/* A framework for writing simple 3D applications with GLUT, with * support for animation, for mouse and keyboard events, and for a * menu. Note that you need to uncomment some lines in main() and * initGL() to enable various features. Drawing code must be * added to display(). See lines marked with "TODO". See the * GLUT documentation at * www.opengl.org/resources/libraries/glut/spec3/node1.html * or the FreeGLUT documentation at * freeglut.sourceforge.net/docs/api.php * * This program must be linked to the GL and glut libraries. * For example, in Linux with the gcc compiler: * * gcc -o executableProg glut-starter.c -lGL -lglut */ #include #include // Consider using freeglut.h instead, if available. #include // (Used only for some information messages to standard out.) #include // (Used only for exit() function.) // --------------------------------- global variables -------------------------------- int width, height; // Size of the drawing area, to be set in reshape(). int frameNumber = 0; // For use in animation. // ------------------------ OpenGL initialization and rendering ----------------------- /* initGL() is called just once, by main(), to do initialization of OpenGL state * and other global state. */ void initGL() { glClearColor(0.0, 0.0, 0.0, 1.0); // background color glEnable(GL_DEPTH_TEST); // Required for 3D drawing, not usually for 2D. // TODO: Uncomment the following 4 lines to do some typical initialization for // lighting and materials. // glEnable(GL_LIGHTING); // Enable lighting. // glEnable(GL_LIGHT0); // Turn on a light. By default, shines from direction of viewer. // glEnable(GL_NORMALIZE); // OpenGL will make all normal vectors into unit normals // glEnable(GL_COLOR_MATERIAL); // Material ambient and diffuse colors can be set by glColor* } // end initGL() /* display() is set up in main() as the function that is called when the window is * first opened, when glutPostRedisplay() is called, and possibly at other times when * the window needs to be redrawn. Usually it will redraw the entire contents of * the window. (Drawing can also be done in other functions, but usually only when * single buffer mode is used. The projection is often set up in intiGL() or reshape() * instead of in display().) */ void display() { // called whenever the display needs to be redrawn glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // For 2D, usually leave out the depth buffer. glMatrixMode(GL_PROJECTION); // Set up a simple orthographic projection, ignoring aspect ratio. glLoadIdentity(); // TODO: should almost certainly use a different projection! glOrtho(-1, 1, -1, 1, -2, 2); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); // Start with no modeling transform. // TODO: INSERT DRAWING CODE HERE glutSwapBuffers(); // (Required for double-buffered drawing.) // (For GLUT_SINGLE display mode, use glFlush() instead.) } /* reshape() is set up in main() as the functin that is called when the window changes size. * It is also called when the window is first opened. The parameters give the size of * the drawing area. If no reshape function is provided, the default is to set the * viewport to match the size of the drawing area. */ void reshape(int w, int h) { width = w; // Save width and height for possible use elsewhere. height = h; glViewport(0,0,width,height); // If you have a reshape function, you MUST call glViewport! // TODO: INSERT ANY OTHER CODE TO ACCOUNT FOR WINDOW SIZE (maybe set projection here). printf("Reshaped to width %d, height %d\n", width, height); } // --------------- support for animation ------------------------------------------ /* You can call startAnimation() to run an animation. A frame will be drawn every * 30 milliseconds (can be changed in the call to glutTimerFunc. The global frameNumber * variable will be incremented for each frame. Call pauseAnimation() to stop animating. */ int animating = 0; // 0 or 1 to indicate whether an animation is in progress; // do not change directly; call startAnimation() and pauseAnimation() void updateFrame() { // this is called before each frame of the animation. // TODO: INSERT CODE TO UPDATE DATA USED IN DRAWING A FRAME frameNumber++; printf("frame number %d\n", frameNumber); } void timerFunction(int timerID) { // used for animation; do not call this directly if (animating) { updateFrame(); glutTimerFunc(30, timerFunction, 0); // Next frame in 30 milliseconds. glutPostRedisplay(); // Causes display() to be called. } } void startAnimation() { // call this to start or restart the animation if ( ! animating ) { animating = 1; glutTimerFunc(30, timerFunction, 0); } } void pauseAnimation() { // call this to pause the animation animating = 0; } // --------------- keyboard event functions --------------------------------------- /* charTyped() is set up in main() to be called when the user types a character. * The ch parameter is an actual character such as 'A', '7', or '@'. The parameters * x and y give the mouse position, in pixel coordinates, when the character was typed, * with (0,0) at the UPPER LEFT. */ void charTyped(unsigned char ch, int x, int y) { // TODO: INSERT CHARACTER-HANDLING CODE glutPostRedisplay(); // Causes display() to be called. printf("User typed %c with ASCII code %d, mouse at (%d,%d)\n", ch, ch, x, y); } /* specialKeyPressed() is set up in main() to be called when the user presses certaub keys * that do NOT type an actual character, such as an arrow or function key. The * key parameter is a GLUT constant such as GLUT_KEY_LEFT, GLUT_KEY_RIGHT, * GLUT_KEY_UP and GLUT_KEY_DOWN for the arrow keys; GLUT_KEY_HOME for the home key, * and GLUT_KEY_F1 for a funtion key. Note that escape, backspace, and delete are * considered to be characters and result in a call to charTyped. The x and y * parameters give the mouse position when the key was pressed. */ void specialKeyPressed(int key, int x, int y) { // TODO: INSERT KEY-HANDLING CODE glutPostRedisplay(); // Causes display() to be called. printf("User pressed special key with code %d; mouse at (%d,%d)\n", key, x, y); } // --------------- mouse event functions with some typical support code for dragging ----------------- int dragging; // 0 or 1 to indicate whether a drag operation is in progress int dragButton; // which button started the drag operation int startX, startY; // mouse position at start of drag int prevX, prevY; // previous mouse position during drag /* mouseUpDown() is set up in main() to be called when the user presses or releases * a mutton ont he mouse. The button paramter is one of the contants GLUT_LEFT_BUTTON, * GLUT_MIDDLE_BUTTON, or GLUT_RIGHT_BUTTON. The buttonState is GLUT_UP or GLUT_DOWN and * tells whether this is a mouse press or a mouse release event. x and y give the * mouse position in pixel coordinates, with (0,0) at the UPPER LEFT. */ void mouseUpOrDown(int button, int buttonState, int x, int y) { // called to respond to mouse press and mouse release events if (buttonState == GLUT_DOWN) { // a mouse button was pressed if (dragging) return; // Ignore a second button press during a draw operation. // TODO: INSERT CODE TO RESPOND TO MOUSE PRESS dragging = 1; // Might not want to do this in all cases dragButton = button; startX = prevX = x; startY = prevY = y; printf("Mouse button %d down at (%d,%d)\n", button, x, y); } else { // a mouse button was released if ( ! dragging || button != dragButton ) return; // this mouse release does not end a drag operation. dragging = 0; // TODO: INSERT CODE TO CLEAN UP AFTER THE DRAG (generally not needed) printf("Mouse button %d up at (%d,%d)\n", button, x, y); } } /* mouseDragged() is set up in main() to be called when the user moves the mouse, * but only when one or more mouse buttons are pressed. x and y give the position * of the mouse in pixel coordinates. */ void mouseDragged(int x, int y) { // called to respond when the mouse moves during a drag if ( ! dragging ) return; // This is not part of a drag that we want to respond to. // TODO: INSERT CODE TO RESPOND TO NEW MOUSE POSITION prevX = x; prevY = y; printf("Mouse dragged to (%d,%d)\n", x, y); } // ------------------------------- Menu support ---------------------------------- /* A function to be called when the user selects a command from the menu. The itemCode * is the value that was associated with the command in the call to glutAddMenuEntry() * that added the command to the menu. */ void doMenu( int itemCode ) { if (itemCode == 1) { exit(0); } // TODO: Add support for other commands. } /* createMenu() is called in main to add a pop-up menu to the window. The menu * pops up when the user right-clicks the display. */ void createMenu() { glutCreateMenu(doMenu); // doMenu() will be called when the user selects a command from the menu. glutAddMenuEntry("Quit", 1); // Add a command named "Quit" to the menu with item code = 1. // The code will be passed as a parameter to doMenu() when // the user selects this command from the menu. // TODO: Add additional menu items. (It is also possible to have submenus.) glutAttachMenu(GLUT_RIGHT_BUTTON); // Menu will appear when user RIGHT-clicks the display. } // ----------------- main routine ------------------------------------------------- int main(int argc, char** argv) { glutInit(&argc, argv); // Allows processing of certain GLUT command line options glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH); // Usually, omit GLUT_DEPTH for 2D drawing! glutInitWindowSize(500,500); // size of display area, in pixels glutInitWindowPosition(100,100); // location in window coordinates glutCreateWindow("OpenGL Program"); // parameter is window title glutDisplayFunc(display); // call display() when the window needs to be redrawn glutReshapeFunc(reshape); // call reshape() when the size of the window changes /* TODO: Uncomment one or both of the next two lines for keyboard event handling. */ //glutKeyboardFunc(charTyped); // call charTyped() when user types a character //glutSpecialFunc(specialKeyPressed); // call specialKeyPressed() when user presses a special key /* TODO: Uncomment the next line to handle mouse presses; the next two for mouse dragging. */ //glutMouseFunc(mouseUpOrDown); // call mouseUpOrDown() for mousedown and mouseup events //glutMotionFunc(mouseDragged); // call mouseDragged() when mouse moves, only during a drag gesture /* TODO: Uncomment the next line to add a popup menu */ //createMenu(); /* TODO: Uncomment the next line to start a timer-controlled animation. */ //startAnimation(); glutMainLoop(); // Run the event loop! This function does not return. return 0; }