The Ring programming language version 1.5.3 book - Part 64 of 184
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The document describes how to handle window resize events in OpenGL. It provides code for a function called changeSize() that gets called on window resize. This function updates the viewport and projection matrix to adjust for the new window size and aspect ratio, preventing distortion. It also handles preventing a divide by zero if the window width becomes zero.
The Ring programming language version 1.5.3 book - Part 64 of 184
- 1. Ring Documentation, Release 1.5.3 54.7 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) 54.7. Window Resize Event 505
- 2. Ring Documentation, Release 1.5.3 // Get Back to the Modelview glMatrixMode(GL_MODELVIEW) 54.8 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() 54.8. Triangle Rotation 506
- 3. Ring Documentation, Release 1.5.3 // 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 54.9 Keyboard Events and Colors Example: load "freeglut.ring" load "opengl21lib.ring" 54.9. Keyboard Events and Colors 507
- 4. Ring Documentation, Release 1.5.3 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 54.9. Keyboard Events and Colors 508
- 5. Ring Documentation, Release 1.5.3 // (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 54.9. Keyboard Events and Colors 509
- 6. Ring Documentation, Release 1.5.3 54.10 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) 54.10. The Camera 510
- 7. Ring Documentation, Release 1.5.3 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 54.10. The Camera 511
- 8. Ring Documentation, Release 1.5.3 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) 54.10. The Camera 512
- 9. Ring Documentation, Release 1.5.3 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 54.10. The Camera 513
- 10. Ring Documentation, Release 1.5.3 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) 54.10. The Camera 514