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#include "balls.h"
static int clamp(int v, int lo, int hi);
static int min(int a, int b);
static int max(int a, int b);
int
iscollision(Point p1, uint r1, Point p2, uint r2) {
int dx, dy;
dx = p1.x - p2.x;
dy = p1.y - p2.y;
return (dx*dx + dy*dy) <= (r1+r2)*(r1+r2);
}
void
collideball(Ball *b1, const Ball *b2) {
Point midpoint;
Vec d, n;
double magnitude;
if (!iscollision(b1->p, b1->r, b2->p, b2->r))
return;
midpoint = divpt(addpt(b1->p, b2->p), 2);
d = Vpt(b2->p, b1->p);
b1->p = ptaddv(midpoint, vmuls(unitnorm(d), b1->r));
printf("collision (%d,%d), (%d,%d)\n", b1->p.x, b1->p.y, b2->p.x, b2->p.y);
printf("oldv: (%2.2f,%2.2f\n", b1->v.x, b1->v.y);
n = unitnorm(Vpt(b2->p, b1->p));
magnitude = 2*(vdot(b1->v, n) - vdot(b2->v, n)) / (b1->m + b2->m);
printf("n: (%2.2f,%2.2f), magnitude: %2.2f\n", n.x, n.y, magnitude);
b1->v = vsub(b1->v, vmuls(n, magnitude * b1->m));
printf("newv: (%2.2f,%2.2f)\n", b1->v.x, b1->v.y);
}
void
collidewall(Ball *b, Rectangle wall) {
wall = insetrect(wall, b->r);
if (b->p.x < wall.min.x || b->p.x > wall.max.x) {
b->p.x = clamp(b->p.x, wall.min.x, wall.max.x);
printf("clamped to %d\n", b->p.x);
b->v.x = -b->v.x;
}
if (b->p.y < wall.min.y || b->p.y > wall.max.y) {
b->p.y = clamp(b->p.y, wall.min.y, wall.max.y);
b->v.y = -b->v.y;
}
}
static int
clamp(int v, int lo, int hi) {
return min(hi, max(v, lo));
}
static int
min(int a, int b) {
return (a < b) ? a : b;
}
static int
max(int a, int b) {
return (a > b) ? a : b;
}
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