1 / 22

Chapter 3 modified by Ray Wisman rwisman@ius

Working with Callbacks Chapter 3 modified by Ray Wisman rwisman@ius.edu Ed Angel Professor of Computer Science, Electrical and Computer Engineering, and Media Arts University of New Mexico Objectives Learn to build interactive programs using GLUT callbacks Mouse Keyboard Reshape

issac
Télécharger la présentation

Chapter 3 modified by Ray Wisman rwisman@ius

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Working with Callbacks Chapter 3modified by Ray Wisman rwisman@ius.edu Ed Angel Professor of Computer Science, Electrical and Computer Engineering, and Media Arts University of New Mexico Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  2. Objectives • Learn to build interactive programs using GLUT callbacks • Mouse • Keyboard • Reshape • Introduce menus in GLUT Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  3. The mouse callback glutMouseFunc(mymouse) void mymouse(GLint button, GLint state, GLint x, GLint y) • Callback passes • which button (GLUT_LEFT_BUTTON, GLUT_MIDDLE_BUTTON, GLUT_RIGHT_BUTTON) caused event • state of that button (GLUT_UP, GLUT_DOWN) • Position in window (x,y) where y=0 is upper-left. Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  4. Positioning • The position in the screen window is usually measured in pixels with the origin at the top-left corner • Artifact of screen refresh done from top to bottom • OpenGL uses a world coordinate system with origin at the bottom left • Must invert y coordinate returned by callback by height of window • y = h – y; (0,0) h w Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  5. Obtaining the window size • To invert the y position we need the window height • Height can change during program execution • Track with a global variable • New height returned to reshape callback that we will look at in detail soon • Can also use query functions • glGetIntegerv • glGetFloatv to obtain any value that is part of the state Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  6. Terminating a program • In our original programs, there was no way to terminate them through OpenGL • We can use the simple mouse callback void mouse(int btn, int state, int x, int y) { if(btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN) exit(0); } Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  7. Using the mouse position • In the next example, we draw a small square at the location of the mouse each time the left mouse button is clicked • This example does not use the display callback but one is required by GLUT; the function is called when window opened/resized. mydisplay(){ glClear(GL_COLOR_BUFFER_BIT); glFlush(); } Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  8. Drawing squares at cursor location on left mouse click void mymouse(int btn, int state, int x, int y) { if(btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN) exit(0); if(btn==GLUT_LEFT_BUTTON && state==GLUT_DOWN) drawSquare(x, y); } void drawSquare(int x, int y) { y = h - y; /* window height h, invert y */ glColor3ub( (char) rand()%256, // Random (char) rand )%256, // color (char) rand()%256); glRecti(x-size, y-size, x+size, y+size); glFlush(); } Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  9. Using the motion callback • We can draw squares (or anything else) continuously as long as a mouse button is depressed by using the motion callback • glutMotionFunc( drawSquare ) • We can draw squares without depressing a button using the passive motion callback • glutPassiveMotionFunc( drawSquare ) • Because no display callback is made clearing the screen, a line of squares is displayed Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  10. Using the keyboard glutKeyboardFunc( mykey ) void mykey(unsigned char key, int x, int y) • Returns ASCII code of key depressed and mouse location void mykey(unsigned char key, int x, int y) { if(key == ‘Q’ | key == ‘q’) exit(0); } Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  11. Special and Modifier Keys • GLUT defines the special keys in glut.h • Function key 1: GLUT_KEY_F1 • Up arrow key: GLUT_KEY_UP • if(key == ‘GLUT_KEY_F1’ …… • Can also check of one of the modifiers • GLUT_ACTIVE_SHIFT • GLUT_ACTIVE_CTRL • GLUT_ACTIVE_ALT is depressed by glutGetModifiers() • Allows emulation of three-button mouse with one- or two-button mice Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  12. Reshaping the window • We can reshape and resize the OpenGL display window by pulling the corner of the window • What happens to the display? • Must redraw from application • Two possibilities • Display part of world • Display whole world but force to fit in new window • Can alter aspect ratio Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  13. Reshape possiblities original reshaped Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  14. The Reshape callback glutReshapeFunc(myreshape) void myreshape( int w, int h) • Receives width and height of new window (in pixels) • A redisplay is posted automatically at end of execution of the callback • GLUT has a default reshape callback but you probably want to define your own • The reshape callback is good place to put viewing functions because it is invoked when the window is first opened • Without reshape. With reshape. Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  15. Example Reshape • This reshape preserves shapes by making the viewport and world window have the same aspect ratio • Suppose initially: gluOrtho2D(-2.0, 2.0, -2.0, 2.0 ); gluOrtho2D( left, right, bottom, top ) void myReshape(int w, int h) { glViewport(0, 0, w, h); /* x, y, w, h */ glMatrixMode(GL_PROJECTION); /* switch matrix mode */ glLoadIdentity(); if (w <= h) /* change bottom and top */ gluOrtho2D(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w, 2.0 * (GLfloat) h / (GLfloat) w); else /* change lower-left x and y */ gluOrtho2D(-2.0 * (GLfloat) w / (GLfloat) h, 2.0 * (GLfloat) w / (GLfloat) h, -2.0, 2.0); glMatrixMode(GL_MODELVIEW); /* return to modelview mode */ } Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  16. Example Reshape • Suppose initially: gluOrtho2D(-2.0, 2.0, -2.0, 2.0 ); gluOrtho2D( left, right, bottom, top ) • Change (width, height) from (100,100) to (50,100) • Viewport aspect ratio (width-to-height) =50/100 = ½ • Clipping rectangle aspect ratio = 4/8 = ½ void myReshape(int w, int h) { glViewport(0, 0, 50, 100); /* x, y, w, h */ if (50 <= 100) /* change bottom and top */ gluOrtho2D(-2.0, 2.0, -2.0 * 100 / 50, 2.0 * 100 / 50; 50 4 100 (0,0) -4 -2 2 Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  17. Toolkits and Widgets • Most window systems provide a toolkit or library of functions for building user interfaces that use special types of windows called widgets • Widget sets include tools such as • Menus • Slidebars • Dials • Input boxes • But toolkits tend to be platform dependent • GLUT provides a few widgets including menus Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  18. Menus • GLUT supports pop-up menus • A menu can have submenus • Three steps • Define entries for the menu • Define action for each menu item • Action carried out if entry selected • Attach menu to a mouse button Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  19. Defining a simple menu • In main.c menu_id = glutCreateMenu(mymenu); glutAddmenuEntry(“clear Screen”, 1); gluAddMenuEntry(“exit”, 2); glutAttachMenu(GLUT_RIGHT_BUTTON); clear screen exit entries that appear when right mouse button depressed identifiers Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  20. Menu actions • Menu callback • Note each menu has an id that is returned when it is created • Add submenus by glutAddSubMenu(char *submenu_name, submenu id) void mymenu(int id) { if(id == 1) glClear(); if(id == 2) exit(0); } entry in parent menu Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  21. Menu Example int size=1; void display() { glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0, 1.0, 1.0); glRectf(-size, -size, size, size); glFlush(); } void menu(int id) { switch(id) { case 1 : exit(0); case 2 : if( size < 10) size++;break; case 3 : if( size > 1) size--;break; } glutPostRedisplay(); } int main(int argc, char** argv){ : : glutCreateMenu(menu); glutAddMenuEntry("quit", 1); glutAddMenuEntry("+", 2); glutAddMenuEntry("-", 3); glutAttachMenu(GLUT_RIGHT_BUTTON); glutMainLoop(); } Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

  22. Other functions in GLUT • Dynamic Windows • Create and destroy during execution • Subwindows • Multiple Windows • Changing callbacks during execution • Timers • Portable fonts • glutBitmapCharacter • glutStrokeCharacter Angel: Interactive Computer Graphics 4E © Addison-Wesley 2005

More Related