public override void GetBoundingBox(ref RigidTransform shapeTransform, out BoundingBox boundingBox)
{
#if !WINDOWS
boundingBox = new BoundingBox();
#endif
Matrix3x3 o;
Matrix3x3.CreateFromQuaternion(ref shapeTransform.Orientation, out o);
//Sample the local directions from the orientation matrix, implicitly transposed.
//Notice only three directions are used. Due to box symmetry, 'left' is just -right.
var right = new Vector3(Math.Sign(o.M11) * halfWidth, Math.Sign(o.M21) * halfHeight, Math.Sign(o.M31) * halfLength);
var up = new Vector3(Math.Sign(o.M12) * halfWidth, Math.Sign(o.M22) * halfHeight, Math.Sign(o.M32) * halfLength);
var backward = new Vector3(Math.Sign(o.M13) * halfWidth, Math.Sign(o.M23) * halfHeight, Math.Sign(o.M33) * halfLength);
Matrix3x3.Transform(ref right, ref o, out right);
Matrix3x3.Transform(ref up, ref o, out up);
Matrix3x3.Transform(ref backward, ref o, out backward);
//These right/up/backward represent the extreme points in world space along the world space axes.
boundingBox.Max.X = shapeTransform.Position.X + right.X;
boundingBox.Max.Y = shapeTransform.Position.Y + up.Y;
boundingBox.Max.Z = shapeTransform.Position.Z + backward.Z;
boundingBox.Min.X = shapeTransform.Position.X - right.X;
boundingBox.Min.Y = shapeTransform.Position.Y - up.Y;
boundingBox.Min.Z = shapeTransform.Position.Z - backward.Z;
}
