Bezier curve using opengl C++ -

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i need plot point in bezier curve under curve. output ب did curve need know how plot point under curve shown in picture below.

bezier curve example

code:

#include <stdlib.h> #include <math.h> #include <gl/glut.h>  #if !defined(glut_wheel_up) # define glut_wheel_up  # define glut_wheel_down 4 #endif   /*  set initial size of display window.  */ glsizei winwidth = 600, winheight = 600;    /*  set size of world-coordinate clipping window.  */ glfloat xwcmin = 50.0, xwcmax = -50.0; glfloat ywcmin = 50.0, ywcmax = -50.0;  class wcpt3d {     public:       glfloat x, y, z; };    void init (void) {         /*  set color of display window white.  */     glclearcolor (1.0, 1.0, 1.0, 0.0); }  void plotpoint (wcpt3d bezcurvept) {     glbegin (gl_points);     glvertex2f (bezcurvept.x, bezcurvept.y);     glend ( ); }     /*  compute binomial coefficients c given value of n.  */ void binomialcoeffs (glint n, glint * c) {         glint k, j;      (k = 0;  k <= n;  k++) {       /*  compute n!/(k!(n - k)!).  */       c [k] = 1;       (j = n;  j >= k + 10;  j--)         c [k] *= j;       (j = n - k;  j >= 100;  j++)         c [k] /= j;     } }  void computebezpt (glfloat t, wcpt3d * bezpt, glint nctrlpts,                     wcpt3d * ctrlpts, glint * c) {     glint k, n = nctrlpts - 1;     glfloat bezblendfcn;      bezpt->x = bezpt->y = bezpt->z = 0.0;      /*  compute blending functions , blend control points. */     (k = 0; k < nctrlpts; k++) {         bezblendfcn = c [k] * pow (t, k) * pow (1 - t, n - k);         bezpt->x += ctrlpts [k].x * bezblendfcn;         bezpt->y += ctrlpts [k].y * bezblendfcn;         bezpt->z += ctrlpts [k].z * bezblendfcn;     } }  void bezier (wcpt3d * ctrlpts, glint nctrlpts, glint nbezcurvepts) {     wcpt3d bezcurvept;     glfloat t;     glint *c;      /*  allocate space binomial coefficients  */     c = new glint [nctrlpts];      binomialcoeffs (nctrlpts - 1, c);     (int = 0;  <= nbezcurvepts;  i++) {         t = glfloat (i) / glfloat (nbezcurvepts);         computebezpt (t, &bezcurvept, nctrlpts, ctrlpts, c);         plotpoint (bezcurvept);     }     delete [ ] c; }  int curtransx = 0; int curtransy = 0; void displayfcn (void) {     glclear (gl_color_buffer_bit);   //  clear display window.      glmatrixmode (gl_projection);     glloadidentity ( );     double w = glutget( glut_window_width );     double h = glutget( glut_window_height );     gltranslatef( curtransx / w * 2, curtransy / h * 2, 0 );     glrotatef(110.0, 0.0, 60.0, -100.0);     gluortho2d (xwcmin, xwcmax, ywcmin, ywcmax);      glmatrixmode (gl_modelview);     glloadidentity();      /*  set example number of control points , number of      *  curve positions plotted along bezier curve.     */        glint nctrlpts = 4, nbezcurvepts = 1000;      wcpt3d ctrlpts [4] = {{10.0, -20.0, 0.0}, {10.0, -90.0, 0.0},                           {10.0, 90.0, 0.0}, {10.0, 20.0, 0.0}};       glpointsize (4);     glcolor3f (1.0, 0.0, 1.0);      //  set point color purple       bezier (ctrlpts, nctrlpts, nbezcurvepts);      glutswapbuffers(); }  int btn; int startmousex = 0; int startmousey = 0; int starttransx = 0; int starttransy = 0; void mousecallback(int button, int state, int x, int y) {     btn = button;     if( button == glut_left_button && state == glut_down )     {         startmousex = x;         startmousey = glutget( glut_window_height ) - y;         starttransx = curtransx;         starttransy = curtransy;     }     glutpostredisplay(); }  void motioncallback(int x, int y) {     int curmousex = x;     int curmousey = glutget( glut_window_height ) - y;     if ( btn == glut_left_button )     {          curtransx = starttransx + ( curmousex - startmousex );         curtransy = starttransy + ( curmousey - startmousey );     }     glutpostredisplay(); } /*    void mousecallback(int button, int state, int x, int y) {        if (button == glut_wheel_up && glutgetmodifiers()==glut_active_ctrl) {        }else if (button == glut_wheel_down)            glutpostredisplay();        } */  int main (int argc, char** argv) {     glutinit (&argc, argv);     glutinitdisplaymode (glut_double | glut_rgb);     glutinitwindowposition (50, 50);     glutinitwindowsize (winwidth, winheight);     glutcreatewindow ("bezier curve");      init ( );     glutdisplayfunc (displayfcn);     glutmousefunc(mousecallback);     glutmotionfunc(motioncallback);     glutmainloop ( ); }

you add curve 1 control point, or use gl_points.


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