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Until PyCAM v0.4 toolpaths were simply visualized with a line. This made it impossible to distinguish a climb milling style toolpath from a conventional one. The current trunk of the development code contains a small addition that let’s you enable hints for the direction. For the sake of simplicity they are implemented as simple OpenGL cones that are added in the middle of each line.
Similarly it is now also possible to follow the direction of a 2D contour model easily. This makes it far easier to spot polygons with a wrong direction (mixing up inside/outside) as they can be accidentally generated with Inkscape.
The normals of all triangles are also marked with small lines pointing from the center of the triangle in the direction of its normal.