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androun

OpenGL opengl question

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when I use the gluPerspective for tarce a sphere and when i extract the image of depth (z buffer) ,i see a value is different of the reality when i trace the sphere,and when i use the glortho i extract the reel value why??? and here is the program void Dessiner() { glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); glColor3f(1.0,1.0,1.0); //glMatrixMode( GL_MODELVIEW ); glLoadIdentity( ); gluLookAt(3,0,0,0.0,0.0,0,0,0,1); //glScalef(1.0,2.0,1.0); //activer son utilisation : après la création de la fenêtre OpenGL il faut simplement appeler : glEnable(GL_DEPTH_TEST); //le réinitialiser à chaque nouvelle image, en même temps que le buffer des pixels : //glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) ; glutWireSphere(1.0,50,25); glFlush(); IplImage *rendugl=cvCreateImage(cvSize(640,480),IPL_DEPTH_32F,1); glReadPixels(0,0,640,480,GL_DEPTH_COMPONENT,GL_FLOAT,rendugl->imageData); rendugl->origin=IPL_ORIGIN_BL; double mind1,maxd1; CvPoint locmin; CvPoint locmax; cvMinMaxLoc(rendugl,&mind1,&maxd1,&locmin,&locmax,0); fprintf(stderr,"Z min : %f,\t Z max : %f\n",mind1,maxd1); cvNamedWindow("depth",1); cvShowImage("depth",rendugl); } void reshape(int w,int h) { glViewport(0,0,(GLsizei) w,(GLsizei) h); glMatrixMode(GL_PROJECTION ); glLoadIdentity(); //glFrustum(-1.0,1.0,-1.0,1.0,1.5,20.0); //gluPerspective(70,(GLdouble)640/480,1,3); glOrtho(-3,3,-3*(GLdouble)480/640,3*(GLdouble)480/640,1,3); //glDepthRange(1,3); glMatrixMode(GL_MODELVIEW); glEnable(GL_DEPTH_TEST); } int main(int argc ,char **argv) { glutInit(&argc, argv); //glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH); glutInitDisplayMode(GLUT_SINGLE| GLUT_RGB | GLUT_DEPTH); glutInitWindowSize(640,480); glutInitWindowPosition(100,100); glutCreateWindow(argv[0]); glutDisplayFunc(Dessiner); glutReshapeFunc(reshape); glReadBuffer(GL_FRONT); //cvWaitKey(0); glutMainLoop (); return 0; }

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Quote:
Original post by androun
when I use the gluPerspective for tarce a sphere and when i extract the image of depth (z buffer) ,i see a value is different of the reality when i trace the sphere,and when i use the glortho i extract the reel value why???


i cant make out this sentence...
can you elaborate your question?

it is also a really good idea to write your code in english.
having french comments just make the code unreadable.

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why the use of the gluperspective(for perspective projection) doesn't return the reel value of the coordannate Z in the Z-Buffer

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