Hi Pilou,

> Numbers of control points are they modified?

Yes, definitely - otherwise things like a plane that only has 4 corner control points would not be able to be deformed.

That's one of the problems with these kinds of deformations though, that it can tend to increase the complexity of the surfaces quite a bit by having a lot more control points in the deformed result.

- Michael

hi michael
I did try this with rhino but it seams I miss something, cause the result is shrinked. Do you have any idea why that is?
~nos

If I use the "Plane" Option it works, also paste back, very nice.








But no luck with the pre-defind surfaces.



I attached 3dm file.

~nos

if I use the Plane-Option in rhino but give it the same shape as the base surface the object get stretched along the target surface and dosn't keep its original size.

Hi nos - so that shrinking effect is happening because that one plane surface is a trimmed surface. The underlying surface is actually a fair bit larger than just the trim curves, and the way that Rhino's FlowAlongSrf command works, it just uses the underlying surface directly and doesn't pay any attention to how it is trimmed.

To see the underlying surface, in MoI select that surface and then turn on control points and zoom out a bit and you will see the 4 corner control points for it.

Because the base surface is actually fairly large, that then makes the result in your target surface to be small since the object being morphed is actually small in comparison to the base underlying surface.

There is some description of what an "underlying surface" and trim curves are here:
http://moi3d.com/wiki/FAQ#Q:_Why_does_show_points_work_for_some_objects_but_not_others.3F

So to fix it, select that surface and run ShrinkTrimmedSrf on it, either in MoI or in Rhino. In MoI you need to press the Tab key and type in the command name, or set up a keyboard shortcut for it, it is one of the commands that does not have a button for it in the UI yet.

Running ShrinkTrimmedSrf will shrink the underlying surface down to the trim curves so that it will be the same size as the trim curves and should behave more like you were expecting.

- Michael

HI again
I played around with Rhino and as far I understand, the size of the aligned object terminated from the relation of the size from base- and target surface.

I also found out that I can move the base surface to change the position of the aligned object and change the vu direction to change the rotation. But if the target surface is a complex object it seams not possible to find the same size for the base surface. So I have no clue how I have to keep the size from the base object.

Also finding the exact position. The position should be the same as the base object, except that it should be aligned to the target shape. Do I miss something. What I would except is that I could set some sort of anchor points on the base object and the target surface witch would be on the same position and determinate the location. Hope that makes sense.

Has anyone an idea how to achive this?

Thanks for any help.
~ nos

Ah, I did also a post in the meantime. I did try the shrink command. But now it's to big. So could you please explane what determinates the size and the position of the aligned object (beside the trimming).

Thanks for pointing this out
~nos

Hi nos,

> So could you please explane what determinates the size
> and the position of the aligned object (beside the trimming).

It just maps from the base surface to the target surface, but as I mentioned above it uses the underlying surfaces for this mapping, so look at the full untrimmed surface (one way to see it is by turning on control points) to see what will actually be used for the mapping.


> But now it's to big.

So that means that you want to increase the size of the base surface plane - scale it up or something so that the object you are deforming is contained inside of it with some space around it rather than having them right snug up against each other.

The same relationship of the object being morphed in relation to the base surface will then be applied to the target surface. That includes spacing, so increase the spacing around the base surface to then apply that same spacing to the target surface.

- Michael

> It just maps from the base surface to the target surface

ok, but what's the size of the target surface? Cause when the size of the aligned object is the result of base-surface/target-surface and I have to keep the size of base-object and the aligned-object the same, I have to figure out the size of the target-surface.

~nos

Hi nos, the size of the target surface is... well, it's size.

Every NURBS surface has a 4-sided layout to it the same as your plane there, with a closed surface it's just like you have a sheet of paper that is rolled up so that 2 of its edges are touching one another.

If you can imagine that sheet of paper being rolled up into the shape of your closed target surface there, the size is the size of that sheet.

So also the "seam edge" of the surface (where 2 of the edges of the rolled up surface touch each other) is significant - that will map to 2 of the edges of the flat plane. You may want to use the SrfSeam command in Rhino to move the seam to some other spot if you want your placed surface to start in some other spot than the current seam.


re: keep the size the same - that's generally not possible to do with these kinds of morphing transformations. A surface is not restricted to only have one fixed size in a direction, it can easily have things pinched together in some areas and be wider in other areas, and with your bendy surface it looks like you have that kind of a thing since it isn't just one single rigid shape in one direction of it.

If you wanted to preserve the size, that would require some kind of evenly shaped target and not one that was stretching and deformed in different areas of it.

- Michael

Hi nos, also in some cases you might want to use the Flow command in Rhino instead of FlowAlongSrf.

The Flow command uses curve objects to define the transformation, from a base curve to a target curve. That may be a bit easier to visualize the result, I believe the distance as traveled along the base curve will map to distance traveled along the target curve in that case.

FlowAlongSrf on the other hand does not map distance to distance in a direct 3D distance sense - instead it will map between the UV space of the base surface to the UV space of the target surface. So this means that things like compression of the UV parameter space in the target surface (things like surface control points unevenly distributed) will result in uneven distribution of the morphing as well.

With the curve-based Flow command being distance based it may be easier to get a distance preserving result.

- Michael