Full Version: Using a Surface as a Framework

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Seems it's only triangles



try to make quadrangles before the importation! ;)

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When you created your obj to 3DM converter what was the intended usage?

I tried creating a surface in Meshlab from the simplified point cloud (surface reconstruction), saved as a new obj, run through your converter, but still no faces. So I guess your converter does not generate faces?

Andy

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I think if I could generate curves from silhouettes of the surface using the CPlane option, then I think that would get me most of the way there. Seems the silhouette feature won't work on my collection of triangles, because it's not an object?

Andy

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Hi Andy,

re:
> When you created your obj to 3DM converter what was the intended usage?

Primarily for cases with structured objects, like boxes and cylinders, stuff like that which is easier to reverse engineering than freeform surfaces.

It's not an area that MoI is primarily focused on, which is why it's a separate tool and not a built in function.


re:
> So I guess your converter does not generate faces?

Correct, the converter generates closed polyline curves, not faces. But you can turn triangles into faces using the Construct > Planar tool in MoI.

However, like I've been describing previously MoI and CAD programs in general are not designed to work on faceted triangle data.

- Michael

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Hi,

If you want to create a nurbs surface with your map, I tested a method months ago.

Use Meshlab
- align your ground to be with a top view
- render with shader depthmap to create a heightmap
- scale the rendered image as you want for the precision (warning every pixel will give you a profile curve later)
- use the heightmap plugin in MOI. I think it's a Max plugin
- You will have a X or Y profiles (use only one if possible)
- Now you have curves to do a lofting (perhaps use loose option to smooth).

This lofting is a nurbs surface and you can use it
and delete curves.

A boolean operation can give you a clean surface which could be extrude or could be merged to have a real solid.

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Hi Andy,

re:
> Seems the silhouette feature won't work on my collection of triangles, because it's not an object?

The silhouette command in MoI works on surfaces or solids, not on curves.

It's not designed to work with faceted data, it's main job is for building silhouette curves on curved surfaces.

- Michael

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"Primarily for cases with structured objects, like boxes and cylinders, stuff like that which is easier to reverse engineering than freeform surfaces."

What are the steps to reverse engineer a structured object?

Andy

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Thanks Phiro - sounds interesting, I will give it a try. Andy

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Here the height by Max Smirnov ;)

http://moi3d.com/forum/index.php?webtag=MOI&msg=7547.52

place file(s) inside the moi commands folder
relaunch Moi

Press Tab and write _heightmap

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A problem you could have with your beginning object is the overhangs in the ground and the holes.
The overhangs gives only the higher point and hide lower points in depthmap. Holes give a 0 level, not an hole.


But the result could be like this 2 surfaces.


Yes Michael, you're right...
it's not an orthodox CAD software usage...

Image Attachments:
2021-04-24_01h37_26.png 

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Hi Andy,

re:
> What are the steps to reverse engineer a structured object?

Draw lines for planar spots, use Circle or Arc through 3 points snapping on to triangle corners, use the lines and arcs to extrude surfaces.

- Michael

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You can have easily some curves of your object

here the horizontal arounding after an extrude :)
make the same on some vertical sections planes on this same object
At the end make network...

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Hi Andy,

re:
> What are the steps to reverse engineer a structured object?

There's an example here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=9208.1

- Michael

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How about this?

1. Create object of precise shape and size
2. Slice object using surface to create the back of the object
3. Offset surface X mm
4. Slice object again with surface to create the front of the object

I.e. splitting the object into three parts and keeping only the middle.

Is that possible?

Andy

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Of course yes but it's completly different that you want to make with your "triangulated" object! ;)

If you create directly with "Nurbs" curves, Surfaces etc ... you will not have problem!

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Hi Andy,

re:
> Is that possible?

No probably not easily if the "surface" is a bunch of triangles instead of an actual smooth surface. It will be difficult to offset something like that.

- Michael

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Hi Andy,
So your surface looks like Crumpled paper!!!

I opened it in 3dcoat without modifying it. Then I ran a command called "Instant Mesh" with the auto setting. I set 3200 as the poly count. If you really wanted or needed quality results, you would retopo it properly i guess.

The result below.

The retopoed mesh along side the same file imported using MoI's SubD tool:



And the Imported Mesh, alongside running Max's SubDiv9 on it.



In both cases, the imported mesh is there by means of Max's ImportObj Command.

I wouldn't try to work with the original 3dm file....

Image Attachments:
quick_redo.jpg  quick_redo_subdiv9.jpg 

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Thanks BurrMan and to everyone who replied.

Here is what I just tried.

1. Open obj in meshlab
2. Go to Filters -> Remeshing, Simplification and Reconstruction -> Simplification: Quadric Edge Collapse Decimation
3. Enter target of 1000 faces
4. Export obj
5. Use Michael's obj23dm converter, choose closed polygon for each face
6. Load 3DM into MoI
7. Select everything
8. Choose Construct -> Planar
9. Save as 3DM
10. Open desired part in Alibre Design
11. Import 3DM surface
12. Trim model using surface
13. Move surface
14. Trim model using surface (reversed)
15. Export as STEP
16. Load STEP into MoI
17. Delete surface

Alibre Design is ACIS based and doesn't like triangle-based geometry but it seems to cope OK with slicing an ACIS object with a triangular surface.

That's a lot of messing around, would be nice if MoI had this trimming function as well.

Andy

Image Attachments:
ADSurfSlice.png  ADSurfSlice.png 

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If you can drop it down to 1000 faces for the retopo, you can bring the surface into MoI and Shell it there too.... Did some booleans, etc. too.....

Image Attachments:
shelled from 1000.jpg 

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Clean....

Image Attachments:
hidden edges.jpg 

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