StackOverflow2013

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POOpenGL glViewport() (resetting coordinates)
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copied!<p>I have a problem with glViewport. In my liitle programm i have two viewports. I can draw a form (with the motionfunc) in one of those viewports and in the other a line is automatically drawn. So far so good.. When i try to draw something with mousefunc the viewport is in a total different place. And it is very difficult to find the new correct coordinates for that viewport. Is there a possibility to reset the coordinates.. I cant use glLoadIdentity in mouse or motion because then nothing is displayed.</p> <p>I hope you understand what i mean. It is a bit difficult to explain.</p> <p>OK here a codesnippet....</p> <pre><code>void mouse (int button, int state, int mx, int my) { if (modus == 0 && button==GLUT_LEFT_BUTTON && state != GLUT_DOWN) { ... } else if (modus == 1 && button==GLUT_LEFT_BUTTON && state == GLUT_DOWN) { **glViewport(10,10 , sw_w1, sw_h1);** //the drawing is much higher than in the first viewport in motion. //But it should be the same viewport like the first in motion. glBegin()...glEnd() glFlush(); } } void motion(int mousex,int mousey) { GLdouble h=12; GLdouble winkel=360/h; Line liste[num]; liste[++last].x =(mousex)-((sw_w1+2*GAP)/2); liste[last].y =(mousey)-((sw_h1+2*GAP)/2); if (modus==0 && gruppe == 0) { if (last>=1) { glViewport(10, 10, sw_w1, sw_h1); //works fine glColor3d(R, G, B); for(h+1;h>0;h--){ glRotated(winkel, 0, 0, 1); glBegin(GL_LINE_STRIP); for(int i=last-1;i<=last;i++){ glVertex2i(liste[i].x,liste[i].y); } glEnd(); } glLineWidth(linewidth+0.5); glColor3f(1, 0, 0); glBegin(GL_LINE_STRIP); for(int i=last-1;i<=last;i++){ glVertex2i(liste[i].x,liste[i].y); } glEnd(); glViewport(1020,10 , sw_w2, sw_h2); //works fine glColor3f(1, 0, 0); glBegin(GL_LINE_STRIP); for(int i=last-1;i<=last;i++){ glVertex2i(liste[i].x,liste[i].y); } glEnd(); } glFlush(); } } </code></pre> <p>The second and third viewport works fine. The first one is the same as the second but the picture is displayed much higher.Why is that so? And how could i change it so that i get the same viewport like the second one. I hope you now understand what i mean.</p>

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