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| = Notes about GeoPainter =
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| == Concepts ==
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| Horizon is a spherical projection concept to decide if a point is on the viewer's side or the other.
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| It is NOT dependent on viewport visibility
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| Dateline is a repeatX issue, so that a line crossing the dateline does not lead to a tear the whole map wide
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| Pole is an issue for projections which cannot draw it as a point (or even not at all)
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| Projection Drawing depends on tessellation
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| Tessellation is a geodetic issue, determining how to connect points. Options:
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| NoTessellation: straight screen coordinates lines between projected points
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| Tessellate: great circle line between projected points
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| needs horizon and dateline check
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| FollowLatitude: special case when latitude is same, walk on the latitude circle
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| do we need rhumb line (line of constant compass course)??
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| Need to keep in mind that tessellating must keep polygons that still allow fill.
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| == Current code ==
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| - systematically looks for poles and datelines, splitting the polyline into ones which don't cross idl or pole
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| - looking for datelines is a recursive calculus to identify latitude at which the idl is crossed
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| - iterates all points, determines
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| - if horizon is crossed
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| - if and which tessellation is needed
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| - adds points to one QVector<QPointF>
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| == Complications ==
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| - looking for dateline is not necessary for Spherical, very hard for NoTessellation (screen vs Geo space)
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| - because of repeatX we calculate all possible points depending on viewport radius, then let painter frame down to visible viewport
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