Hi
If I change the highlighted points in object A away form right-angled like in object b so I get a bump on the red part of the object. What has to be changed that it looks correctly.
Thanks for any ints.
nos

Hi nos - instead of using Sweep for this case, I'd probably try to do an extrusion that has some initial sharp edges and then use Fillet to round them off, something like this (also see attached 3DM file):



With that method you can be pretty free to adjust the bottom profile to different forms.


The problem with using sweep in this way is that sweep functions by basically dragging a profile along the 2 guide rails - in a certain sense it is a sort of tubular construction mechanism since it generates a shape by a series of cross sections. When you have the ends collapsing down especially at a 90 degree angle to each other it kind of becomes an unnatural situation for a tube - it kind of creates a sort of tension in the shape.


Another way to kind of describe the problem that you were seeing with sweep is imagine trying to sweep between these 2 shapes like this:



Because the sweep action works by dragging the profile while marching along each of those curves, trying to sweep with something like this as the rails will generate profiles that connect to each other like this:



So you can see that there's kind of a mess where some profiles sort of backtrack over top of the previous ones just one side, and each kind of messy area corresponds to a place in the wiggly curve where it changed direction to come in at a 90 degree angle towards the other rail.

So that kind of 90 degree angle turn towards the other rail is something that is kind of problematic just with the general mechanism of Sweep, especially when you actually exceed 90 degrees...

- Michael

hi michael, the object I uploaded was more a test for my to figure out when sweep works and when not. The object I try to make is more complex, see this Image. Until now I did manly stuff for mechanical processing which is simple to construct in moi. This is more of a organic form wich will be 3d-printed and I have all the freedom to shape the object :-). However I'cant figure out what tools I have to use to make this form. The form is a quarter part and will be mirrored along y and x, so I guss I have to make shure the quarter Part maintains tangents.

Can you explain how I have to construct object like this, respectivly what's the criteria to use the specific tools and are there any turorials about using moid for "organic/freeform shapes"?

Thanks for any hints
nos

Hi nos - MoI is not really the best tool for the job for making totally organic all melty-looking forms. A polygon modeling program using sub-d smoothing tends to be a better fit for those kinds of shapes.

Basically, MoI is more oriented towards drawing profile curves to generate your shape.

When a form is all melty all over, that can make it hard to create profile curves for it, because for a profile curve to work well it needs to strongly define the shape created from it - and something very blobby and of not distinct form is not so strongly defined by a single profile curve.

But if you can analyze your shape to determine some underlying major pieces that have transitions between them, that can help to guide you in how to construct it in MoI.

So for example in your shape here, notice how you've got some tight bends in these areas here:



When you have a tight bend like that, that implies that there is some kind of transition happening there, and if you've got a transition between different forms, you want to build those forms separately and then let the transitions be created by filleting rather than trying to directly draw those transition areas like you're attempting to do.

So for example you'd probably try to build some forms that follow the broader parts of the shape, kind of imagining them without those tight bends in them first, so build some sheets of these sections:




Right now you're trying too hard to generate a multi-formed shape that has more than one underlying form to it all in one single surface. That will tend to have a lot of issues and be difficult to control well. You've got to try to get each surface (like each sweep that you do) to try and follow just one somewhat more simple form, let them collide into each other sharply to start with and then make a rounded transition with fillets.


> respectivly what's the criteria to use the specific tools and
> are there any turorials about using moid for "organic/freeform
> shapes"?

There's not a lot of tutorials on this because it's a kind of difficult area, and getting a lot more strongly into the area where polygon modeling with sub-d smoothing just becomes a better overall tool...

But if you want to do it with MoI, the key thing will be a sort of shape analysis to determine if there are some broad underlying forms that you can focus on building first, and then add transitions by blends or fillets rather than trying to do too much all in one single surface creation command.

- Michael

Hi Nos, so basically something along these lines here:



Each piece can have some contouring to it, but it's trying not to do too much in any one individual surface.

See this recent thread for some tips on making some slightly cupped surfaces using sweep:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4296.5


When you've got a set of surfaces that are all overlapping each other like this, you can use the Construct > Boolean > Merge command to form them into a volume with one command trimming away the outer part - it's also possible to use the Trim command as well but that will involve picking the pieces you want to discard more manually.

So that builds a block with sharp edges like this:



Then you rely on filleting to do the more tightly bent transition areas:






You kind of have to give up some immediate control, you're going to focus on drawing some broader shapes of the piece instead of trying to actually directly draw profiles that contain the transition areas in them already.

Also the "Shape" option for fillet can be useful for this kind of a thing - try setting Shape: G2 Blend to build a kind of more natural looking connection surface instead of the regular fillet surface that has an exact circular arc shape to it. You can also then adjust the "Bulge" slider to tweak the transition areas in addition to setting a radius value.

- Michael