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#include "balls.h"
#define VMAX_INIT 0.1
/* max initial velocity [m/frame] */
#define RMIN 0.05
#define RMAX 0.10
/* min/max radius [m] */
#define DENSITY 1500.0
/* density of ball [kg/m^3] */
#define G (9.81/FPS/FPS)
/* acceleration of gravity [m/(frame*frame)] */
enum {
WIDTH = 800,
HEIGHT = 600,
KEY_QUIT = 'q',
CIRCLE_SEGS = 32,
FPS = 60,
MS_PER_S = 1000,
FRAME_TIME_MS = MS_PER_S / FPS,
NBALLS_DEFAULT = 3,
};
void keyboard(unsigned char key, int x, int y);
void display(void);
void drawBackground(void);
void drawCircle(double radius, Point p, Color color);
void reshape(int w, int h);
vector<Ball *> makeBalls(int n);
vector<Point> noOverlapCircles(unsigned int n);
double mass(double radius);
double volume(double radius);
void animate(int v);
Color randColor(void);
const static Rectangle bounds = {{-1.5, -1.0}, {1.5, 1.0}};
vector<Ball *> balls;
vector<vector<Collision>> collisionPartition;
int
main(int argc, char *argv[]) {
int nballs;
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowSize(WIDTH, HEIGHT);
glutCreateWindow("Balls");
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
nballs = NBALLS_DEFAULT;
if (argc > 1) {
if (sscanf(argv[1], "%d", &nballs) != 1 || nballs < 1) {
printf("usage: balls [number of balls]\n");
return 1;
}
}
balls = makeBalls(nballs);
collisionPartition = partitionCollisions(balls);
glutTimerFunc(FRAME_TIME_MS, animate, 0);
glutMainLoop();
return 1;
}
void
keyboard(unsigned char key, int x, int y) {
if (key == KEY_QUIT)
glutDestroyWindow(glutGetWindow());
}
void
display(void) {
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);
drawBackground();
/* TODO: parallel */
for (const Ball *b : balls)
drawCircle(b->r, b->p, b->color);
glutSwapBuffers();
}
void
drawBackground(void) {
glColor3f(1, 1, 1);
glBegin(GL_QUADS);
glVertex2f(bounds.min.x, bounds.min.y);
glVertex2f(bounds.max.x, bounds.min.y);
glVertex2f(bounds.max.x, bounds.max.y);
glVertex2f(bounds.min.x, bounds.max.y);
glEnd();
}
void
drawCircle(double radius, Point p, Color color) {
int i;
double theta, x, y;
glColor3f(color.r, color.g, color.b);
glBegin(GL_TRIANGLE_FAN);
glVertex2f(p.x, p.y);
for (i = 0; i <= CIRCLE_SEGS; i++) {
theta = 2.0 * M_PI * i / CIRCLE_SEGS;
x = radius * cosf(theta);
y = radius * sinf(theta);
glVertex2f(x+p.x, y+p.y);
}
glEnd();
}
void
reshape(int w, int h) {
double ratio;
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
ratio = (double) w / (double) h;
if (ratio >= 1.0)
glOrtho(-ratio, ratio, -1, 1, -1, 1);
else
glOrtho(-1, 1, -1.0/ratio, 1.0/ratio, -1, 1);
glMatrixMode(GL_MODELVIEW);
}
vector<Ball *>
makeBalls(int n) {
size_t i;
vector<Point> positions = noOverlapCircles(n);
vector<Ball *> balls(n);
/* TODO: parallel */
for(i = 0; i < balls.size(); i++) {
cout << "Creating ball " << i << "\n";
if ((balls[i] = (Ball *) malloc(sizeof(Ball))) == NULL) {
cerr << "failed to allocate ball\n";
while (i-- > 0)
free(balls[i]);
exit(1);
}
balls[i]->p = positions[i];
balls[i]->v.x = randDouble(-VMAX_INIT, VMAX_INIT);
balls[i]->v.y = randDouble(-VMAX_INIT, VMAX_INIT);
balls[i]->r = randDouble(RMIN, RMAX);
balls[i]->m = mass(balls[i]->r);
balls[i]->color = randColor();
};
return balls;
}
/* return n-length vector of positions of non-overlapping circles with radius RMAX within the bounds */
vector<Point>
noOverlapCircles(unsigned int n) {
vector<Point> ps(n);
Rectangle r;
unsigned int i, j;
r = insetRect(bounds, RMAX);
for (i = 0; i < n; i++) {
cout << "Create non-overlapping circle " << i << "\n";
ps[i] = randPtInRect(r);
for (j = 0; j < i; j++) /* TODO: parallel reduce */
if (isCollision(ps[j], RMAX, ps[i], RMAX))
break;
if (j < i) { /* overlapping */
i--;
continue;
}
}
return ps;
}
/* mass [kg] of ball as function of radius [m] */
double
mass(double radius) {
return volume(radius) * DENSITY;
}
/* volume [m^3] of ball as function of radius [m] */
double
volume(double radius) {
return 4.0 * M_PI * radius*radius*radius / 3.0;
}
void
animate(int v) {
/* Update position. */
parallel_for(size_t(0), balls.size(), [] (size_t i) {
balls[i]->v.y -=G;
balls[i]->p = ptAddVec(balls[i]->p, balls[i]->v);
});
/* Collide with balls. */
for (vector<Collision> cell : collisionPartition) {
parallel_for(size_t(0), cell.size(), [cell] (size_t i) {
collideBall(cell[i].b1, cell[i].b2);
});
}
/* Collide with walls. */
parallel_for(size_t(0), balls.size(), [] (size_t i) {
collideWall(balls[i], bounds);
});
display();
glutTimerFunc(FRAME_TIME_MS, animate, 0);
}
double
randDouble(double lo, double hi) {
double r, diff;
static int isInitialized = 0;
if (!isInitialized) { /* first call */
srand(time(0));
isInitialized = 1;
}
r = (double) rand() / (double) RAND_MAX;
diff = hi - lo;
return lo + r*diff;
}
Color
randColor(void) {
Color color;
color.r = randDouble(0, 1);
color.g = randDouble(0, 1);
color.b = randDouble(0, 1);
return color;
}
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