The Ring programming language version 1.9 book - Part 64 of 210

1. Ring Documentation, Release 1.9
61.7 Window Resize Event
Example:
load "freeglut.ring"
load "opengl21lib.ring"
func main
// init GLUT and create window
glutInit()
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA)
glutInitWindowPosition(100,100)
glutInitWindowSize(320,320)
glutCreateWindow("RingFreeGLUT - Test 4")
glutDisplayFunc(:renderScene)
glutReshapeFunc(:changeSize)
glutMainLoop()
func renderScene
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
glBegin(GL_TRIANGLES)
glVertex3f(-2,-2,-5.0)
glVertex3f(2,0.0,-5.0)
glVertex3f(0.0,2,-5.0)
glEnd()
glutSwapBuffers()
func changesize
h = glutEventHeight()
w = glutEventWidth()
// 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,ratio,1,100)
61.7. Window Resize Event 599

2. Ring Documentation, Release 1.9
// Get Back to the Modelview
glMatrixMode(GL_MODELVIEW)
61.8 Triangle Rotation
Example:
load "freeglut.ring"
load "opengl21lib.ring"
angle = 0
func main
// init GLUT and create window
glutInit()
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA)
glutInitWindowPosition(100,100)
glutInitWindowSize(320,320)
glutCreateWindow("RingFreeGLUT - Test 5")
glutDisplayFunc(:renderScene)
glutReshapeFunc(:changeSize)
glutIdleFunc(:renderScene)
glutMainLoop()
func renderScene
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
// Reset transformations
glLoadIdentity()
// Set the camera
gluLookAt( 0.0, 0.0, 10.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0)
glRotatef(angle, 0.0, 1.0, 0.0)
glBegin(GL_TRIANGLES)
glVertex3f(-2.0,-2.0, 0.0)
glVertex3f( 2.0, 0.0, 0.0)
glVertex3f( 0.0, 2.0, 0.0)
glEnd()
angle+=0.1
glutSwapBuffers();
func changesize
h = glutEventHeight()
w = glutEventWidth()
61.8. Triangle Rotation 600

3. Ring Documentation, Release 1.9
// 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,ratio,1,100)
// Get Back to the Modelview
glMatrixMode(GL_MODELVIEW)
Screen Shot
61.9 Keyboard Events and Colors
Example:
load "freeglut.ring"
load "opengl21lib.ring"
61.9. Keyboard Events and Colors 601

4. Ring Documentation, Release 1.9
angle = 0
red=1.0
blue=1.0
green=1.0
func main
// init GLUT and create window
glutInit()
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA)
glutInitWindowPosition(100,100)
glutInitWindowSize(320,320)
glutCreateWindow("RingFreeGLUT - Test 6")
glutDisplayFunc(:renderScene)
glutReshapeFunc(:changeSize)
glutIdleFunc(:renderScene)
// here are the new entries
glutKeyboardFunc(:processNormalKeys)
glutSpecialFunc(:processSpecialKeys)
glutMainLoop()
func renderScene
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
// Reset transformations
glLoadIdentity()
// Set the camera
gluLookAt( 0.0, 0.0, 10.0,
0.0, 0.0, 0.0,
0.0, 1.0, 0.0)
glRotatef(angle, 0.0, 1.0, 0.0)
glColor3f(red,green,blue);
glBegin(GL_TRIANGLES)
glVertex3f(-2.0,-2.0, 0.0)
glVertex3f( 2.0, 0.0, 0.0)
glVertex3f( 0.0, 2.0, 0.0)
glEnd()
angle+=0.1
glutSwapBuffers();
func changesize
h = glutEventHeight()
w = glutEventWidth()
// Prevent a divide by zero, when window is too short
61.9. Keyboard Events and Colors 602

5. Ring Documentation, Release 1.9
// (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,ratio,1,100)
// Get Back to the Modelview
glMatrixMode(GL_MODELVIEW)
func processNormalKeys
key = GLUTEventKey()
if key = 27
shutdown()
ok
func processSpecialKeys
key = GLUTEventKey()
switch key
on GLUT_KEY_F1
red = 1.0
green = 0.0
blue = 0.0
on GLUT_KEY_F2
red = 0.0
green = 1.0
blue = 0.0
on GLUT_KEY_F3
red = 0.0
green = 0.0
blue = 1.0
off
Screen Shot
61.9. Keyboard Events and Colors 603

6. Ring Documentation, Release 1.9
61.10 The Camera
Example:
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
func drawSnowMan
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)
61.10. The Camera 604

7. Ring Documentation, Release 1.9
glutSolidSphere(0.05,10,10)
glTranslatef(-0.1, 0.0, 0.0)
glutSolidSphere(0.05,10,10)
glPopMatrix()
// Draw Nose
glColor3f(1.0, 0.5 , 0.5)
glutSolidCone(0.08,0.5,10,2)
func changeSize
w = glutEventWidth()
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 processNormalKeys
key = glutEventKey()
if key = 27
shutdown()
ok
func renderScene
// Clear Color and Depth Buffers
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
// Reset transformations
glLoadIdentity()
// Set the camera
61.10. The Camera 605

8. Ring Documentation, Release 1.9
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,j * 10.0)
drawSnowMan()
glPopMatrix()
next
next
glutSwapBuffers()
func processSpecialKeys
key = glutEventKey()
fraction = 0.1
switch key
on GLUT_KEY_LEFT
angle -= 0.01
lx = sin(angle)
lz = -cos(angle)
on GLUT_KEY_RIGHT
angle += 0.01
lx = sin(angle)
lz = -cos(angle)
on GLUT_KEY_UP
x += lx * fraction
z += lz * fraction
on GLUT_KEY_DOWN
x -= lx * fraction
z -= lz * fraction
off
func main
// init GLUT and create window
glutInit()
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA)
61.10. The Camera 606

9. Ring Documentation, Release 1.9
glutInitWindowPosition(100,100)
glutInitWindowSize(320,320)
glutCreateWindow("RingFreeGLUT - Test 7")
// register callbacks
glutDisplayFunc(:renderScene)
glutReshapeFunc(:changeSize)
glutIdleFunc(:renderScene)
glutKeyboardFunc(:processNormalKeys)
glutSpecialFunc(:processSpecialKeys)
// OpenGL init
glEnable(GL_DEPTH_TEST)
// enter GLUT event processing cycle
glutMainLoop()
Screen Shot
Another Example:
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
61.10. The Camera 607

10. Ring Documentation, Release 1.9
deltaMove = 0
func changeSize
w = glutEventWidth()
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
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(1.0, 0.5 , 0.5)
glRotatef(0.0,1.0, 0.0, 0.0)
glutSolidCone(0.08,0.5,10,2)
61.10. The Camera 608