Re: [Vxl-maintainers] vgl_point_3d eps test

[Kieran O'M. <kie...@gm...>]

Unfortunately, in order to be usable introducing an argument with a
default value (presumably defaulting to 0) would require the
introduction of default values in other vgl functions which use
vgl_point_3d's coplanar function e.g. functions in vgl_intersection
and vgl_line_3d_2_points.

Introducing changes in these functions would probably suggest that a
lot of vgl functions should be updated with default eps arguments
also.

However a more serious issue if default eps arguments were introduced
would be their compatability between functions.

For example if a vgl_intersection function required an eps check of
sqrt_eps say but vgl_point_3d coplanar should only be checking against
eps directly then it is undesirable for vgl_intersection to pass on
its eps argument to vgl_point_3d.

Therefore I would like to avoid introducing a default argument. Hope
this makes sense.

Kieran

On 16/08/07, Joseph Mundy <mu...@le...> wrote:
> Sounds like a good idea to me. What about a default value for epsilon?
> Joe
>
> -----Original Message-----
> From: vxl...@li...
> [mailto:vxl...@li...] On Behalf Of
> Kieran O'Mahony
> Sent: Thursday, August 16, 2007 8:38 AM
> To: vxl...@li...
> Subject: [Vxl-maintainers] vgl_point_3d eps test
>
> Hi all,
>
> I am currently working with Ian Scott and as part of my work I am
> dealing quite a bit with parts of vxl but mainly vgl.
>
> Something that has cropped up recently is the lack of an eps test in
> the vgl_point_3d coplanar() function. At present the decision is based
> on a direct equality check with zero. Would anyone object to replacing
> this with a bounds check around zero using
> vcl_numeric_limits<Type>::epsilon() ?
>
> This should be fine for all possible template types as according to
> the C++ standard epsilon() should return 0 for any types where it
> doesn't make sense (integer etc).
>
> BTW I also noticed a couple of sign mistakes in the same function and
> have corrected them.
>
> Thanks,
> Kieran
>
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