Possible mouse mapping architecture quad-mesh -> quad-mesh transformations?

Matthias Hopf mhopf at suse.de
Thu Jun 29 06:42:57 PDT 2006

On Jun 28, 06 13:17:05 +0200, Keith Packard wrote:
> So, my thought is that we construct a mapping from a quadrilateral
> decomposition of the physical screen coordinate space to a quadrilateral
> decomposition of the root window coordinate space.

What kind of coordinate interpolation should be used here? A bilinear
interpolation will not be accurate enough, if a large quadrilateral
should be used to represent a perspective projected quad.

Bilinear interpolated homogenous coordinates would suffice, of course,
but I don't know in which kind of coordinate system you are planing to

Also everyone should be aware that there could be situations, where a
correct mapping would require a dense quadrilateral field, but I assume
for all reasonable use cases (i.e. the application can still be worked
with, so that transformed mouse coordinates actually matter) the
transformation can be estimated with a much smaller number of quads.

> I think this can work for coordinate transformation; one question is
> whether we'll need a separate data structure for hit detection; at
> first glance, I think we will, but it seems like it can use another
> quad mesh region structure of some kind.

I don't think this is an issue on the API side, the server might need a
different data structure for fast hit detection. But I assume this data
can be extracted from the quad mesh.


Matthias Hopf <mhopf at suse.de>       __        __   __
Maxfeldstr. 5 / 90409 Nuernberg    (_   | |  (_   |__         mat at mshopf.de
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