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Created May 15, 2020 03:46
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// Bounce.c
// Demonstrates a simple animated rectangle program with GLUT
// OpenGL SuperBible, 2nd Edition
// Richard S. Wright Jr.
#include <windows.h>
#include <gl/glut.h>
// Initial square position and size
GLfloat x1 = 100.0f;
GLfloat y1 = 150.0f;
GLsizei rsize = 50;
// 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 = 250.0f;
GLfloat windowHeight = 250.0f;
// 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(x1, y1, x1 + rsize, y1 + rsize);
// Flush drawing commands
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 (x1 > windowWidth - rsize || x1 < 0)
xstep = -xstep;
// Reverse direction when you reach top or bottom edge
if (y1 > windowHeight - rsize || y1 < 0)
ystep = -ystep;
// Check bounds. This is incase the window is made
// smaller and the rectangle is outside the new
// clipping volume
if (x1 > windowWidth - rsize)
x1 = windowWidth - rsize - 1;
if (y1 > windowHeight - rsize)
y1 = windowHeight - rsize - 1;
// Actually move the square
x1 += xstep;
y1 += ystep;
// 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(GLsizei w, GLsizei h)
{
// 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();
// Keep the square square, this time, save calculated
// width and height for later use
if (w <= h)
{
windowHeight = 250.0f*h / w;
windowWidth = 250.0f;
}
else
{
windowWidth = 250.0f*w / h;
windowHeight = 250.0f;
}
// Set the clipping volume
glOrtho(0.0f, windowWidth, 0.0f, windowHeight, 1.0f, -1.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
// Main program entry point
void main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
glutCreateWindow("Bounce");
glutDisplayFunc(RenderScene);
glutReshapeFunc(ChangeSize);
glutTimerFunc(33, TimerFunction, 1);
SetupRC();
glutMainLoop();
}
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