// sample4.C // // This example code extends sample1.C to allow the user // to toggle the colour of the cube; it also rotates the cube. // // CS414 - The University of British Columbia // Dept. of Computer Science // Last update: January 24, 1997 // //#include // <stream.h> #include // <stdlib.h> #include // <GL/glut.h> // Prototypes for module global functions static void initWin(); static void winDisplay(); static void winKbd( unsigned char, int, int ); static void winReshape( int, int ); static void winMouse( int, int, int, int ); static void setupCameraView( void ); static void drawScene( void ); static void drawCube( void ); static void checkHits( int, int ); static void processHits( int, GLuint * ); // Local Defines #define ROTATION_INC 13.0 // advances rotation by 13 degrees #define CUBE_NAME 0 #define X_PICK_SIZE 5 // pick region is 5 x 5 pixels in size #define Y_PICK_SIZE 5 // Global variables float Rotation = 0.0; int Active[1] = { 0 }; int main( int argc, char *argv[] ) { glutInit( &argc, argv ); glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH ); initWin(); glutMainLoop(); return 1; } static void initWin() // This function initializes the OpenGL window and registers the callback // routines { glutCreateWindow( "Sample 4 OpenGL/GLUT" ); glutDisplayFunc( winDisplay ); // Window callbacks glutKeyboardFunc( winKbd ); glutReshapeFunc( winReshape ); glutMouseFunc( winMouse ); glClearColor( 0, 0, 0, 0 ); // Default background colour glEnable( GL_DEPTH_TEST ); // We have to enable depth buffering glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); glMatrixMode( GL_PROJECTION ); glLoadIdentity(); } // End function initWin static void winDisplay() // This callback function handles window redisplay requests { setupCameraView(); drawScene(); glutSwapBuffers(); } // End function winDisplay static void winKbd( unsigned char key, int x, int y ) // This callback function handles keyboard strokes // // key: Key pressed by user // x: X-position of mouse // y: Y-position of mouse { switch( key ) { case 'q': // Quit program case 'Q': exit( 0 ); case 'r': // Rotate the object case 'R': Rotation += ROTATION_INC; // check limits on the value of Rotation if( Rotation >= 360.0 ) Rotation -= 360.0; break; default: break; } // The next call is VERY important! Without it, the // program doesn't display anything glutPostRedisplay(); } // End function winKbd static void winReshape( int w, int h ) // This callback function resets the viewport to cover the entire window // // w: Current width of window // h: Current height of window { glViewport( 0, 0, w, h ); } // End function winReshape static void winMouse( int button, int state, int x, int y ) // This callback function handles mouse button events // // button: The button with the altered state // state: The up/down state of the mouse button // x, y: The position of the mouse cursor { int hits; if( state == GLUT_DOWN ) { switch( button ) { case GLUT_LEFT_BUTTON: checkHits( x, y ); break; } } } // End function winMouse #define BUFSIZE 256 // select buffer will be 256 ints in size static void checkHits( int x, int y ) // This function sets up picking and calls the processing function // // x, y: The position at which picking is to be performed { GLuint selectBuf[BUFSIZE]; GLint hits; GLint viewport[4]; GLdouble matrix[16]; glGetIntegerv( GL_VIEWPORT, viewport ); // get viewport coordinates glSelectBuffer( BUFSIZE, selectBuf ); glRenderMode( GL_SELECT ); glInitNames(); glMatrixMode( GL_PROJECTION ); glPushMatrix(); setupCameraView(); glMatrixMode( GL_PROJECTION ); glGetDoublev( GL_PROJECTION_MATRIX, matrix ); glLoadIdentity(); gluPickMatrix( (double)x, (double)( viewport[3] - y ), X_PICK_SIZE, Y_PICK_SIZE, viewport ); // creates picking region near cursor location glMultMatrixd( matrix ); drawScene(); glMatrixMode( GL_PROJECTION ); glPopMatrix(); hits = glRenderMode( GL_RENDER ); processHits( hits, selectBuf ); } // End function checkHit static void processHits( int hits, GLuint *buffer ) // This function steps through the selection buffer, and updates // any info which is affected by the newly picked objects in the scene. // IMPORTANT: This is a simple implementation (it won't do everything) and // many of the things it does are not really needed in this case... // // hits: The number of hits which occurred // buffer: A pointer to the selection buffer { int i, j; GLuint *ptr = buffer; GLuint nameStackDepth, currname, zmin, zmax; for( i = 0; i < hits; i++ ) { // There will really only be <=1 hit nameStackDepth = *ptr++; // Not really needed here zmin = *ptr++; // Not really needed here zmax = *ptr++; // Not really needed here for( j = 0; j < nameStackDepth; j++ ) { // Not really needed here currname = *ptr++; // Not really needed here } Active[currname] = !Active[currname]; // Toggle the state of the cube } glutPostRedisplay(); } // End function processHits static void drawCube() // This function draws a cube which is rotated according to the global // variable Rotation { glPushMatrix(); glRotatef( Rotation, 1.0, 1.0, 1.0 ); glutWireCube( 1.0 ); // draws cube of size 1.0 glPopMatrix(); } // End function drawCube static void setupCameraView( void ) // This procedure sets up the projection, camera position, and orientation. { glMatrixMode( GL_PROJECTION ); glLoadIdentity(); gluPerspective( 45.0, 1.0, 0.1, 100.0 ); glTranslatef( 0, 0, -5 ); // Move default camera position // away from origin } // End function setupCameraView static void drawScene( void ) // This procedure draws the current scene, assuming that the camera view // has been set-up. { glMatrixMode( GL_MODELVIEW ); // glClear below clears also the depth buffer now glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); glColor3f( 1.0, 1.0, 0.0 ); // Set colour to yellow if( Active[CUBE_NAME] ) glColor3f( 1.0, 1.0, 0.0 ); // Set colour to yellow else glColor3f( 0.0, 1.0, 0.0 ); // Set colour to green glPushName( CUBE_NAME ); // Identify object to be drawn // (no effect if not picking) drawCube(); glPopName(); glFlush(); } // End function drawScene