This is a tool that I've written to help parameterize a polygon mesh back to format that's usable for CAD modelling.
Typically, it's used when you only have a STL file of some model and want to apply some modification to it without having to model the same object from scratch completely again. It can be used to measure features out of a STL model, build up sketches and in the future, rebuild a stack of functions to apply to the sketches to get the initial object.
Please have a look to the picture above.
Go there for a demo of this tool online.
Many of the algorithms used by this tools are made without any consideration for speed but correctness and ease of development instead. As far as I know, there isn't any open standard parametric CAD format. FreeCAD is open source, but its file format is not documented. So exporting of sketches is done in SVG right now, although you can't import them in FreeCAD.
Optimization might come later when I'm done with all the ideas of improvement of features.
The project is plugin based, so it'll likely be improved step by step.
The sketcher is using canvas (and also SVG) to draw the model to sketches. My canvas skills are limited so there might be bugs in the output drawn.
I'm planning to improve the tool by adding and fixing plugins in a rolling release fashion.