// Bounce.c // Demonstrates a simple animated rectangle program with GLUT // OpenGL SuperBible, 3rd Edition // Richard S. Wright Jr. // [email protected]#include "../../Common/OpenGLSB.h" // System and OpenGL Stuff// Initial square position and size GLfloat x = 0.0f; GLfloat y = 0.0f; GLfloat rsize = 25;// Step size in x and y directions // (number of pixels to move each time) GLfloat xstep = 1.0f; GLfloat ystep = 1.0f;// Keep track of windows changing width and height GLfloat windowWidth; GLfloat windowHeight;/////////////////////////////////////////////////////////// // Called to draw scene void RenderScene(void) { // Clear the window with current clearing color glClear(GL_COLOR_BUFFER_BIT); // Set current drawing color to red // R G B glColor3f(1.0f, 0.0f, 0.0f); // Draw a filled rectangle with current color glRectf(x, y, x + rsize, y - rsize); // Flush drawing commands and swap glutSwapBuffers(); }/////////////////////////////////////////////////////////// // Called by GLUT library when idle (window not being // resized or moved) void TimerFunction(int value) { // Reverse direction when you reach left or right edge if(x > windowWidth-rsize || x < -windowWidth) xstep = -xstep; // Reverse direction when you reach top or bottom edge if(y > windowHeight || y < -windowHeight + rsize) ystep = -ystep; // Actually move the square x += xstep; y += ystep; // Check bounds. This is in case the window is made // smaller while the rectangle is bouncing and the // rectangle suddenly finds itself outside the new // clipping volume if(x > (windowWidth-rsize + xstep)) x = windowWidth-rsize-1; else if(x < -(windowWidth + xstep)) x = -windowWidth -1; if(y > (windowHeight + ystep)) y = windowHeight-1; else if(y < -(windowHeight - rsize + ystep)) y = -windowHeight + rsize - 1; // Redraw the scene with new coordinates glutPostRedisplay(); glutTimerFunc(33,TimerFunction, 1); } /////////////////////////////////////////////////////////// // Setup the rendering state void SetupRC(void) { // Set clear color to blue glClearColor(0.0f, 0.0f, 1.0f, 1.0f); } /////////////////////////////////////////////////////////// // Called by GLUT library when the window has chanaged size void ChangeSize(int w, int h) { GLfloat aspectRatio; // Prevent a divide by zero if(h == 0) h = 1;
// Demonstrates a simple animated rectangle program with GLUT
// OpenGL SuperBible, 3rd Edition
// Richard S. Wright Jr.
// [email protected]#include "../../Common/OpenGLSB.h" // System and OpenGL Stuff// Initial square position and size
GLfloat x = 0.0f;
GLfloat y = 0.0f;
GLfloat rsize = 25;// Step size in x and y directions
// (number of pixels to move each time)
GLfloat xstep = 1.0f;
GLfloat ystep = 1.0f;// Keep track of windows changing width and height
GLfloat windowWidth;
GLfloat windowHeight;///////////////////////////////////////////////////////////
// Called to draw scene
void RenderScene(void)
{
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT); // Set current drawing color to red
// R G B
glColor3f(1.0f, 0.0f, 0.0f); // Draw a filled rectangle with current color
glRectf(x, y, x + rsize, y - rsize); // Flush drawing commands and swap
glutSwapBuffers();
}///////////////////////////////////////////////////////////
// Called by GLUT library when idle (window not being
// resized or moved)
void TimerFunction(int value)
{
// Reverse direction when you reach left or right edge
if(x > windowWidth-rsize || x < -windowWidth)
xstep = -xstep; // Reverse direction when you reach top or bottom edge
if(y > windowHeight || y < -windowHeight + rsize)
ystep = -ystep; // Actually move the square
x += xstep;
y += ystep; // Check bounds. This is in case the window is made
// smaller while the rectangle is bouncing and the
// rectangle suddenly finds itself outside the new
// clipping volume
if(x > (windowWidth-rsize + xstep))
x = windowWidth-rsize-1;
else if(x < -(windowWidth + xstep))
x = -windowWidth -1; if(y > (windowHeight + ystep))
y = windowHeight-1;
else if(y < -(windowHeight - rsize + ystep))
y = -windowHeight + rsize - 1; // Redraw the scene with new coordinates
glutPostRedisplay();
glutTimerFunc(33,TimerFunction, 1);
}
///////////////////////////////////////////////////////////
// Setup the rendering state
void SetupRC(void)
{
// Set clear color to blue
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
}
///////////////////////////////////////////////////////////
// Called by GLUT library when the window has chanaged size
void ChangeSize(int w, int h)
{
GLfloat aspectRatio; // Prevent a divide by zero
if(h == 0)
h = 1;
// Set Viewport to window dimensions
glViewport(0, 0, w, h); // Reset coordinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity(); // Establish clipping volume (left, right, bottom, top, near, far)
aspectRatio = (GLfloat)w / (GLfloat)h;
if (w <= h)
{
windowWidth = 100;
windowHeight = 100 / aspectRatio;
glOrtho (-100.0, 100.0, -windowHeight, windowHeight, 1.0, -1.0);
}
else
{
windowWidth = 100 * aspectRatio;
windowHeight = 100;
glOrtho (-windowWidth, windowWidth, -100.0, 100.0, 1.0, -1.0);
} glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}///////////////////////////////////////////////////////////
// Main program entry point
int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(800,600);
glutCreateWindow("Bounce");
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);
glutTimerFunc(33, TimerFunction, 1); SetupRC(); glutMainLoop();
return 0;
}