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Elasticity and Edge Normal

In this section I discuss two important settings which are applied on edges. Both them are applied when the user is changing only one of the two sides of an edge (because one of the two vertices is selected or active and the other one is not)

Elasticity

Elasticity allows you to control how edges react when only one of their vertices is transformed. Usually drawing applications are based on the simple rule that handles should follow their vertices while moving, keeping their relative position with them.

Curved Poly allows you to choose among 4 different, alternative, behaviours.

Clayish: this means that the edge is not elastic. You will not perceive any particular elastic behaviour in Clayish mode. The edge handles will follow their vertices while moving, keeping constant their relative position.
Proportional: while moving one of the edge vertices, the relative position of both handles will scale according to the new distance between the edge vertices. The surface will look like inflating or deflating while you move vertices. Note: Proportional is the default value in almost all edges of all Primitives model available with this plugin. I have made this choice because it is the elastic response with the maximum impact on the user experience.
Elliptic: similar to proportional, but it takes into account the orientation of the edge on both sides. This is designed to make the elliptic edges keep elliptic during vertices transforms, but will have a coherent effect on edges not having an elliptic edge.
Elastic: the edge will behave like a spring, stretching when the vertices are outdistanced or flexing when you move the vertices closer one to the other.

Now you can try all the settings during any shaping process: pressing any of the four buttons will make the settings applied on your transform (the one you are working on), so that you see how each elasticity mode will affect your last transform and you can switch to the one which looks better for you. This works both in Selection Operator or Pointings Operator. Previously this was possible only by Undoing the transform, changing the setting, and reworking the transform again.

Edge Normal

Each curved edge has as a Normal vector assigned to its center. This normal may be used by the Interpolation/Filling Algorithms to correct the orientation of polygons across the edge, so it's very important that you understand what you can do to correct its orientation.

Usually this normal should change each time something is changing within the edge. There are three situations:

when using Selection Operator and both the extremes of an edge are selected: in this case, the normal is rotated of the same amount applied to the parts of the edge, so it should always be correct.
when using Selection Operator and only one extreme of an edge is selected, or when using Pointings Operator for edges affected by the active element only on one side: in all this cases, the normal is supposed to change. Curved Poly will recalculate it automatically, overwriting any previous settings, with one of the available formulas.
When using Pointings Operator with an edge active: you have many options here to manually fix the edge normal for that edge. Note that any assignment done here may be overwritten at a second time by automatic procedures (so if you need to manually correct an edge normal, that should be one of your last actions on the model).

The way in which automatic settings for edge normals are applied has been significantly improved. Now if you have made a custom editing normal (with Pointings Operator), some of the functions (Edge Normal and Axis Normal to be precise) will try to keep your settings. You can use the Update Selected Edges Normals button to force a reset of all selected normals (this is available only in Selection Mode).

There are three procedures available for automatic edge normal evaluation:

Basic Edge Normal: an algorithm which takes into accounts only the shape of the Edge and the two editing normals on the two extremes vertices. It can be assigned as the algorithm used when Curved Poly need to update an edge normal. It is, indeed, by default.
Axis Normal: an algorithm which takes into accounts the shape of the Edge, the two editing normals on the two extremes vertices and also the direction of other edges nearby the extremes. Such direction is called the Axis. Axis Normal is more correct to use in situation where there are sharp angles between edges . It can be assigned as the algorithm used when Curved Poly need to update an edge normal.
Balance (or Sphere) Normal (new!): an algorithm which takes into account the shape of the Edge, the two editing normals on the two extremes vertices and also the position of any opposite edge (for quads) or opposite vertex (for triangles) on adjacent polygons. The Editing Normal will be perfectly balanced between the two opposite positions: this is correct on spherical surfaces equally subdivided (as it is for spherical primitives) . It can be assigned (new!) as the algorithm used when Curved Poly need to update an edge normal.
Curvature Normal: an algorithm which takes into accounts only the shape of the Edge, forcing the Normal to follow the direction towards which the curve of the edge bends. In some situations, it gives a better results, but most of the times it doesn't. For this reason, its not good to assign it as the algorithm to be used any time Curved Poly an update is required. So, this is only available in the Pointings Operator with an edge active.