added a free fall animation example

OpenGL-Free-Fall-Animation.cpp

@@ -0,0 +1,71 @@
+#include <iostream>
+#include <cmath>
+#include <gl/glut.h>
+
+void init() {
+	glClearColor(1.0, 1.0, 1.0, 0.0);
+	glMatrixMode(GL_PROJECTION);
+	glLoadIdentity();
+	glPointSize(4.0);
+	glColor3f(0.0f, 0.0f, 0.0f);
+	gluOrtho2D(0.0, 640.0, 0.0, 480.0);
+}
+
+typedef struct {
+	double x;
+	double y;
+} Point;
+
+Point p1 = {320.0, 480.0};
+Point p2 = {340.0, 480.0};
+
+double time1 = 0.0;
+double time2 = 0.0;
+
+void calc() {
+	time1 += 0.1;
+	time2 += 0.1;
+
+	p1.y = (-0.5*9.8)*(time1*time1)+0+480;
+	p2.y = (-0.5*1.6)*(time2*time2)+0+480;
+
+	if(p1.y < 0.0) {
+		p1.y = 480;
+		time1 = 0;
+	}
+	if(p2.y < 0.0) {
+		p2.y = 480;
+		time2 = 0;
+	}
+}
+
+void display() {
+	calc();
+	glClear(GL_COLOR_BUFFER_BIT);
+	glBegin(GL_POINTS);
+		glColor3f(0.0f, 0.0f, 1.0f);
+		glVertex2d(p1.x, p1.y);
+
+		glColor3f(0.0f, 1.0f, 0.0f);
+		glVertex2d(p2.x, p2.y);
+	glEnd();
+	glFlush();
+}
+
+void Timer(int value) {
+	glutTimerFunc(1000 / 60, Timer, value);
+	glutPostRedisplay();
+}
+
+int main(int argc, char** argv) {
+	glutInit(&argc, argv);
+	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
+	glutInitWindowPosition(200, 200);
+	glutInitWindowSize(640, 480);
+	glutCreateWindow("OpenGL");
+	init();
+	Timer(0);
+	glutDisplayFunc(display);
+	glutMainLoop();
+	return 0;
+}