public static Cubic <SpanF> MultiplySpanByMatrix(Cubic <SpanF> span, Matrix4x4 mat)
{
SpanAPI.WeakTODO();
// slow but accurate way
bool doAllCorners = false;
if (doAllCorners)
{
var ans = span
.Select(k => k.EachOfFromAndTo()) // seperate from and to
.EachPermutation() // generate all corner permutations
.Select(k => ToVector3(k))
.Select(k => mat.MultiplyPoint(k)) // transform by matrix
.Select(k => k.ToCubic().Select(j => SpanAPI.spanExactly(j))) // back into spans
.Aggregate((a, b) => a.Select2(b, (c, d) => SpanAPI.spanUnion(c, d))); // take union of all
return(ans);
}
// only doing the corners, ideally do all:
var cornerAM = ToVector3(span.Select(k => k.From));
var cornerBM = ToVector3(span.Select(k => k.To));
var cornerAW = mat.MultiplyPoint(cornerAM);
var cornerBW = mat.MultiplyPoint(cornerBM);
return(new Cubic <SpanF>(
SpanAPI.spanUnsorted(cornerAW.x, cornerBW.x),
SpanAPI.spanUnsorted(cornerAW.y, cornerBW.y),
SpanAPI.spanUnsorted(cornerAW.z, cornerBW.z)
));
}