break;

}

}

int main(int argc, char *argv[])

{

glutInit(&argc, argv);

glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);

glutInitWindowPosition(100, 100);

glutInitWindowSize(640, 480);

glutCreateWindow("Hello World!");

Init();

glutDisplayFunc(myDisplay);

glutReshapeFunc(Reshape);

glutMouseFunc(mouse);

glutMainLoop();

return 0;

}