The document describes code for rendering a 3D snowman scene using OpenGL and GLUT. It includes functions for drawing a snowman, handling user input from the keyboard and mouse, and creating popup menus. It also adds the ability to render text using bitmap fonts by calling the glutBitmapCharacter function and looping through each character in a string.

1. Ring Documentation, Release 1.10
// Set the correct perspective.
gluPerspective(45.0, ratio, 0.1, 100.0)
// Get Back to the Modelview
glMatrixMode(GL_MODELVIEW)
func drawSnowMan
glScalef(scale, scale, scale)
glColor3f(1.0, 1.0, 1.0)
// Draw Body
glTranslatef(0.0 ,0.75, 0.0)
glutSolidSphere(0.75,20,20)
// Draw Head
glTranslatef(0.0, 1.0, 0.0)
glutSolidSphere(0.25,20,20)
// Draw Eyes
glPushMatrix()
glColor3f(0.0,0.0,0.0)
glTranslatef(0.05, 0.10, 0.18)
glutSolidSphere(0.05,10,10)
glTranslatef(-0.1, 0.0, 0.0)
glutSolidSphere(0.05,10,10)
glPopMatrix()
// Draw Nose
glColor3f(red, green, blue)
glRotatef(0.0,1.0, 0.0, 0.0)
glutSolidCone(0.08,0.5,10,2)
glColor3f(1.0, 1.0, 1.0)
func computePos deltaMove
x += deltaMove * lx * 0.1
z += deltaMove * lz * 0.1
func renderScene
if deltaMove
computePos(deltaMove)
ok
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
// Reset transformations
glLoadIdentity()
// Set the camera
gluLookAt( x, 1.0, z,
x+lx, 1.0, z+lz,
0.0, 1.0, 0.0)
62.12. Menu Events 628

2. Ring Documentation, Release 1.10
// Draw ground
glColor3f(0.9, 0.9, 0.9)
glBegin(GL_QUADS)
glVertex3f(-100.0, 0.0, -100.0)
glVertex3f(-100.0, 0.0, 100.0)
glVertex3f( 100.0, 0.0, 100.0)
glVertex3f( 100.0, 0.0, -100.0)
glEnd()
// Draw 36 SnowMen
for i = -3 to 2
for j = -3 to 2
glPushMatrix()
glTranslatef(i*10.0, 0.0, j * 10.0)
drawSnowMan()
glPopMatrix()
next
next
glutSwapBuffers()
// -----------------------------------
// KEYBOARD
// -----------------------------------
func processNormalKeys
key = glutEventKey()
xx = glutEventX()
yy = glutEventY()
glutSetMenu(mainMenu)
switch key
on 27
glutDestroyMenu(mainMenu)
glutDestroyMenu(fillMenu)
glutDestroyMenu(colorMenu)
glutDestroyMenu(shrinkMenu)
shutdown()
on 's'
if not menuFlag
glutChangeToSubMenu(2,"Shrink",shrinkMenu)
ok
on 'c'
if not menuFlag
glutChangeToSubMenu(2,"Color",colorMenu)
ok
off
if key = 27
shutdown()
ok
func pressKey
key = glutEventKey()
62.12. Menu Events 629

3. Ring Documentation, Release 1.10
xx = glutEventX()
yy = glutEventY()
switch key
on GLUT_KEY_UP
deltaMove = 0.5
on GLUT_KEY_DOWN
deltaMove = -0.5
off
func releaseKey
key = glutEventKey()
switch key
on GLUT_KEY_UP
deltaMove = 0
on GLUT_KEY_DOWN
deltaMove = 0
off
// -----------------------------------
// MOUSE
// -----------------------------------
func mouseMove
xx = glutEventX()
yy = glutEventY()
// this will only be true when the left button is down
if xOrigin >= 0
// update deltaAngle
deltaAngle = (xx - xOrigin) * 0.001
// update camera's direction
lx = sin(angle + deltaAngle)
lz = -cos(angle + deltaAngle)
ok
func mouseButton
button = glutEventButton()
state = glutEventState()
xx = glutEventX()
yy = glutEventY()
// only start motion if the left button is pressed
if button = GLUT_LEFT_BUTTON
// when the button is released
if state = GLUT_UP
angle += deltaAngle
xOrigin = -1
else
// state = GLUT_DOWN
62.12. Menu Events 630

4. Ring Documentation, Release 1.10
xOrigin = xx
ok
ok
// -----------------------------------
// MENUS
// -----------------------------------
func processMenuStatus
status = glutEventStatus()
xx = glutEventX()
yy = glutEventY()
if status = GLUT_MENU_IN_USE
menuFlag = 1
else
menuFlag = 0
ok
func processMainMenu
// nothing to do in here
// all actions are for submenus
func processFillMenu
option = glutEventValue()
switch option
on C_FILL
glPolygonMode(GL_FRONT, GL_FILL)
on C_LINE
glPolygonMode(GL_FRONT, GL_LINE)
off
func processShrinkMenu
option = glutEventValue()
switch option
on C_SHRINK
scale = 0.5
on C_NORMAL
scale = 1.0
off
func processColorMenu
option = glutEventValue()
62.12. Menu Events 631

5. Ring Documentation, Release 1.10
switch option
on C_RED
red = 1.0
green = 0.0
blue = 0.0
on C_GREEN
red = 0.0
green = 1.0
blue = 0.0
on C_BLUE
red = 0.0
green = 0.0
blue = 1.0
on C_ORANGE
red = 1.0
green = 0.5
blue = 0.5
off
func createPopupMenus
shrinkMenu = glutCreateMenu(:processShrinkMenu)
glutAddMenuEntry("Shrink",C_SHRINK)
glutAddMenuEntry("NORMAL",C_NORMAL)
fillMenu = glutCreateMenu(:processFillMenu)
glutAddMenuEntry("Fill",C_FILL)
glutAddMenuEntry("Line",C_LINE)
colorMenu = glutCreateMenu(:processColorMenu)
glutAddMenuEntry("Red",C_RED)
glutAddMenuEntry("Blue",C_BLUE)
glutAddMenuEntry("Green",C_GREEN)
glutAddMenuEntry("Orange",C_ORANGE)
mainMenu = glutCreateMenu(:processMainMenu)
glutAddSubMenu("Polygon Mode", fillMenu)
glutAddSubMenu("Color", colorMenu)
// attach the menu to the right button
glutAttachMenu(GLUT_RIGHT_BUTTON)
// this will allow us to know if the menu is active
glutMenuStatusFunc(:processMenuStatus)
// -----------------------------------
// MAIN
// -----------------------------------
func main
// init GLUT and create window
glutInit()
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA)
62.12. Menu Events 632

6. Ring Documentation, Release 1.10
glutInitWindowPosition(100,100)
glutInitWindowSize(320,320)
glutCreateWindow("RingFreeGLUT - Test 10")
// register callbacks
glutDisplayFunc(:renderScene)
glutReshapeFunc(:changeSize)
glutIdleFunc(:renderScene)
glutIgnoreKeyRepeat(1)
glutKeyboardFunc(:processNormalKeys)
glutSpecialFunc(:pressKey)
glutSpecialUpFunc(:releaseKey)
// here are the two new functions
glutMouseFunc(:mouseButton)
glutMotionFunc(:mouseMove)
// OpenGL init
glEnable(GL_DEPTH_TEST)
glEnable(GL_CULL_FACE)
// init Menus
createPopupMenus()
// enter GLUT event processing cycle
glutMainLoop()
Screen Shot
62.13 Using Fonts
Example:
62.13. Using Fonts 633

7. Ring Documentation, Release 1.10
load "freeglut.ring"
load "opengl21lib.ring"
// angle of rotation for the camera direction
angle = 0.0
// actual vector representing the camera's direction
lx=0.0 lz=-1.0
// XZ position of the camera
x=0.0 z=5.0
// the key states. These variables will be zero
//when no key is being presses
deltaAngle = 0.0
deltaMove = 0
xOrigin = -1
// Constant definitions for Menus
C_RED = 1
C_GREEN = 2
C_BLUE = 3
C_ORANGE = 4
C_FILL = 5
C_LINE = 6
// Pop up menu identifiers
fillMenu=NULL
fontMenu=NULL
mainMenu=NULL
colorMenu=NULL
// color for the nose
red = 1.0
blue=0.5
green=0.5
// scale of snowman
scale = 1.0
// menu status
menuFlag = 0
// default font
font = GLUT_BITMAP_TIMES_ROMAN_24
C_INT_GLUT_BITMAP_8_BY_13 = 7
C_INT_GLUT_BITMAP_9_BY_15 = 8
C_INT_GLUT_BITMAP_TIMES_ROMAN_10 = 9
C_INT_GLUT_BITMAP_TIMES_ROMAN_24 = 10
C_INT_GLUT_BITMAP_HELVETICA_10 = 11
C_INT_GLUT_BITMAP_HELVETICA_12 = 12
C_INT_GLUT_BITMAP_HELVETICA_18 = 13
func changeSize
w = glutEventWidth()
62.13. Using Fonts 634

8. Ring Documentation, Release 1.10
h = glutEventHeight()
// Prevent a divide by zero, when window is too short
// (you cant make a window of zero width).
if h = 0
h = 1
ok
ratio = w * 1.0 / h
// Use the Projection Matrix
glMatrixMode(GL_PROJECTION)
// Reset Matrix
glLoadIdentity()
// Set the viewport to be the entire window
glViewport(0, 0, w, h)
// Set the correct perspective.
gluPerspective(45.0, ratio, 0.1, 100.0)
// Get Back to the Modelview
glMatrixMode(GL_MODELVIEW)
func drawSnowMan
glScalef(scale, scale, scale)
glColor3f(1.0, 1.0, 1.0)
// Draw Body
glTranslatef(0.0 ,0.75, 0.0)
glutSolidSphere(0.75,20,20)
// Draw Head
glTranslatef(0.0, 1.0, 0.0)
glutSolidSphere(0.25,20,20)
// Draw Eyes
glPushMatrix()
glColor3f(0.0,0.0,0.0)
glTranslatef(0.05, 0.10, 0.18)
glutSolidSphere(0.05,10,10)
glTranslatef(-0.1, 0.0, 0.0)
glutSolidSphere(0.05,10,10)
glPopMatrix()
// Draw Nose
glColor3f(red, green, blue)
glRotatef(0.0,1.0, 0.0, 0.0)
glutSolidCone(0.08,0.5,10,2)
glColor3f(1.0, 1.0, 1.0)
func renderBitmapString x,y,z,font,string
glRasterPos3f(x, y,z)
for c in string
glutBitmapCharacter(font,ascii(c))
62.13. Using Fonts 635

9. Ring Documentation, Release 1.10
next
func computePos deltaMove
x += deltaMove * lx * 0.1
z += deltaMove * lz * 0.1
func renderScene
if deltaMove
computePos(deltaMove)
ok
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
// Reset transformations
glLoadIdentity()
// Set the camera
gluLookAt( x, 1.0, z,
x+lx, 1.0, z+lz,
0.0, 1.0, 0.0)
// Draw ground
glColor3f(0.9, 0.9, 0.9)
glBegin(GL_QUADS)
glVertex3f(-100.0, 0.0, -100.0)
glVertex3f(-100.0, 0.0, 100.0)
glVertex3f( 100.0, 0.0, 100.0)
glVertex3f( 100.0, 0.0, -100.0)
glEnd()
// Draw 36 SnowMen
for i = -3 to 2
for j = -3 to 2
glPushMatrix()
glTranslatef(i*10.0, 0.0, j * 10.0)
drawSnowMan()
number = (i+3)*6+(j+3)
renderBitmapString(0.0, 0.5, 0.0,font ,""+number)
glPopMatrix()
next
next
glutSwapBuffers()
// -----------------------------------
// KEYBOARD
// -----------------------------------
func processNormalKeys
key = glutEventKey()
xx = glutEventX()
62.13. Using Fonts 636

10. Ring Documentation, Release 1.10
yy = glutEventY()
switch key
on 27
glutDestroyMenu(mainMenu)
glutDestroyMenu(fillMenu)
glutDestroyMenu(colorMenu)
glutDestroyMenu(fontMenu)
Shutdown()
off
func pressKey
key = glutEventKey()
xx = glutEventX()
yy = glutEventY()
switch key
on GLUT_KEY_UP
deltaMove = 0.5
on GLUT_KEY_DOWN
deltaMove = -0.5
off
func releaseKey
key = glutEventKey()
switch key
on GLUT_KEY_UP
deltaMove = 0
on GLUT_KEY_DOWN
deltaMove = 0
off
// -----------------------------------
// MOUSE
// -----------------------------------
func mouseMove
xx = glutEventX()
yy = glutEventY()
// this will only be true when the left button is down
if xOrigin >= 0
// update deltaAngle
deltaAngle = (xx - xOrigin) * 0.001
// update camera's direction
lx = sin(angle + deltaAngle)
lz = -cos(angle + deltaAngle)
ok
62.13. Using Fonts 637