[geos-devel] Precision model and predicates

[Ben Harper]

Hi,
I'm trying to use GEOS to evaluate geometric predicates while using a Precision Model that is lower than the default. It looks as though the Precision Model is only used for certain operations, and in particular ignored when evaluating the border conditions of whether lines touch each other. I've read the JTS technical docs, and they seemed to imply that this type of thing should work.

My test is to create two polygons side by side, with one touching edge. The TOUCH predicate evaluates true. I then move one polygon away by DBL_EPSILON (1e-16), and evaluate the predicate again. This time it is false. A brief step through and code search seems to reveal that the precision model is not used here.

Am I completely missing the point?

Thanks,
Ben
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/geos-devel/attachments/20090128/7a9bf03d/attachment.html