[Smtk-developers] polygon progress

[David Thompson]

Hi all,

FYI: model, vertex, and edge creation operations are done and tested in SMTK for polygonal models but not merged yet. (It is in my github account on a branch named polygon.) A screenshot of the test dataset is attached and shows how a few odd conditions are handled:

+ the 4 vertices forming a small square near the center of the screenshot are placed into the model as model vertices;
+ the lower left shows how a request for 1 edge with 4 input points then gets turned into 4 edges due to self-intersection and contact with a pre-existing model vertex. 3 additional model vertices are created.
+ the bottom right shows how a request for 1 periodic edge with 5 input points is turned into 2 model edges. The model vertex in the output is not an input point; it is where 2 segments intersect.
+ the top left square shows a model edge with 5 input points and no model vertices.

There are some caveats:

+ the code used to enforce CCW-ordering of edges incident to each vertex is not numerically robust; it uses floating-point math and does not detect overflows or integer truncation due to the approximation of sqrt.
+ no GUI is provided for inserting points

The remaining operations to implement are (in rough order of priority):

+ create all possible, non-existent faces from a set of edges.
+ split an edge
+ merge edges
+ create a face given outer (and optionally inner) loops
+ move vertices (note that this could be very painful to do robustly when edges are attached).
+ booleans via boost.polygon
+ voronoi diagrams via boost.polygon

	David

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