openGL - glortho()

glortho() 함수는 화면상의 좌표축을 설정하는 함수이다.

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01	#include "windows.h"

02	#include "GL/gl.h"

03	#include "GL/glut.h"

04

05	void display(void)

06

{

07	/*  clear all pixels  */

08	glClear (GL_COLOR_BUFFER_BIT);

09	/*  draw white polygon (rectangle) with corners at

10	*  (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0)

11

*/

12	glColor3f (1.0, 1.0, 1.0);

13	glBegin(GL_POLYGON);

14	glVertex3f (0.25, 0.25, 0.0);

15	glVertex3f (0.75, 0.25, 0.0);

16	glVertex3f (0.75, 0.75, 0.0);

17	glVertex3f (0.25, 0.75, 0.0);

18

glEnd();

19	/*  don’t wait!

20	*  start processing buffered OpenGL routines

21

*/

22	glFlush ();

23

}

24	void init (void)

25

{

26	/*  select clearing (background) color       */

27	glClearColor (0.0, 0.0, 0.0, 0.0);

28	/*  initialize viewing values  */

29	glMatrixMode(GL_PROJECTION);

30	glLoadIdentity();

31	glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);

32

}

33

/*

34	*  Declare initial window size, position, and display mode

35	*  (single buffer and RGBA).  Open window with "hello"

36	*  in its title bar.  Call initialization routines.

37	*  Register callback function to display graphics.

38	*  Enter main loop and process events.

39

*/

40	int main(int argc, char** argv)

41

{

42	glutInit(&argc, argv);

43	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);

44	glutInitWindowSize (250, 250);

45	glutInitWindowPosition (100, 100);

46	glutCreateWindow ("hello");

47

init ();

48	glutDisplayFunc(display);

49	glutMainLoop();

50	return 0;   /* ISO C requires main to return int. */

51

}

glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0); 로 설정할 경우의 결과

glOrtho(0.0, 2.0, 0.0, 2.0, -2.0, 2.0); 로 설정할 경우의 결과

대충 정리하자면, 아래 그림과 같다고 할까나~?!

[링크 : http://www.opengl.org/sdk/docs/man/xhtml/glOrtho.xml]