Hello all,

I am modelling a lot of oblong objects (plane fuselage, ship hulls etc.) either by sweep or loft but mostly by network. It is often hard to model the whole object in one go, as the caps (nose, stern etc.) have sharp turns etc. so that I have to model these separately, which creates continuity problems. Depending on the shape, I have found that it is sometimes possible to use Blend for this if I can give MoI a “tip”, i.e. a flat or other surface to use for curvature.

There are two issues with this though:

1. Often, I would like to provide MoI with only a point as the “tip” of the shape, but that does not seem to work then as MoI ignores the point and does not consider it to be a surface..
2. Sometimes, the fuselage part is made of several sub-parts(and thus as many edges) even though it was generated in one go by the program (this is probably due to curvature I guess). In that case, I do not seem to be able to use Blend versus a shape that does not have similar sub-parts (say a 4-part semi-cylinder and a flat cap). I can extract the edge of the first part and join the parts, but then I have only a curve, not the surface from which to draw continuity.

Am I missing something obvious here?

Jean-Paul

Hi Jean-Paul,

> Am I missing something obvious here?

No - currently the Blend command is pretty limited and will only work for simple situations where you only have 2 pieces to blend between.

Sometimes it is possible to use Edit/Trim on an edge with "Add trim points", to split edges up so that you can have paired pieces but this is not always possible.

In the future I do want to improve Blend so that it can take a range of edges along either side instead of only one edge, but this probably won't get done until version 3.

- Michael

I see. I already learned something about adding trim points. Thanks.

What can be done then to improve continuity between adjacent surfaces?

Hi Jean-Paul,

> What can be done then to improve continuity
> between adjacent surfaces?

Nothing currently - basically to get ensured continuity you have to use either Blends or Fillet, often Fillet can be easier though.

It can be better to build things that come to a sharp distinct crease between the surfaces which then tends to fillet better, filleting can have problems if the surfaces are already partially continuous or nearly so, because it makes for either a tiny fillet strip or one that is collapses down to nothing along a range of the fillet.

- Michael

>
There are two issues with this though:

1. Often, I would like to provide MoI with only a point as the “tip” of the shape, but that does not seem to work then as MoI ignores the point and does not consider it to be a surface..
2. Sometimes, the fuselage part is made of several sub-parts(and thus as many edges) even though it was generated in one go by the program (this is probably due to curvature I guess). In that case, I do not seem to be able to use Blend versus a shape that does not have similar sub-parts (say a 4-part semi-cylinder and a flat cap). I can extract the edge of the first part and join the parts, but then I have only a curve, not the surface from which to draw continuity.

Hi Jean-Paul,

This is just a thought...can you use the *rebuild* script on your build curves so than you can generate a single surface rather than polysurfaces?
It usually works for me when I'm working on a model where I don't care if I don't have totally sharp edges. They still look pretty sharp but have
a nearly imperceptible roundness on the edges and corners due to rebuilding the curves from which they were generated..

Jesse

>This is just a thought...can you use the *rebuild* script on your build curves so than you can generate a single surface rather than polysurfaces?
It usually works for me when I'm working on a model where I don't care if I don't have totally sharp edges. They still look pretty sharp but have
a nearly imperceptible roundness on the edges and corners due to rebuilding the curves from which they were generated..

I've used that trick. It is the sharp corners that seem to split a single network into more than one surface. At times I've used quite a lot of points in my curve to make it look sharp when it really isn't. I've also found it is possible to add a point and then drag it to where I want the sharp bit to be.