protected override bool TestCollisionVsAABB(AABB_2D other, out Collision collision)
{
collision = null;
// if distance between centers is greater than half widths they're not colliding
// component wise check
// 1. store abs(distance) on x, y
// 2. store width on x, y
// 3. return if distance is less than width
Vector2 ourCenter = particle.position, otherCenter = other.particle.position;
Vector2 dist = ourCenter - otherCenter;
dist.x = Mathf.Abs(dist.x);
dist.y = Mathf.Abs(dist.y);
Vector2 sumHalfWidths = halfWidths + other.halfWidths;
return(dist.x < sumHalfWidths.x && dist.y < sumHalfWidths.y);
}
protected override bool TestCollisionVsAABB(AABB_2D other, out Collision collision)
{
collision = null;
// find closest point to the circle on the box: clamp the (center - min) and (center - max)
// circle point collision test using closest point
Vector2 point, otherMin, otherMax, delta;
otherMin = other.particle.position - other.halfWidths;
otherMax = other.particle.position + other.halfWidths;
// find the closest point on the aabb
point.x = Mathf.Clamp(particle.position.x, otherMin.x, otherMax.x);
point.y = Mathf.Clamp(particle.position.y, otherMin.y, otherMax.y);
delta = particle.position - point;
bool colliding = delta.sqrMagnitude < radius * radius;
if (colliding)
{
collision = new Collision();
Vector2 relativeVelocity = particle.velocity - other.particle.velocity;
Vector2 relativePosition = particle.position - other.particle.position;
// 7.1.1 closing velocity
collision.closingVelocity = Vector3.Dot(relativeVelocity, relativePosition.normalized);
// assuming one point of contact
collision.contact[0].normal = delta.normalized;
collision.contact[0].point = point;
collision.contact[0].restitution = .5f;
collision.contact[0].penetrationDepth = radius - delta.magnitude;
collision.a = this;
collision.b = other;
collision.status = colliding;
collision.contactCount = 1;
}
// point collision with circle test
return(colliding);
}
protected override bool TestCollisionVsAABB(AABB_2D other, out Collision collision)
{
return(CollisionHull2D.TestCollision(other, this, out collision));
}
protected abstract bool TestCollisionVsAABB(AABB_2D other, out Collision collision);