refactor collisions

3 files changed, 78 insertions, 66 deletions

diff --git a/balls.c b/balls.c
index 92f1f2d..d742d67 100644
--- a/balls.c
+++ b/balls.c
@@ -1,6 +1,5 @@
 #include "balls.h"
 
-#include <stdio.h>
 #include <thread.h>
 #include <mouse.h>
 #include <keyboard.h>
@@ -44,8 +43,8 @@ typedef struct {
 	int nothers; /* number of other balls */
 } BallArg;
 
-int ballcolors[] = { DRed, DGreen, DBlue };
-Rectangle bounds = {{PAD, PAD}, {PAD+WIDTH, PAD+HEIGHT}};
+static int ballcolors[] = { DRed, DGreen, DBlue };
+static Rectangle bounds = {{PAD, PAD}, {PAD+WIDTH, PAD+HEIGHT}};
 
 int init(char *label, Mousectl **mctl, Keyboardctl **kctl);
 void spawnball(void);
@@ -60,9 +59,6 @@ int randint(int lo, int hi);
 void ball(void *arg);
 Image *alloccircle(int fg, int bg);
 void drawcircle(Image *m, Point pos);
-int clamp(int v, int lo, int hi);
-int min(int a, int b);
-int max(int a, int b);
 void broadcast(Point p, Channel *cs[], int n);
 void frametick(void *arg);
 
@@ -277,73 +273,43 @@ randint(int lo, int hi) {
 void
 ball(void *arg) {
 	BallArg *barg;
-	Point p, oldp;
-	Vec v;
-	int m;
+	Ball b;
 	Image *fill, *erase;
+	Point oldpos;
 	int i;
 	Ball other;
-	Point midpoint;
-	Vec d, n;
-	double magnitude;
 	int t;
 
 	barg = (BallArg *) arg;
-	p = oldp = barg->b.p;
-	v = barg->b.v;
-	m = barg->b.m;
+	b = (Ball) barg->b;
 
 	fill = alloccircle(barg->color, DTransparent);
 	erase = alloccircle(BG, DTransparent);
 	if (fill == nil ||erase == nil)
 		sysfatal("failed to allocate image");
 
+	oldpos = b.p;
 	for (;;) {
-		v.y += G;
+		b.v.y += G;
 
-		p = ptaddv(p, v);
+		b.p = ptaddv(b.p, b.v);
 
-		printf("(%d,%d) %f %f\n", p.x, p.y, v.x, v.y);
+		printf("(%d,%d) %f %f\n", b.p.x, b.p.y, b.v.x, b.v.y);
 
-		broadcast(p, barg->out, barg->nothers);
+		broadcast(b.p, barg->out, barg->nothers);
 
 		/* check for ball collision */
 		for (i = 0; i < barg->nothers; i++) {
 			recv(barg->in[i], &other);
-			if (iscollision(p, other.p)) {
-				midpoint = divpt(addpt(p, other.p), 2);
-				d = Vpt(other.p, p);
-				p = ptaddv(midpoint, vmuls(unitnorm(d), RADIUS));
-
-				printf("collision (%d,%d), (%d,%d)\n", p.x, p.y, other.p.x, other.p.y);
-
-				printf("oldv: (%2.2f,%2.2f\n", v.x, v.y);
-
-				n = unitnorm(Vpt(other.p, p));
-				magnitude = 2*(vdot(v, n) - vdot(other.v, n)) / (m + other.m);
-
-				printf("n: (%2.2f,%2.2f), magnitude: %2.2f\n", n.x, n.y, magnitude);
-
-				v = vsub(v, vmuls(n, magnitude * m));
-
-				printf("newv: (%2.2f,%2.2f)\n", v.x, v.y);
-			}
+			collideball(&b, &other);
 		}		
 
-		/* check for wall collision */
-		if (p.x < bounds.min.x+RADIUS || p.x > bounds.max.x-RADIUS) {
-			p.x = clamp(p.x, bounds.min.x+RADIUS, bounds.max.x-RADIUS);
-			printf("clamped to %d\n", p.x);
-			v.x = -v.x;
-		}
-		if (p.y < bounds.min.y+RADIUS || p.y > bounds.max.y-RADIUS) {
-			p.y = clamp(p.y, bounds.min.y+RADIUS, bounds.max.y-RADIUS);
-			v.y = -v.y;
-		}		
+		collidewall(&b, bounds);
+
 		recv(barg->frametick, &t);
-		drawcircle(erase, oldp);
-		drawcircle(fill, p);
-		oldp = p;
+		drawcircle(erase, oldpos);
+		drawcircle(fill, b.p);
+		oldpos = b.p;
 
 	}	
 }
@@ -372,21 +338,6 @@ drawcircle(Image *m, Point pos) {
 	draw(screen, rectaddpt(bounds, subpt(pos, Pt(RADIUS, RADIUS))), m, nil, ZP);
 }
 
-int
-clamp(int v, int lo, int hi) {
-	return min(hi, max(v, lo));
-}
-
-int
-min(int a, int b) {
-	return (a < b) ? a : b;
-}
-
-int
-max(int a, int b) {
-	return (a > b) ? a : b;
-}
-
 void
 broadcast(Point p, Channel *cs[], int n) {
 	while (n-- > 0)
diff --git a/balls.h b/balls.h
index 8e66ae0..69adde9 100644
--- a/balls.h
+++ b/balls.h
@@ -1,5 +1,6 @@
 #include <u.h>
 #include <libc.h>
+#include <stdio.h>
 #include <draw.h>
 #include <cursor.h>
 
@@ -31,4 +32,6 @@ Point ptaddv(Point p, Vec v);
 Vec V(double x, double y);
 Vec Vpt(Point p, Point q);
 
-int iscollision(Point p, Point q);
\ No newline at end of file
+int iscollision(Point p, Point q);
+void collideball(Ball *b1, const Ball *b2);
+void collidewall(Ball *b, Rectangle wall);
diff --git a/collision.c b/collision.c
index 3890f66..1fa083b 100644
--- a/collision.c
+++ b/collision.c
@@ -1,5 +1,9 @@
 #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 p, Point q) {
 	int dx, dy;
@@ -8,3 +12,57 @@ iscollision(Point p, Point q) {
 	dy = p.y - q.y;
 	return (dx*dx + dy*dy) <= 4*RADIUS*RADIUS;
 }
+
+void
+collideball(Ball *b1, const Ball *b2) {
+	Point midpoint;
+	Vec d, n;
+	double magnitude;
+
+	if (!iscollision(b1->p, b2->p))
+		return;
+	midpoint = divpt(addpt(b1->p, b2->p), 2);
+	d = Vpt(b2->p, b1->p);
+	b1->p = ptaddv(midpoint, vmuls(unitnorm(d), RADIUS));
+
+	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) {
+	if (b->p.x < wall.min.x+RADIUS || b->p.x > wall.max.x-RADIUS) {
+		b->p.x = clamp(b->p.x, wall.min.x+RADIUS, wall.max.x-RADIUS);
+		printf("clamped to %d\n", b->p.x);
+		b->v.x = -b->v.x;
+	}
+	if (b->p.y < wall.min.y+RADIUS || b->p.y > wall.max.y-RADIUS) {
+		b->p.y = clamp(b->p.y, wall.min.y+RADIUS, wall.max.y-RADIUS);
+		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;
+}
\ No newline at end of file