[Vxl-maintainers] vgl_intersection - should be undone?

[Ian S. <ian...@st...>]

Gamze, and vxl-maintainers.

We have come across other problems with this mod, and would like to 
suggest that it be undone, while the issues are resolved.


We use vgl_box_[23]d<int> a lot. It had an intersection function - doing 
the obvious thing. When the box intersections were moved into the 
vgl_intersection.*, no <int> template instantiation for vgl_intersection 
was created.

When we added the <int> template instantiation we realised that now 
vgl_intersection needs vgl_distance, and hence vgl_distance <int> 
template instantiations. However it doesn't really make sense to 
instantiate vgl_distance with <int>. We still haven't tracked down all 
the missing <int> instantiations. In particular it would require the 
<int> instantiation of things like vgl_homg_line, etc.

We are also not clear about why vgl_instantiation has to be in vgl_algo. 
All the intersection methods we use are simple, and forcing us to link 
into vgl_algo adds unnecessary cost to the link time.

With the previously identified violation of the One Definition Rule, 
perhaps this mod should be backed out until it is more thoroughly tested?

One potential fix is to split the instantiation macro into two bits - 
one bit for <int> compatible functions, and one macro for <float>-only 
functions.

Ian Scott.

Gamze Tunali wrote:
> Hi,
> 
> This is a heads up for the new files
> "vgl_intersection.h" and "vgl_intersection.txx" under
> vgl. Like vgl_distance and vgl_closest_point, we
> thought that gathering intersection methods into a
> file will help to find the available methods while
> doing intersection easily. The intersection methods in
> various vgl classes are still there but there is a
> deprecated warning on them. Please start to use
> intersection methods from vgl_intersection.h. I am
> planning to delete the deprecated version after a
> while, when vxl users are aware of the new addition.
> 
> There are also intersection methods in
> vgl/algo/vgl_homg_operators. They may be moved into a
> vgl/algo/vgl_homg_intersection as a future to do. I
> noticed that the intersection of a vector of planes
> does not have an assertion on the number of planes.
> But it seems like it should be at least >=3 since the
> result is a vgl_homg_point_3d. Is it a bug or is there
> an explanation that I could not deduce.
> 
> Gamze Tunali
> LEMS, Brown University
> 
> 
> 
> 
> 
>  
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