private bool DoExternalNear(out TinyStructList<ContactData> contactList)
{
Vector3 closestA, closestB;
//Don't bother trying to do any clever caching. The continually transforming simplex makes it very rarely useful.
//TODO: Initialize the simplex of the GJK method using the 'true' center of the triangle.
//If left unmodified, the simplex that is used in GJK will just be a point at 0,0,0, which of course is at the origin.
//This causes an instant-out, always. Not good!
//By giving the contributing simplex the average centroid, it has a better guess.
Vector3 triangleCentroid;
Vector3.Add(ref triangle.vA, ref triangle.vB, out triangleCentroid);
Vector3.Add(ref triangleCentroid, ref triangle.vC, out triangleCentroid);
Vector3.Multiply(ref triangleCentroid, .33333333f, out triangleCentroid);
var initialSimplex = new CachedSimplex { State = SimplexState.Point, LocalSimplexB = { A = triangleCentroid } };
if (GJKToolbox.GetClosestPoints(convex, triangle, ref Toolbox.RigidIdentity, ref Toolbox.RigidIdentity, ref initialSimplex, out closestA, out closestB))
{
state = CollisionState.Deep;
return DoDeepContact(out contactList);
}
Vector3 displacement;
Vector3.Subtract(ref closestB, ref closestA, out displacement);
float distanceSquared = displacement.LengthSquared();
float margin = convex.collisionMargin + triangle.collisionMargin;
contactList = new TinyStructList<ContactData>();
if (distanceSquared < margin * margin)
{
//Try to generate a contact.
var contact = new ContactData();
//Determine if the normal points in the appropriate direction given the sidedness of the triangle.
if (triangle.sidedness != TriangleSidedness.DoubleSided)
{
Vector3 triangleNormal, ab, ac;
Vector3.Subtract(ref triangle.vB, ref triangle.vA, out ab);
Vector3.Subtract(ref triangle.vC, ref triangle.vA, out ac);
Vector3.Cross(ref ab, ref ac, out triangleNormal);
float dot;
Vector3.Dot(ref triangleNormal, ref displacement, out dot);
if (triangle.sidedness == TriangleSidedness.Clockwise && dot > 0)
return false;
if (triangle.sidedness == TriangleSidedness.Counterclockwise && dot < 0)
return false;
}
//Displacement is from A to B. point = A + t * AB, where t = marginA / margin.
if (margin > Toolbox.Epsilon) //This can be zero! It would cause a NaN if unprotected.
Vector3.Multiply(ref displacement, convex.collisionMargin / margin, out contact.Position); //t * AB
else contact.Position = new Vector3();
Vector3.Add(ref closestA, ref contact.Position, out contact.Position); //A + t * AB.
contact.Normal = displacement;
float distance = (float)Math.Sqrt(distanceSquared);
Vector3.Divide(ref contact.Normal, distance, out contact.Normal);
contact.PenetrationDepth = margin - distance;
contactList.Add(ref contact);
TryToEscape(ref contact.Position);
return true;
}
//Too far to make a contact- move back to separation.
state = CollisionState.ExternalSeparated;
return false;
}
