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001.#include <math.h>
002.#include <gl/glut.h>
003.#include <iostream>
004.using namespace std;
005.
006.#define NUM_POINTS 6
007.#define NUM_SEGMENTS (NUM_POINTS-3)
008.
009.struct Point2
010.{
011. double x;
012. double y;
013.
014. Point2() { ; }
015. Point2(int px, int py) { x = px; y = py; }
016. void SetPoint2(int px, int py) { x = px; y = py; }
017.};
018.
019./*全局变量*/
020.Point2 vec[NUM_POINTS];
021.bool mouseLeftDown = false;
022.
023./*绘制B样条曲线*/
024.void Bspline(int n)
025.{
026. float f1, f2, f3, f4;
027. float deltaT = 1.0 / n;
028. float T;
029.
030. glBegin(GL_LINE_STRIP);
031. for (int num = 0; num < NUM_SEGMENTS; num++)
032. {
033. for (int i = 0; i <= n; i++) {
034.
035. T = i * deltaT;
036.
037. f1 = (-T*T*T + 3*T*T - 3*T + 1) / 6.0;
038. f2 =(3*T*T*T - 6*T*T + 4) / 6.0;
039. f3 = (-3*T*T*T +3*T*T + 3*T + 1) / 6.0;
040. f4 = (T*T*T) / 6.0;
041.
042. glVertex2f( f1*vec[num].x + f2*vec[num+1].x + f3*vec[num+2].x + f4*vec[num+3].x,
043. f1*vec[num].y + f2*vec[num+1].y + f3*vec[num+2].y + f4*vec[num+3].y);
044. }
045. }
046.
047. glEnd();
048.}
049.
050.
051.void display()
052.{
053. glClear(GL_COLOR_BUFFER_BIT);
054. glLoadIdentity();
055.
056. glLineWidth(1.5f);
057. glColor3f(1.0,0.0,0.0);
058. glBegin(GL_LINE_STRIP);
059. for(int i = 0;i < NUM_POINTS; i++)
060. {
061. glVertex2f(vec[i].x, vec[i].y);
062. }
063. glEnd();
064.
065. glPointSize(10.0f);
066. glColor3f(0.0, 0.0, 1.0);
067. glBegin(GL_POINTS);
068. for(int i = 0;i < NUM_POINTS; i++)
069. {
070. glVertex2f(vec[i].x, vec[i].y);
071. }
072. glEnd();
073.
074. Bspline(20);
075.
076. glFlush();
077. glutSwapBuffers();
078.}
079.
080.void init()
081.{
082. glClearColor(1.0, 1.0, 1.0, 0.0);
083. glShadeModel(GL_FLAT);
084.
085. vec[0].SetPoint2(200, 400);
086. vec[1].SetPoint2(100, 300);
087. vec[2].SetPoint2(200, 200);
088. vec[3].SetPoint2(250, 300);
089. vec[4].SetPoint2(400, 200);
090. vec[5].SetPoint2(400, 400);
091.}
092.
093.void reshape(int w, int h)
094.{
095. glViewport(0, 0, (GLsizei)w, (GLsizei)h);
096. glMatrixMode(GL_PROJECTION);
097. glLoadIdentity();
098. gluOrtho2D(0.0, (GLsizei)w, (GLsizei)h, 0.0);
099. glMatrixMode(GL_MODELVIEW);
100. glLoadIdentity();
101.}
102.
103.void mouse(int button, int state, int x, int y)
104.{
105. if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
106. {
107. mouseLeftDown = true;
108. }
109.
110. if (button == GLUT_LEFT_BUTTON && state == GLUT_UP)
111. {
112. mouseLeftDown = false;
113. }
114.}
115.
116.double distance(int x1, int y1, int x2, int y2)
117.{
118. return sqrt((x1-x2) * (x1 -x2) + (y1-y2) * (y1-y2));
119.}
120.
121.void motion(int x, int y)
122.{
123. if (mouseLeftDown)
124. {
125. for (int i = 0; i < NUM_POINTS; i++)
126. {
127. if (distance(vec[i].x, vec[i].y, x, y) < 20)
128. {
129. vec[i].SetPoint2(x, y);
130. }
131. }
132. }
133.
134. glutPostRedisplay();
135.}
136.
137.int main(int argc,char** argv)
138.{
139. glutInit(&argc,argv);
140. glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE);
141. glutInitWindowSize(500, 500);
142. glutInitWindowPosition (200, 200);
143. glutCreateWindow('B-Spline Curve');
144. init();
145.
146. glutDisplayFunc(display);
147. glutReshapeFunc(reshape);
148. glutMouseFunc(mouse);
149. glutMotionFunc(motion);
150. glutMainLoop();
151.
152. return 0;
153.
154.}
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