Hi Steve,

> I just looked at creating the blend in Rhino4, the results will
> help to show what I mean:-

Yup, that is actually the same problem, if you look at the ends of each of those isoparms, it is a slanted type arrangement.

Basically, you can kind of imagine that blending first creates a set of lines that are connected between the 2 edges.

That line is then converted into a smooth curve segment, and the length of the line determines a kind of "bulge factor" for the shape.

When the line is slanted, it has a bigger length than a non-slanted one, and that bigger length causes too much bulging of the smooth part.

The key to preventing this is getting better matching points between the curves.

- Michael

Hi Steve,

> Doing that actually shows an overlapping edge. I sliced into 4
> quad, then made blend. The top left blend was incorrect (on the scale used)

Doing it on the original size one seemed to help tame it down:



- Michael

From original model:-



closeview



These surfaces will not then join.

Hi Steve, can you please post or e-mail the .3dm for that one so I can take a closer look at it?

It looks like the sweeper/blender is deciding that it is close enough and not refining that area.

- Michael

Hi Micheal,

It is the same model as posted.

But here is the model after I split/blend.


- Steve

EDIT:

Attachment removed/ not now needed.

Hi Steve, yup that is definitely the sweeper thinking that it got close enough and not adding in enough refinement in that area.

This part tends to be a difficult thing to balance because if the sweeper checks for accuracy in too many places it will cause it to take a really long time to complete in more complex cases. But if it doesn't check enough it can let things like this by.

I've added this to my chunk of sweep-related work to see if I can fix it up.

- Michael

Hi Michael,

>> I've added this to my chunk of sweep-related work to see if I can fix it up.

If you are able to correct that, then excellent. I personally would of changed construction to prevent such problems (as I see such problems in many (so called) high end apps).

I dont see this as a failing from MoI, but as I say, if you can control this better, then excellent.


Regards,

- Steve

> If you are able to correct that, then excellent.

I should be able to, I've just got to be a bit careful about not causing too much of an increase in processing time.

- Michael

Thanks guys for all you explanations, it's great learning place here. I get a good result by spliting the edges ... but also get the overlapping problem of course.

>> I personally would of changed construction to prevent such problems.

Well I'm still looking how I can improve the construction in this case :P

Hi PaQ,

You can construct the blend, it only take a few minutes.

If interested:

I projected line onto center of model, then copy/paste the bottom edges:



I then blend the bottom lines (on each side)



Then blend the top projected lines.



I then made sweep using the 3 blends onto the 2 edges.

The blend was correct.


- Steve

Woooow that's genious !!!

Thank you so much manz explain this trick !