Use OpenGL to dynamically draw a cubic bezr curve with the mouse

The three-step curve has four control nodes. The one-dimensional calculator principle of OpenGL is used.

 

Program introduction:

For the first time, the left mouse button down is set to 0 control nodes. Press and hold the left mouse button to move dynamically to determine 1 control node,

The second time you left the mouse to go down to 3 control nodes, press and hold the left button to move to confirm 2 control nodes.

Program running:

 

The code just draws a piece of bezeiser as follows:

# Include <Gl/glut. h> <br/> # include <iostream> <br/> # include <vector> <br/> using namespace STD; </P> <p> # define key_point_num 6 <br/> # define control_point_num 4 <br/> # define winwidth1024 <br/> # define winheight768 </P> <p> # define drawoneline (x1, y1, Z1, X2, Y2, Z2) glbegin (gl_lines);/<br/> glvertex3d (X1), (Y1), (Z1 )); glvertex3d (X2), (Y2), (Z2); glend (); </P> <p> enumdraw_flag {<br/> first_line = 0, <Br/> second_line = 1, <br/> end = 2 <br/>}; <br/> intg_iflag = first_line; <br/> intg_viewport [4]; <br/> boolg_bisdown = false; <br/> doubleg_modelmatrix [16]; <br/> doubleg_projmatrix [16]; <br/> double g_vertex [key_point_num] [3]; // six key points, four of which are control nodes. <Br/> doubleg_controlvertex [control_point_num + 3] [3]; </P> <p> ///////////////////////////////// //////////////////////////////////////// /<br/> void Init (); <br/> void display (); <br/> void reshape (int w, int H); <br/> void keyboard (unsigned char key, int X, int y); <br/> void mouse (INT button, int state, int X, int y); <br/> void motion (int x, int y ); </P> <p> int main (INT argc, char ** argv) <br/> {<br/> glutin It (& argc, argv); <br/> gluinitdisplaymode (glu_double | glu_rgb); <br/> gluinitwindowsize (winwidth, winheight); <br/> gluinitwindowposition (100,100 ); <br/> glucreatewindow (argv [0]); </P> <p> Init (); <br/> gludisplayfunc (Display ); <br/> glureshapefunc (reshape); <br/> glukeyboardfunc (keyboard); <br/> glumousefunc (Mouse); <br/> glumotionfunc (motion ); </P> <p> glumainloop (); </P> <p> return 0; <br/>}< /P> <p> void Init (void) <br/>{< br/> glclearcolor (0.0, 0.0, 0.0, 0.0); <br/> glshademodel (gl_smooth ); <br/>}</P> <p> void display (void) <br/>{< br/> glclear (gl_color_buffer_bit ); </P> <p> glpointsize (5.0); <br/> glcolor3f (1.0, 1.0, 0.0); </P> <p> glable (gl_line_stipple ); <br/>{< br/> gllinestipple (1, 0x0101); <br/> If (first_line = g_iflag) <br/> {<br/> drawoneline (g_vertex [0] [0], g_vertex [0] [1], g_vertex [0] [2 ], <Br/> g_vertex [1] [0], g_vertex [1] [1], g_vertex [1] [2]); <br/> drawoneline (g_vertex [0] [0], g_vertex [0] [1], g_vertex [0] [2], <br/> g_vertex [2] [0], g_vertex [2] [1], g_vertex [2] [2]); </P> <p> glbegin (gl_points); <br/>{< br/> glvertex3dv (g_vertex [0]); <br/> glvertex3dv (g_vertex [1]); <br/> glvertex3dv (g_vertex [2]); <br/>} glend (); <br/>}< br/> else if (second_line = g_iflag) <br/>{< br/> drawoneline (g_vertex [3] [0], g_vertex [3] [1], g_vertex [3] [2], <br/> g_vertex [4] [0], g_vertex [4] [1], g_vertex [4] [2]); <br/> drawoneline (g_vertex [3] [0], g_vertex [3] [1], g_vertex [3] [2], <br/> g_vertex [5] [0], g_vertex [5] [1], g_vertex [5] [2]); </P> <p> glbegin (gl_points); <br/>{< br/> glvertex3dv (g_vertex [0]); <br/> glvertex3dv (g_vertex [3]); <br/> glvertex3dv (g_vertex [4]); <br/> glvertex3dv (g_vertex [5]); <br/>} glend (); <br/>}< br />} Gldisable (gl_line_stipple); </P> <p> // extract the control node and draw the bezr curve. <Br/> //////////////////////////////////// /// // <br /> glbegin (gl_points ); <br/> {<br/> for (INT I = 0; I <control_point_num; I ++) <br/> glvertex3dv (& g_controlvertex [I] [0]); <br/>} glend (); </P> <p> glcolor3f (1.0f, 1.0f, 1.0f); <br/> glmap1d (gl_map1_vertex_3, 0.0, 1.0, 3, control_point_num, & g_controlvertex [0] [0]); <br/> glable (gl_map1_vertex_3); <br/> glbegin (gl_line_stri P); <br/>{< br/> for (INT I = 0; I <= 30; I ++) <br/> glevalcoord1f (glfloat) i/30366f); <br/>} glend (); <br/> //////////////////////////////////// /// // </ p> <p> fig (); <br/>}</P> <p> void reshape (int w, int h) <br/> {<br/> glviewport (0, 0, (glsizei) w, (glsizei) H); <br/> glmatrixmode (gl_projection); <br/> glloadidentity (); <br/> If (W <= H) <br/> glortho (-5.0, 5.0,-5.0 * (glfloat) h/(glfloat) W, <br/> 5.0 * (glfloat) h/(glfloat) W,-5.0, 5.0 ); <br/> else <br/> glortho (-5.0 * (glfloat) W/(glfloat) h, <br/> 5.0 * (glfloat) W/(glfloat) H, -5.0, 5.0,-5.0, 5.0); <br/> glmatrixmode (gl_modelview); <br/> glloadidentity (); <br/>}</P> <p> void keyboard (unsigned char key, int X, int y) <br/>{< br/> switch (key) {<br/> Case 27: <br/> exit (0); <br/> break; <br/>}</P> <p> voi D mouse (INT button, int state, int X, int y) <br/>{< br/> // obtain matrix Information <br/> glgetintegerv (gl_viewport, g_viewport ); <br/> glgetdoublev( gl_modelview_matrix, g_modelmatrix); <br/> glgetdoublev( gl_projection_matrix, g_projmatrix ); </P> <p> If (Button = maid & State = maid) <br/>{< br/> g_bisdown = true; </P> <p> double _ 3 dpoint [3]; <br/> Y = g_viewport [3]-y; </P> <p> If (first_line = g_iflag) <br/>{< br/> Glu Unproject (X, Y, 0, <br/> g_modelmatrix, g_projmatrix, g_viewport, <br/> & _ 3 dpoint [0], & _ 3 dpoint [1], & _ 3 dpoint [2]); </P> <p> // all initialization <br/> for (INT I = 0; I <3; I ++) <br/> g_controlvertex [0] [I] = g_vertex [0] [I] = _ 3 dpoint [I]; <br/>}< br/> else if (second_line = g_iflag) <br/>{< br/> gluunproject (X, Y, 0, <br/> g_modelmatrix, g_projmatrix, g_viewport, <br/> & _ 3 dpoint [0], & _ 3 dpoint [1], & _ 3 dpoint [2]); </P> <p> // Save V (3) <br/> for (INT I = 0; I <3; I ++) <br/> g_controlvertex [3] [I] = g_vertex [3] [I] = _ 3 dpoint [I]; <br/>}</P> <p> If (Button = fig & State = fig) <br/>{< br/> g_bisdown = false; </P> <p> g_iflag = (g_iflag + 1) % 3; </P> <p> glusetcursor (glu_cursor_right_arrow ); <br/>}</P> <p> /////////////////////// //////////////////////////////////////// ///////// <br/> // computing control node <br/> void motion (in T x, int y) <br/>{< br/> If (! G_bisdown) <br/> return; </P> <p> maid (FIG); <br/> Y = g_viewport [3]-y; </P> <p> If (first_line = g_iflag) <br/>{< br/> gluunproject (X, Y, 0, <br/> g_modelmatrix, g_projmatrix, g_viewport, <br/> & g_vertex [1] [0], & g_vertex [1] [1], & g_vertex [1] [2]); </P> <p> for (INT I = 0; I <3; I ++) <br/> {<br/> // record control node <br/> g_controlvertex [1] [I] = g_vertex [1] [I]; </P> <p> // v0 is the midpoint of V1 and V2 <br/> g_vertex [2] [I] = 2 * g_vertex [0] [I]-g_vertex [1] [I]; <br/>}< br/> else if (second_line = g_iflag) <br/>{< br/> gluunproject (X, Y, 0, <br/> g_modelmatrix, g_projmatrix, g_viewport, <br/> & g_vertex [5] [0], & g_vertex [5] [1], & g_vertex [5] [2]); </P> <p> for (INT I = 0; I <3; I ++) <br/> {<br/> // V3 is the midpoint of V4 and V5 <br/> g_vertex [4] [I] = 2 * g_vertex [3] [I]- g_vertex [5] [I]; </P> <p> // record control node <br/> g_controlvertex [2] [I] = g_vertex [4] [I]; <br/>}</P> <p> glupostredisplay (); <br/>}< br/>

 

You can splice multiple segments in time.