The algorithm that builds outlines ("silhouettes") makes an outline in 2d parametric space of the surface starting from some previously detected point where normal is orthogonal to direction of view. So, the surface is previously discretized into (m*n) sample points and some of them become starting points for future outlines.
If the surface has non-uniform parametrization and/or some local extremums of curvature, the outlines can not be built without breaks, so there are several groups of consequent outlines in this case. Unfortunately, it leads to the situation when current number of sample points becomes insufficient to build all the parts of outlines.
The idea is to detect the "holes" between already constructed parts of outlines and then complete the construction.
New auxiliary draw command for testing of HLR.
Correction according to the remarks.
Update of test case according to the developer's directive
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