[eigen] Transform products

[Hauke Heibel <hauke.heibel@xxxxxxxxxxxxxx>]

Ok, I am starting a new thread. The other one was way too long.

I started with the RHS product refactoring. Everything went well,
until I hit the case, where the RHS is a DiagonalMatrix. The patch is
attached but I will anyways past the most important piece of code over
here because it is hard to find in the diff.

The function causing troubles is ei_transform_right_product_impl::run
for Affine and Isometry. I tried to make a one fits all implementation
and in theory, it works well. Even the inlining on MSVC seems to be
working for fixed size types. For DiagonalMatrix, I am hitting the
issue, that there is now way to extract a block.

Here is how I tried to implement run:

  EIGEN_STRONG_INLINE static ResultType run(const
Transform<Scalar,Dim,Mode>& T, const Other& other)
  {
    EIGEN_STATIC_ASSERT(OtherRows==Dim || OtherRows==HDim,
YOU_MIXED_MATRICES_OF_DIFFERENT_SIZES);

    typedef Block<ResultType, Dim, OtherCols> TopLeftLhs;
    typedef Block<Other, Dim, OtherCols>      TopLeftRhs;

    ResultType res(other.rows(),other.cols());

    TopLeftLhs(res, 0, 0, Dim, other.cols()) =
      ( T.linear() * TopLeftRhs(other, 0, 0, Dim, other.cols()) ).colwise() +
        T.translation();

    // This is a hack to circumvent the fact that DiagonalMatrix does
not expose ::row(int)
    // In fact, the code below will not even be used in release mode,
but it will still be compiled.
    if (OtherRows==HDim)
      Block<ResultType, 1, OtherCols>(res,0,0,1,other.cols()) =
      Block<Other, 1, OtherCols>(other.derived(),0,0,1,other.cols());

    return res;
  }

I used Block in the end, because row() does not exist for
DiagonalMatrix. Any Ideas? I would be too sad, if I were required to
write a specialization just because of this since in general, the if
clause is already removed by the compiler -- though it is still
compiled.

On the other hand side, who want to do something like this because now
everything on the RHS is interpreted as points. If the RHS is 3x3 it
is not any more interpreted as [S 0; 0 1]. The correct move would be

A.linear() *= S;

and even this works

A * (S * pts_33)

though this does not

(A * S) * pts_33

I could even go back to row() instead of block().

I am pausing the patching for now, until I get feedback.

- Hauke

Attachment: geo_prod.patch
Description: Binary data

Attachment: main.cpp
Description: Binary data