OpenGL GLUT bouncing ball code

Tag: OpenGL C++ Posted on 2020-04-09 22:51:06 Edited on 2020-04-09 22:51:06 Views: 16
        /*
title: OpenGL GLUT bouncing ball code
tags: 
- OpenGL
- C++
*/
#include <GL/glut.h>
#include <Math.h>

const float PI = 3.14159265f;

GLfloat ballRadius = 0.1f;
GLfloat ballX = 0.0f;
GLfloat ballY = 0.0f;
GLfloat ballXMax, ballXMin, ballYMax, ballYMin;
GLfloat xSpeed = 0.008f;
GLfloat ySpeed = 0.01f;
GLfloat xAcceleration = 0.0000f;
GLfloat yAcceleration = -0.0005f;
bool isPaused = false;
int refreshMillis = 16;

GLdouble clipAreaXLeft, clipAreaXRight, clipAreaYBottom, clipAreaYTop;

void init()
{
	glClearColor(0.0, 0.0, 0.0, 1.0);
}

void display()
{
	if (isPaused) return;
	glClear(GL_COLOR_BUFFER_BIT);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glTranslatef(ballX, ballY, 0.0f);
	glBegin(GL_TRIANGLE_FAN);
	glColor3f(1.0f, 0.0f, 0.0f);
	glVertex2f(0.0f, 0.0f);
	int numSegments = 100;
	GLfloat angle;
	for (int i = 0; i <= numSegments; i++)
	{
		angle = i * 2.0f * PI / numSegments;
		glVertex2f(cos(angle) * ballRadius, sin(angle) * ballRadius);
	}
	glEnd();

	glutSwapBuffers();
	xSpeed += xAcceleration;
	ySpeed += yAcceleration;
	ballX += xSpeed;
	ballY += ySpeed;
	if (ballX > ballXMax)
	{
		ballX = ballXMax;
		xSpeed = -xSpeed;
	}
	else if (ballX < ballXMin)
	{
		ballX = ballXMin;
		xSpeed = -xSpeed;
	}
	if (ballY > ballYMax)
	{
		ballY = ballYMax;
		ySpeed = -ySpeed;
	}
	else if (ballY < ballYMin)
	{
		ballY = ballYMin;
		ySpeed = -ySpeed;
	}
}

void reshape(GLsizei width, GLsizei height)
{
	if (height == 0) height = 1;
	GLfloat aspect = (GLfloat)width / (GLfloat)height;
	glViewport(0, 0, width, height);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	if (width >= height)
	{
		clipAreaXLeft = -1.0 * aspect;
		clipAreaXRight = 1.0 * aspect;
		clipAreaYBottom = -1.0;
		clipAreaYTop = 1.0;
	}
	else
	{
		clipAreaXLeft = -1.0;
		clipAreaXRight = 1.0;
		clipAreaYBottom = -1.0 / aspect;
		clipAreaYTop = 1.0 / aspect;
	}
	gluOrtho2D(clipAreaXLeft, clipAreaXRight, clipAreaYBottom, clipAreaYTop);
	ballXMin = clipAreaXLeft + ballRadius;
	ballXMax = clipAreaXRight - ballRadius;
	ballYMin = clipAreaYBottom + ballRadius;
	ballYMax = clipAreaYTop - ballRadius;
}

void timer(int value)
{
	glutPostRedisplay();
	glutTimerFunc(refreshMillis, timer, 0);

}

void keyboard(unsigned char key, int x, int y) {
	switch (key)
	{
	case 32:
		isPaused = !isPaused; break;
	default: break;
	}
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE);
	glutInitWindowSize(500, 500);
	glutCreateWindow("bouncing-ball");
	glutDisplayFunc(display);
	glutReshapeFunc(reshape);
	glutKeyboardFunc(keyboard);
	glutTimerFunc(0, timer, 0);
	init();
	glutMainLoop();
	return 0;
}
    

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