Full Version: How to reduce points of a surface

Good day.
I am trying some surface modeling here.
The curves were done in Moi exported as 3dm to plasticity to be done with xnurbs then exported as step file back into Moi.
Now in Moi how would I reduce the amount of points so I can further modify the surface?

Also would these the best exporting files to be doing this?

Tnx.

Image Attachments:
moixtest.JPG 

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Hi Matadem,

re:
> Now in Moi how would I reduce the amount of points so I can further modify the surface?

Try Mo's RebuildSurface script here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=11191.1

- Michael

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cant seem to make it to work.

attached the file if anyone want to try it.

Tnx!

Attachments:
moi patch.stp

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Hi Matadem, what are you trying to accomplish by reducing the surface's number of control points?

It's a trimmed surface and rebuilding it will mutate the shape of it and the trim boundary on it won't be able to join up to the same places.

- Michael

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Rebuild Surfaces only rebuilds 3 or 4-sided surfaces (for now!).

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Good day.

I just want to test to modify the surface after its been created...I am practicing for something I want to make.
I created the model in Nvil.

and now I am trying to do the same in Moi/plasticity.
Wireframe in Moi, surfacing in Plasticity, back to Moi for final details.


Tnx!

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Hi Matadem, it's generally better to do surface control point modification in a polygon subd modeling program and not in NURBS.

The main reason why is that in a polygon modeler you can add in a single individual new vertex anywhere you want and hook up polygons to it.

The way NURBS surfaces are set up they are defined by a grid of points in rows and columns. So you can only add in a new full row or column into the control point grid, you can't add just a single point.

NURBS surfaces are strong in different areas than that, especially with Booleans because NURBS has the concept of a "trimmed surface" where there is an underlying surface that has a trim boundary. So when you do a boolean on a NURBS model the underlying surfaces remain the same and just the trim boundaries are changed. Polygon modeling doesn't have that concept, when you do booleans in a polygon modeling program the geometry gets diced up into more and more little fragments.

But if you want to experiment and get a lower density surface without regard to how accurately it keeps the shape of the original, you could use this process:

(which again I don't recommend doing, you are better off doing modeling by surface control point manipulation in a poly modeling app)

Select one edge of your surface:



Use Ctrl+A to select all edges:



Use Delete to erase the trim boundaries and recover the full underlying surface:



Select the surface and run Construct > Curve > Iso and make some isocurves in the U direction:



Add more isocurves in the V direction of the surface:



Select the outer 4 boundary curves of the surface and use Ctrl+C/Ctrl+V to duplicate them as standalone curves.



You now have a grid of curves, you can delete or hide the original surface and select your new grid and run Construct > Network to build a surface from it.



Set the options for the Network command to have "Mode:uniform" and "Point count:1".

You will now have a surface that approximates the shape of the original but will have a density only driven by how many U and V isocurves you extract and not connected to the original surface's control points:



But don't do this - a CAD program is not the right tool for this type of work. If you want to model by sculpting a 3D point cage do it in a Poly modeling app where everything is tuned for doing that.

- Michael

Image Attachments:
MatademSrfRebuild1.png  MatademSrfRebuild2.png  MatademSrfRebuild3.png  MatademSrfRebuild4.png  MatademSrfRebuild5.png  MatademSrfRebuild6.png  MatademSrfRebuild7.png  MatademSrfRebuild8.png 

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Hi Michael,

After a decade or so of using MoI I continue to be amazed at what it is capable of. Aside from all the time and effort you have put in to make it so, your explanations in the documentation and forum (like this one) are like a masters class in what's going on and why. You are amazing and I am grateful. MoI is a wonderful tool!

--Larry

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Thanks Micheal.

I do understand that while polygons are better in some cases especially to make later changes...but in the end I need to have exact measurements since they will need to be machined at some point.
Please add some xnurbs to Moi :D

and yes after all these years Moi still impress me with its capabilities

Thank you!

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Thanks Larry and Matadem!

- Michael

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