collideWalls

1 files changed, 49 insertions, 0 deletions

diff --git a/balls.cl b/balls.cl
index 0c235c1..9dff007 100644
--- a/balls.cl
+++ b/balls.cl
@@ -1,5 +1,24 @@
 #define RADIUS 0.15f
 
+float
+min(float a, float b) {
+	if (a < b)
+		return a;
+	return b;
+}
+
+float
+max(float a, float b) {
+	if (a > b)
+		return a;
+	return b;
+}
+
+float
+clamp(float x, float lo, float hi) {
+	return min(hi, max(x, lo));
+}
+
 __kernel void
 move(__global float2 *positions, __global float2 *velocities) {
 	size_t id;
@@ -9,6 +28,36 @@ move(__global float2 *positions, __global float2 *velocities) {
 }
 
 __kernel void
+collideWalls(__global float2 *positions, __global float2 *velocities) {
+	float2 min, max, p, v;
+	size_t id;
+
+	/* Set bounds. */
+	min.x = -1.0 + RADIUS;
+	min.y = -1.0 + RADIUS;
+	max.x = 1.0 - RADIUS;
+	max.y = 1.0 - RADIUS;
+
+	id = get_global_id(0);
+	p = positions[id];
+	v = velocities[id];
+
+	/* Check for collision with bounds. */
+	if (p.x <= min.x || p.x >= max.x) {
+		p.x = clamp(p.x, min.x, max.x);
+		v.x = -v.x;
+	}
+	if (p.y <= min.y || p.y >= max.y) {
+		p.y = clamp(p.y, min.y, max.y);
+		v.y = -v.y;
+	}
+
+	/* Write back. */
+	positions[id] = p;
+	velocities[id] = v;
+}
+
+__kernel void
 genVertices(__global float2 *positions, __global float2 *vertices) {
 	size_t ball, nsegs;
 	float2 center;