OpenGL demo: Starfield

[Pjot]

Looking into the GL/GLUT API a little bit more, I wondered if it was possible to do some simple 2D drawing. It is not that difficult. Below a demo which needs the GL and the GLUT include files:


'
' Starfield demonstration using GL and GLUT - learning 2D GL/GLUT programming.
'
' Inspired by Cybermonkey's STARS demo:
'   http://forum.basicprogramming.org/index.php/topic,1509.msg9584.html#msg9584
'
' October 2010, PvE - GPL
'
'--------------------------------------------------------------------------------------------

INCLUDE "glut.bac"
INCLUDE "gl.bac"

CONST XSize = 640
CONST YSize = 480

CONST message$ = "S T A R S"

DECLARE x[501], y[501], z[501] TYPE int

SUB draw

LOCAL i, length

glMatrixMode (GL_PROJECTION)
glLoadIdentity

glOrtho(0, XSize, 0, YSize, 0, 1)
glDisable(GL_DEPTH_TEST)
glMatrixMode (GL_MODELVIEW)
glLoadIdentity

glClearColor(0.1, 0.1, 0.1, 0)
glClear(GL_COLOR_BUFFER_BIT)

glColor3f(1, 1, 1)

FOR i = 0 TO 500
glBegin(GL_POINTS)
glVertex2i(x[i], y[i])
glEnd
NEXT

FOR i = 1 TO LEN(message$)
INCR length, glutBitmapWidth(GLUT_BITMAP_HELVETICA_18, ASC(MID$(message$, i)))
NEXT

glColor3f(1, 1, 0)
glRasterPos2f(XSize/2-length/2, YSize/2)

FOR i = 1 TO LEN(message$)
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, ASC(MID$(message$, i)))
NEXT

glutSwapBuffers

END SUB

SUB idle

FOR i = 0 TO 500
x[i] = x[i] - z[i]
IF x[i] < 0 THEN x[i] = x[i] + XSize
NEXT

SLEEP 50

glutPostRedisplay

END SUB

SUB key (NUMBER k, NUMBER x, NUMBER y)

END

END SUB

SUB mainprog (NUMBER argc, STRING argv)

glutInit(ADDRESS(argc), ADDRESS(argv))

glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE)
glutInitWindowSize(XSize, YSize)
glutCreateWindow ("S T A R S")

glutDisplayFunc (ADDRESS (draw))
glutKeyboardFunc (ADDRESS(key))
glutIdleFunc (ADDRESS(idle))

glutMainLoop

END SUB

FOR i = 0 TO 500
x[i] = RANDOM(XSize)
y[i] = RANDOM(YSize)
z[i] = RANDOM(8)+1
NEXT

mainprog(0, "")