Thanks, for the answers and I understand that you already have too much to do, maybe with the next releases, however BREP geometries are a hybrid way that supports both NURBS and Mesh geometries, and when I create a BRep file from a mesh file with CAD Assistant I can open it with FreeCAD and recognizes surfaces as if it were a nubrs geometry but nothing can be done besides this.

The image show the mesh file into FreeCAD as an regular geometry with nice smoothed edge without the classic grid such as when import the same as a mesh below


normal import


About B-Rep https://www.opencascade.com/doc/occt-7.4.0/overview/html/occt_user_guides__brep_wp.html

And for info about glTF here https://www.khronos.org/gltf/

Thanks and greetings.

Paolo ;)

Hi Paolo, doesn't FreeCAD support opening STEP (.stp/.step) format files? You should be able to transfer NURBS surfaces between MoI and FreeCAD using STEP format.

Could you clarify what advantage there would be to using .brep format for the transfer instead of STEP format?


re:
> And for info about glTF here https://www.khronos.org/gltf/

It appears to only support polygon mesh geometry? It looks like there are various converters available to convert from OBJ to glTF format, like here's one example:
https://github.com/CesiumGS/obj2gltf


Sorry currently I wouldn't expect to support either of these from MoI directly. The amount of work to the amount of benefit ratio is not good since you can just use other already existing methods for Freecad transfer, and other already existing converters for glTF.

- Michael

Thanks for you time, and the main idea come in mind because the Brep handle both geometry Nurbs and mesh, and the whole idea is was take the boundary info from that to do the conversion taking into account the boundary of surfaces, I know you have other priority before that, and I hope more surprise before final release, no mind anyway, I made several test with Moi3d and it has what I deserve, is a very nice application.

Hi Paolo,

re:
> and the main idea come in mind because the Brep handle both geometry Nurbs and
> mesh, and the whole idea is was take the boundary info from that to do the conversion
> taking into account the boundary of surfaces

Sorry, I'm not understanding this part. Do you mean something like the .Brep file would contain both a mesh version and a NURBS version of the same object?

And that would be something you would create in FreeCAD and then send into MoI for conversion?

But would the mesh be a sub-d control cage mesh or just a rendering mesh made up of triangles only?

If it's a triangle render mesh and there is no sub-d control cage mesh then how would the sub-d converter find a sub-d control cage for the conversion?

And if there is a NURBS version of the object already in the file then why not just transfer the NURBS version over itself, why would there be any polygon to NURBS conversion needed?

- Michael

Mine are more purposeful and hopeful, but I don't know the implicit issues and if it's possible. However the B-Rep file can contain Mesh and Nurbs geometries and not both of the same, however I create the files with CAD Assistant but they are still Mesh.

Thanks very much for answering

Hi Paolo, but what is the goal with using the .brep format file - are you trying to get a better transfer from MoI into FreeCAD?

Are you starting out with a polygon model and you want to convert it into a NURBS model?

- Michael

Yeah the main goal is converting mesh geometry into NURBS, but I found new ways with Moi3D, but the mesh modelling was made having in mind the Moi behaviors on conversion but is also a good way to work with subdivision surfaces, Now I work modeling the base mesh in Blender and the then I rebuild when was is necessary the surfaces into Moi3D, and I get a very clean surfaces. And now Blender open the most file made with Rhino or MoI with an experimental build and manage Nurbs

Below an hull created in Blender then converted to NURBS with Moi and imported as NURBS inside Blender, with that workflow I can have awesome nurbs inside Blender no more mesh..

Hello pafurijaz -
This Blender (polygons) to Moi (nurbs from subdivisions) and back to Blender (imported nurbs) path is very interesting.
What is the exact link or release number of the Blender build you used ? And, would you mind sharing an example .blend of a part ?

Hi, here are some links, for the files I have to search and prepare, That is the workflow is simple,I import the 3dm files (does not support trimmed surfaces for now) with the soc2014 version but viewing is a bit problematic, then save the file and open with a standard version of Blender, then edit the various surfaces because they are poorly displayed, I do nothing special but select the end point 'U' and 'V' several times. then the file is displayed correctly and is a NURBS surface.

NURBS soc-2014-nurbs branch update to Blender2.8(windows)
https://blender.community/c/graphicall/vkbbbc/

https://blenderartists.org/t/branch-soc-2014-nurbs-update-to-master

here an old post about this news
http://moi3d.com/forum/index.php?webtag=MOI&msg=9686.3

Hey, thanks ! Will give it a spin asap.
[edit] Alright, tried it out, I see - it's pretty interesting indeed, just not quite ready yet but I can see the potential eventually. Will definitely keep an eye on it.

Hello everyone,

I know this has been discussed before (a lot actually), but I'd like to again suggest some sort of "polygon mesh reference" display similar to image references. No user interaction with the geometry whatsover except for transforms (position, rotation, scale for the object as a whole) and displaying it alongside with the NURBS model in the viewport to serve as a 3D high-poly reference to model off of.
I realize that this is a feature which would need crazy amounts of developing time to implement, but it would make MoI the go-to solution for hobbyists who e.g. want to take a scanned object and re-model it accurately.

Hi Stwend,

re:
> it would make MoI the go-to solution for hobbyists who e.g. want to take a
> scanned object and re-model it accurately.

There have been a lot of requests for this so it's kind of on my radar but one of the things that helps keep MoI to be streamlined and easy to use is not trying to focus on doing too many different kinds of specialized tasks all jammed together into one single interface.

Right now this type of reverse engineering task is one of those general "not focused on" areas. Really to do a proper job of making it work would involve more than just displaying it, there would need to be a variety of tools added in addition to that to make the whole area work decently.

If you need to do this kind of work a lot, some other program like Rhino would be a better tool for that job right now.

- Michael

Hi Michael,

I appreciate you answer a lot. It's good to hear the feature is on your radar, which is all I hoped for - right now I'm using Blender for turning the scan into a decent model, and I'm so far in that it wouldn't make sense to migrate to Rhino now, but let me tell you it's a huge pain to create the object (a car) using subdivision modeling. When I need to do that kind of thing again in the (far) future I hope I'll be able to use MoI for the job.

Best,
Stefan

Hi Stefan, cars are kind of a difficult model to work with anywhere. They are also difficult to do in NURBS because they have a lot of swoopy curved surfaces that usually need to be modeled in NURBS as extended patches that are then trimmed. That's in general a more finicky and advanced type of surface modeling.

The key area where NURBS modeling is way way easier than sub-d modeling is when your shapes can be well defined by 2D profile curves and boolean operations. That is not usually a fit with a car though.

It's a type of model that I think can be easier to do in sub-d because you don't have to worry so much about extended surface shapes.

- Michael

An easy workaround for that I use in Rhino I import the OBJ model than I extract all curves and leave the surfaces behind if the OBJ is not to dense leaves me a cage that I can then trace over I have used this on projects many times. I import that cage into MOI and get clean precise rebuilds.

There is also a standalone helper program you can get at http://moi3d.com/resources#Obj23dmWireframe_converter that can open an .obj file and generate a wireframe .3dm file from it that can then be loaded into MoI. It makes line segments from all the polygon edges.

- Michael

Hi Michael,

In this link, (hard to believe that it was two years ago), you mentioned "...new evaluateCurvature(t) function. But it might need an additional method for getting curve parameter values for points equally spaced along the curve, I will see about adding that in."
also "...I'm planning on adding another batch of curve functions for the next beta as well, that should do the trick..."

https://moi3d.com/forum/index.php?webtag=MOI&msg=8814.12

I reviewed the newer MoIV4 beta posts, and did not find new curve functions.
Will you be posting such new methods?

The reason that I ask is that the new script that I am working on uses curve r(t) values at "t" to form a sphere of radius r(t) at parameter point "t2" of a path curve.
It seems to me that the parameter "t or t2" values of the two curves may be of different SPACING or NON-UNIFORMITY. (In some cases.)
(In a sense I'm using t and t2 as uniform time parameters...? (unit speed curve??)) (The script will be a "sphereSweep" script.)

(I am compensating for min and max values of t and t2 being different. Say (0 <= t <= 1) for radius curve and (0 <= t2 <=5) for path curve.)

Also it seems that given a t3 parameter value of a curve, and existing script methods, a point currently can be found, but given a point on the curve, its t3 value cannot currently be found by script.

- Brian

Hi Brian,

> In this link, (hard to believe that it was two years ago), you mentioned "...new evaluateCurvature(t)
> function. But it might need an additional method for getting curve parameter values for points
> equally spaced along the curve, I will see about adding that in."
> also "...I'm planning on adding another batch of curve functions for the next beta as well, that
> should do the trick..."

The function for getting curve parameters for equally space distances along the curves hasn't made
it in yet but it should be possible to accomplish using the ArrayCurve command to generate equally
spaced points and then crv.dropPoint( pt ) to get the parameter value for each point.


re:
> Also it seems that given a t3 parameter value of a curve, and existing script methods, a point currently
> can be found, but given a point on the curve, its t3 value cannot currently be found by script.

It can be - that's the dropPoint() methods added in the Jan-22-2020 v4 beta, there is a collection
of all the V4 beta release notes gathered in one spot here: http://moi3d.com/wiki/V4Beta

Add script methods for dropping points:
curve.dropPoint( pt ) - returns curve parameter value of closest point on the curve to the given 3D point.
curvesegment.dropPoint( pt ) - returns curve parameter value of closest point on the curve segment to the given 3D point.
face.dropPoint( pt ); - returns 2D uv coordinate point of closest point on the face to the given 3D point.
brep.dropPoint( pt ); - finds closest point on brep to given 3D point. Returns a list with 3 items, 0: Face object that the closest point is on, 1: 2D uv coordinate for the face, 2: 3D coordinate of the closest point.

The dropPoint() method takes a point as the input, it can be either on or off the curve. It then returns
the parameter value for the closest location of the curve to the point. If it is on the curve then you can think
of it as a conversion from 3D point into curve parameter value. If it's off the curve then it's like you were to
draw the shortest line from the point onto a spot on the curve and it will give the parameter value of that
curve location.

- Michael

Thank you very much Michael.

Your "closest point" explanation is also very helpful.

dropPoint() method is perfect for my script. With array points, code from good old LineWeb script.

[So, I did not read the most recent release notes,but have now :-) ]

- Brian

You're welcome Brian. That's new so please let me know if you have any problems with it.

- Michael