G3 filleting problem

 From:  Michael Gibson
461.2 In reply to 461.1 
Hi Kreten - yeah I have noticed that some of the MoI blends are a little "tight" by default - I think that not in this next beta but the one after that I will be able to add a type of "tightness" or "scale factor" control that will let you adjust this a bit for blended fillets, which should let you tweak this.

However, another thing is that G3 fillets are just not really useful for applying to planar surfaces.

The point of G3 (and G2) blending is to try and preserve curvature characteristics of the adjacent surfaces. In the case of a plane, there is no curvature! So if you turn on control points for this G3 blend and look at it from the side, you will see this:

You can see the points are all lined up just only along the tangent, since the plane is flat there is no curvature to match to, so the G3 blend in this case is just a lot more complex and more control points, but does not really provide any geometrical benefit than a G1 blend does.

So this is kind of a problem with assuming that G3 = better in all circumstances. In some circumstances it is not better, just more complex. And being more complex also means there is more stuff that can go wrong...

You can see that the control points are a little bit too tightly hugging towards the edge, leaving a wider space between the inner most pair, that is why the surface looks a little flattened - the scaling parameter that I will add in a bit will let you manipulate this spacing. And I may be able to tweak the default a bit, but the current default works pretty well to avoid bunching when using it on actual curved surfaces.

A G1 blend in that case will produce a nicely evenly spaced blend which won't be tight in the middle like that.

The G3 blends are more useful when applied edges around surfaces that are bending in more directions (that have curvature in them).

Also, can I ask which command you are using in Rhino to generate the G3 blend over there?

- Michael