Sun Mar 20, 2011 8:55 pm
/*
* SimpleAnim.c
*
* Example program illustrating a simple use
* of OpenGL to animate motion. Creates rotating
* overlapping triangles.
*
* Author: Samuel R. Buss
*
* Software accompanying the book
* 3D Computer Graphics: A Mathematical Introduction with OpenGL,
* by S. Buss, Cambridge University Press, 2003.
*
* Software is "as-is" and carries no warranty. It may be used without
* restriction, but if you modify it, please change the filenames to
* prevent confusion between different versions.
* Bug reports: Sam Buss, [email protected].
* Web page: http://math.ucsd.edu/~sbuss/MathCG
*
* USAGE:
* Press "r" key to toggle (off and on) running the animation
* Press "s" key to single-step animation
* The up arrow key and down array key control the
* time step used in the animation rate. Each key
* press multiplies or divides the times by a factor
* of sqrt(2).
* Press ESCAPE to exit.
*
*/
#include <math.h> // For math routines (such as sqrt & trig).
#include <stdio.h>
#include <stdlib.h> // For the "exit" function
#include <GL/glut.h> // OpenGL Graphics Utility Library
#include "SimpleAnim.h"
int RunMode = 1; // Used as a boolean (1 or 0) for "on" and "off"
// The next global variable controls the animation's state and speed.
float CurrentAngle = 0.0f; // Angle in degrees
float AnimateStep = 3.0f; // Rotation step per update
// These variables set the dimensions of the rectanglar region we wish to view.
const double Xmin = 0.0, Xmax = 3.0;
const double Ymin = 0.0, Ymax = 3.0;
// glutKeyboardFunc is called below to set this function to handle
// all "normal" key presses.
void myKeyboardFunc( unsigned char key, int x, int y )
{
switch ( key ) {
case 'r':
RunMode = 1-RunMode; // Toggle to opposite value
if ( RunMode==1 ) {
glutPostRedisplay();
}
break;
case 's':
RunMode = 1;
drawScene();
RunMode = 0;
break;
case 27: // Escape key
exit(1);
}
}
// glutSpecialFunc is called below to set this function to handle
// all "special" key presses. See glut.h for the names of
// special keys.
void mySpecialKeyFunc( int key, int x, int y )
{
switch ( key ) {
case GLUT_KEY_UP:
if ( AnimateStep < 1.0e3) { // Avoid overflow problems
AnimateStep *= sqrt(2.0); // Increase the angle increment
}
break;
case GLUT_KEY_DOWN:
if (AnimateStep>1.0e-6) { // Avoid underflow problems.
AnimateStep /= sqrt(2.0); // Decrease the angle increment
}
break;
}
}
/*
* drawScene() handles the animation and the redrawing of the
* graphics window contents.
*/
void drawScene(void)
{
// Clear the rendering window
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
if (RunMode==1) {
// Calculate animation parameters
CurrentAngle += AnimateStep;
if ( CurrentAngle > 360.0 ) {
CurrentAngle -= 360.0*floor(CurrentAngle/360.0); // Don't allow overflow
}
}
// Rotate the image
glMatrixMode( GL_MODELVIEW ); // Current matrix affects objects positions
glLoadIdentity(); // Initialize to the identity
glTranslatef( 1.5, 1.5, 0.0 ); // Translate rotation center from origin
glRotatef( CurrentAngle, 0.0, 0.0, 1.0 ); // Rotate through animation angle
glTranslatef( -1.5, -1.5, 0.0 ); // Translate rotation center to origin
// Draw three overlapping triangles of different colors
glBegin( GL_TRIANGLES );
glColor3f( 1.0, 0.0, 0.0 );
glVertex3f( 0.3, 1.0, 0.5 );
glVertex3f( 2.7, 0.85, 0.0 );
glVertex3f( 2.7, 1.15, 0.0 );
glColor3f( 0.0, 1.0, 0.0 );
glVertex3f(2.53, 0.71, 0.5 );
glVertex3f(1.46, 2.86, 0.0 );
glVertex3f(1.2, 2.71, 0.0 );
glColor3f( 0.0, 0.0, 1.0 );
glVertex3f(1.667, 2.79, 0.5);
glVertex3f(0.337, 0.786, 0.0);
glVertex3f(0.597, 0.636, 0.0);
glEnd();
// Flush the pipeline, swap the buffers
glFlush();
glutSwapBuffers();
if ( RunMode==1 ) {
glutPostRedisplay(); // Trigger an automatic redraw for animation
}
}
// Initialize OpenGL's rendering modes
void initRendering()
{
glShadeModel( GL_FLAT ); // The default value of GL_SMOOTH is usually better
glEnable( GL_DEPTH_TEST ); // Depth testing must be turned on
}
// Called when the window is resized
// w, h - width and height of the window in pixels.
void resizeWindow(int w, int h)
{
double scale, center;
double windowXmin, windowXmax, windowYmin, windowYmax;
// Define the portion of the window used for OpenGL rendering.
glViewport( 0, 0, w, h ); // View port uses whole window
// Set up the projection view matrix: orthographic projection
// Determine the min and max values for x and y that should appear in the window.
// The complication is that the aspect ratio of the window may not match the
// aspect ratio of the scene we want to view.
w = (w==0) ? 1 : w;
h = (h==0) ? 1 : h;
if ( (Xmax-Xmin)/w < (Ymax-Ymin)/h ) {
scale = ((Ymax-Ymin)/h)/((Xmax-Xmin)/w);
center = (Xmax+Xmin)/2;
windowXmin = center - (center-Xmin)*scale;
windowXmax = center + (Xmax-center)*scale;
windowYmin = Ymin;
windowYmax = Ymax;
}
else {
scale = ((Xmax-Xmin)/w)/((Ymax-Ymin)/h);
center = (Ymax+Ymin)/2;
windowYmin = center - (center-Ymin)*scale;
windowYmax = center + (Ymax-center)*scale;
windowXmin = Xmin;
windowXmax = Xmax;
}
// Now that we know the max & min values for x & y
// that should be visible in the window,
// we set up the orthographic projection.
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho( windowXmin, windowXmax, windowYmin, windowYmax, -1, 1 );
}
// Main routine
// Set up OpenGL, define the callbacks and start the main loop
int main( int argc, char** argv )
{
glutInit(&argc,argv);
// We're going to animate it, so double buffer
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
// Window position (from top corner), and size (width% and hieght)
glutInitWindowPosition( 10, 60 );
glutInitWindowSize( 360, 360 );
glutCreateWindow( "SimpleAnim" );
// Initialize OpenGL as we like it..
initRendering();
// Set up callback functions for key presses
glutKeyboardFunc( myKeyboardFunc ); // Handles "normal" ascii symbols
glutSpecialFunc( mySpecialKeyFunc ); // Handles "special" keyboard keys
// Set up the callback function for resizing windows
glutReshapeFunc( resizeWindow );
// Call this for background processing
// glutIdleFunc( myIdleFunction );
// call this whenever window needs redrawing
glutDisplayFunc( drawScene );
fprintf(stdout, "Arrow keys control speed. Press \"r\" to run, \"s\" to single step.\n");
// Start the main loop. glutMainLoop never returns.
glutMainLoop( );
return(0); // This line is never reached.
}
/*
* SimpleAnim.h
*
* Author: Samuel R. Buss
*
* Software accompanying the book
* 3D Computer Graphics: A Mathematical Introduction with OpenGL,
* by S. Buss, Cambridge University Press, 2003.
*
* Software is "as-is" and carries no warranty. It may be used without
* restriction, but if you modify it, please change the filenames to
* prevent confusion between different versions.
* Bug reports: Sam Buss, [email protected].
* Web page: http://math.ucsd.edu/~sbuss/MathCG
*/
// Function prototypes for SimpleAnim.cpp
void myKeyboardFunc( unsigned char key, int x, int y );
void mySpecialKeyFunc( int key, int x, int y );
void drawScene(void);
void initRendering();
void resizeWindow(int w, int h);
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