I have a mesh created from photogrammetry in 3DM format - loads into MoI fine.

What I want to do is create multiple objects on top of the mesh and export individually. I.e. using the mesh as a surface or skeleton or framework to design objects around, so that when the objects are 3D printed they will fit onto the real surface.

What is the best way to accomplish this?

Normally I would create an assembly in my MCAD package but it really struggles with organic shapes like surfaces and won't even load this one.

Thanks, Andy

Without any example seems it's difficult to say something! :)

SIze Object / Surface, you say organic but like what ?
etc...

Hi Andy, there are a couple of different methods you could try to see what you like best.

One way is to use the View >CPlane tool to set the construction plane to a spot on the surface where you want to construct. That will relocate the drawing plane and all the ortho (top/front/right) views to be centered and oriented around that area so when you draw you'll be drawing in that local coordinate system:
https://moi3d.com/4.0/docs/moi_command_reference5.htm#cplane

The other way you can do it is to create a part aligned with the regular world coordinate system and then use the Transform > Orient command to move and rotate it into place on the surface:
https://moi3d.com/4.0/docs/moi_command_reference8.htm#orient

- Michael

Thanks Michael.

Is there a way to make the display of the mesh a bit easier to work with? There are lots of triangles so it looks like a big, thick mess of black lines. Perhaps thin and light grey?

Andy

View right
Separate the "red object"
Boolean with the box (Will works also with a simple rectangular face )

But your original object is some special very intricated itself! :)

Another one - I think my surface is too complex for MoI to work with easily. I can't extrude it. I've tried two ways to get it into MoI - use the obj to 3DM converter and the obj import in V4.

Here is the file:

https://www.dropbox.com/s/53srfylmixf1zay/SurfTest.3dm?dl=1

Is there a way to simplify it to an approximation so there are less facets?

Thanks, Andy

Thanks. I deleted my post because I thought the surface wasn't really a surface, just a collection of lines with no faces, so my mistake. I was trying to see if I could get an indentation into the block using the surface.

Andy

error 400 for file ! use the loading system of the forum...or check your send... ;)that'

ELse you can erase the box

Planar the "rectangle surface"

make the Trim

that works even with your first file

Pilou, you are too quick! :) Try now. Andy

Hi Andy,

re:
> Is there a way to make the display of the mesh a bit easier to work with? There are lots of triangles so it looks like
> a big, thick mess of black lines. Perhaps thin and light grey?

MoI is not designed to work with triangle mesh geometry so it might be difficult to use it in this way.

But you might try using Edit > Lock to lock the mesh so it's not selectable and then it will be grey.

If you want thinner lines, try going to Options > General > "Edit .ini file" button and in the moi.ini file set:
UseThinAntiAliasing=y

- Michael

For a simplication with less faces, you coukd use :
- Meshlab
- instant meshes

Hi Andy,

re:
> Another one - I think my surface is too complex for MoI to work with easily. I can't
> extrude it. I've tried two ways to get it into MoI - use the obj to 3DM converter and
> the obj import in V4.

The problem is you don't have a CAD surface, it looks like you have polygon mesh data in the form of triangles.

The OBJ import in MoI V4 is for converting a sub-d control cage into a CAD surface, your mesh looks like it is not configured as a sub-d control cage where it should be a sparse control cage made up of quad polygons.

MoI and other CAD programs in general are not designed to work on this kind of dense triangulated data.

You will probably need to use a polygon mesh editing program to work on this type of data, not a CAD program. I'd recommend trying 3D Coat or ZBrush to start with.

To work with it in CAD you would probably need to go through a process called "reverse engineering" that fits spline surfaces to dense triangle mesh scan data. it's a complex process with pretty expensive tools like Geomagic Wrap for example. It's also possible to approach it with a polygon modeling toolset where it's called "retopology". There are retopo tools in many polygon mesh editing programs again like 3D Coat.

MoI is just not the right tool to work directly on the kind of data you have there.

- Michael

Thanks Michael - I understand that. What I want to do is use the surface as a scaffolding to work on top of to create NURBS shapes. I don't want to change the surface unless I have to because it's the reference.

Is that doable?

Andy

Something you can try

Draw a SOlid plane where you want the Trim

Make a Boolean "Merge"

Then Press Tab and write ExplodeMove

your 2 parts will be well separated

As your file is a lot of very pieces...maybe that take a no reasonable time!

OK, I have now tried this:

1. object obj in meshlab
2. Go to Filters -> Remeshing, Simplification and Reconstruction -> Simplification: Quadric Edge Collapse Decimation
3. Enter target of 1000 faces
4. Export
5. Use Michael's obj23dm converter, choose closed polygon for each face
6. Load into MoI

OK, looks good. A lot less clutter. But the "surface" is just a collection of triangles (closed curves) and there are no faces.

So what I want to do now (for example) is create a NURBS surface over the top, maybe just part of it, and then extrude that. But how?

Thanks, Andy

HI Andy,

> Is that doable?

Not really, at least not very easily. I guess it's technically possible but it's not an area of work that MoI is currently focused on so it's not going to be particularly easy.

If you don't want to change the data then to start with you would not want to use the sub-d importer because that applies a sub-d smoothing process onto the polygon control cage which does modify shapes making a kind of melty smoothed down result. This works fine when the polygon mesh has been set up from the beginning to be used for sub-d smoothing but otherwise not.

- Michael

Hi Andy,

re:
> So what I want to do now (for example) is create a NURBS surface over the top, maybe
> just part of it, and then extrude that. But how?

That's a process called "reverse engineering" and it's a pretty specialized and advanced type of use for CAD.

MoI is not designed to be a reverse engineering tool so it's not really a good fit to try doing this in MoI.

You might try Rhino, there are some reverse engineering tools made for it some info here:
https://wiki.mcneel.com/rhino/reverseengineering

- Michael

Seems it's only triangles



try to make quadrangles before the importation! ;)

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