Is this a bug in .iges file from MoI or not??

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 From:  boatstalker
658.1 
In need to convert my work created in MoI to .dxf 3D mesh

Using Prosurf for this purpose results in shapes originally trimmed or cut away in MoI to reenter the scene. Here is an example: Picture1 shows the funnel created in MoI and saved as .iges. Picture2 shows the .iges as it look when imported to Prosurf. Picture3 shows the funnel after it has been saved as .dxf 3d mesh in Prosurf and the resulting file opened up. The top of the original coneshape created in MoI and cut away has had an unwelcome comback. Is this a bug in MoI or in Prosurf? P.s. Attaced are the appropriate files resulting from the procedure described above.







Thanks in advance,

Boatstalker

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 From:  Michael Gibson
658.2 In reply to 658.1 
Hi Boatstalker, it seems to be a bug in Prosurf. Can you please send the .iges file to their technical support for them to confirm?

I can't seem to find anything wrong with the IGES file itself - it loads into both MoI and Rhino fine and Rhino is able to make a proper DXF from it.

It appears that Prosurf is ignoring the trimming information.

When you do any cutting operation on a surface (for example booleans), what happens is the same surface actually remains "underneath" and there are new "trimming curves" that are calculated. Trimming curves are curves that live on the surface and mark regions of the surface that are supposed to be inactive. There is some other explanation of this here: http://moi3d.com/forum/index.php?webtag=MOI&msg=170.25

It appears that ProSurf is ignoring the trimming information and only using the underlying surface when generating DXF polygon data. I'm not sure if it ignores all trims or if there is some reason that it is ignoring them for just this particular case. To test you could draw a plane and cut a circular hole in the middle of it - if ProSurf ignores the circular hole when making a DXF, then it would seem that they don't support trims in the polygon generation.


Another way to get your DXF would be to export to either OBJ (probably use quads & triangles option), 3DS or STL formats out of MoI and then use a polygon format converter, such as 3DWin (http://www.tb-software.com/products_2.html) to convert it into DXF format.

- Michael
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 From:  boatstalker
658.3 In reply to 658.2 
Michael,

Thank you for explaining this issue. I have now imported several other cuts into Prosurf and this happens sometimes and sometimes not. If the residual trimming lines are joined or unioned before saving and exporting to Prosurf this doesn´t happen.

However for some reason the commands "join" or "union" do not always seem to work. For example the deck bridge on the catmaran below was constructed by a sequnece extruding, intersecting, deleting, mirroring and moving surfaces. There is a "scar" from this procedure left on the left side of the deck bridge. The scar on the right was easily removed using the "union" command, but not on the left side.

Is this some kind of a bug in the NURBS kernel library or me just being clumsy?

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 From:  Michael Gibson
658.4 In reply to 658.3 
Hi boatstalker - can you please post your model file? I can't really tell what is wrong just looking at a screenshot.

For 2 pieces to join, they have to be connected at a pretty tight tolerance - if there is too much space or a gap between 2 pieces they won't join. That might be what you are running into, but if you post your model file I can examine it more closely to check.

Is the scar you are talking about the line running down the deck? That looks like a surface edge. Most of the time if you join or union edges like that will remain in the final result, mostly the only exception is on some handling of planar surfaces where sometimes a union can combine 2 planar surfaces into one larger plane and remove interior edges.

- Michael
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 From:  boatstalker
658.5 In reply to 658.4 
Michael,

This is probably just a surface edge. Don´t worry. I justed needed an excuse to post a picture of my catamaran :-)

The "trimming bug" previously mensioned in this thread is definitely some kind of a "kink" Prosurf, not MoI.
Here are some pictures of what the .dxf mesh generated by Prosurf looks like and as a comparison we have the .dxf mesh
generated by Rhino.




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 From:  Michael Gibson
658.6 In reply to 658.5 
It looks like your catamaran is coming along nicely!

Probably somewhere along the line you mirrored one surface and joined, creating 2 surfaces with an edge between them, then possibly that assembly got trimmed with the center line not arranged right in the center between the trimming objects.

It looks like that in-between piece is a straight connection (sometimes called a "ruled" surface).

So to tune this up what you can do is select both of those surfaces in between your hulls and delete them. Then select the 2 inside edges at the top of the hulls, and then do a Construct / Loft between them.

That will build a new single surface connecting those pieces - that will not have any interior edge anymore. Then you can join those hulls and the connecting surface together into one object.

Let me know if you need more detailed info on these steps - if you post your model or e-mail it to me, I can show you some step-by-steps images on your model if you want.

- Michael
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 From:  boatstalker
658.7 In reply to 658.6 
Michael,

Thats a brilliant suggestion. No need to guide me further through the steps. It couldn´t be more simple. Thanks a lot. In return will invite you to go fishing with me when the boat is finished :-)

Best regards,

Boatstalker
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 From:  Michael Gibson
658.8 In reply to 658.6 
Here is the scar removal procedure:


First, delete the central piece that has the unwanted middle edge in it, and then select these 2 edges:




Then use Construct / Loft to get this scar-free result:



A couple other notes - MoI doesn't seem to be doing too good of a job of making the display mesh for some of these pieces, some things look more jagged than they really are. That's something that I want to tune up more in the future but it might not get better until after V1.

EDIT: oops, didn't see your last post in time, well here you go anyway! :)

- Michael
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