Here is a link to a recent paper, with an algorithm, for fitting arc splines to NURBS:

https://www.researchgate.net/profile/Xunnian_Yang/publication/3845146_Approximating_NURBS_curves_by_arc_splines/links/594ca7eb458515e70348b782/Approximating-NURBS-curves-by-arc-splines.pdf

- Brian

Thanks Brian!

- Michael

You are welcome Michael.

I'm still reading the paper...
From my limited understanding, the purpose of such a dxf export in arc/line format would be useful?
Maybe tangents of NURBS curve would be exposed to scripting in the future?

- B

A closer look shows that the paper was uploaded in 2017, but was written in 2000.
There are 2 other similar papers by the author in ~2001, and the paper is cited by other papers.

Piegl & Tiller: https://documents.tips/documents/biarc-approximation-of-nurbs-curves.html

- B

Hi Brian,

> I'm still reading the paper...

Yeah often time research papers can take a lot of effort just to read and understand.


> From my limited understanding, the purpose of such a dxf export in arc/line format would be useful?

Yes, there are some CNC machines that need to be driven only by arcs for curved pieces and don't deal with spline curves.


> Maybe tangents of NURBS curve would be exposed to scripting in the future?

I'll see if I can cook up some initial curve evaluating methods for the next beta.

- Michael

Thank you Michael.
Maybe I'll start a new biarc thread.
There is a lot of information on the web.
- Brian

a HUUUHGE wishlist ! obj importer as reference ! similar to Topogun (for Michael ref https://youtu.be/_SOCEnTgSns?t=2m21s )!
where i should have my base Hpoly as reference for modeling, some snaps options to draw curves on Hpoly !
**
i'm not talking about the scripted one that Max did ! (it's making surfaces out of polys - where a poly converted to surface is 16 larger than it should be ->4*4 conversion for a poly) & it's slow, Hpoly wont support, only LP
**
where it can be used !
*scanned surfaces to draw on top of them
*from zbrush sketches to moi - lot's of users will enjoy it ! since poly modelling is Huge time consuming -> will speed up process *4 or more
*there are more obj (meshes) libraries than stl ones !
*u'r stuff :))

- Anti-shell. Instead of shelling out a part, be able to unshell it, essentially making the interior of a part a solid.
- An easier stl import flow. I realize from my earlier posting on the subject that stl import isn't directly supported, but there seem to be workarounds, nothing perfect, but doable (like going through the nodeditor, which I still can't understand or make work, dummy me). I'd love to see something like this incorporated into the next version.
- Parametric MOI!

Hi Cemortan_Tudor, and Bob - these are pretty different kinds of things than what MoI is really focused on doing.

@Cemortan_Tudor - Reverse engineering really needs a specialized toolset to do it well. It's a broad area of work that MoI is just not focused on.

@ Bob -
re: anti-shell, could you post an example?
re: An easier stl import flow - as I mentioned in that other thread, STL files contain triangle mesh geometry, it's a very different type of geometry than the NURBS surface geometry that MoI is focused on working with for modeling. It's also a broad area of work that is pretty different than what MoI is focused on right now.

- Michael

Any chance of adding a angle tool under deformations? If you could simply pick faces then pick the axis to taper from this would really be helpful for making master patterns for casting or models for injection molding.

Right now we are limited to the basic draft from the extrusion tool which is handy for text models but limited to base curves. Often I have models that require more than just a simple extrusion where drafts need to be put in place or modified after creation of the part as features are added. I usually end up extracting curves, offsetting them and lofting them back to create my solids which can be horribly tedious especially when you know the customer is going to make a change for the sake of changing...

Hi KAC - do you have an example you could post? It can be difficult for a deformation to process just some faces and not others.

- Michael

My wish list for MOI4, in random order:
Extend with cursor, without the need for a feature to extend to.
’Snap To…’ - I often want to snap to something that is buried in a blizzard of possible targets- I end up isolating and hiding, but I wish I could just specify ‘snap to the center of this circle’.
‘Look At’ - a feature in other software that lets you select a planar surface and the view orients to it and changes the construction plane to it- I used it all the time, very useful.
An annotation text box where I could keep track of changes I made, things that need to be done, etc.
I’d like to be able to save a high resolution bitmap without shading- my end product is 2d technical drawings that I color with other software- black line art would be great, without going through the gruesome AI file cleanup.
And finally, for now, SVG output. The AI files are a mess- I spend hours trimming/extending/deleting duplicates/etc. Rather than try to improve the accuracy of AI files, a proprietary format owned by a company I don’t really admire, SVG might be a better choice.
I, of course, have no clue about what’s involved in coding these changes- just things that would make MOI better for me.
Rick

I can email a sample model I hand constructed, was a logo that had to go on a pipe that was sand cast. Logo is arched but drafts had to be all perpendicular to the part line.

Look at - try cPlane - orient to all views
Snap to might be scriptable - just for centers of objects
I have a lot of time mess in my scene with snaps options, if scene grows dramaticly -> i have to open several Moi windows to do small stuffs in other windows, keep all tangecy that i need there & one for collecting with few snaps/low mesh angle detail
a saving way for ai I see making a 4k-8k res render of view ( with hight contrast lines ) & trace in ai, manually shade surface inside Ai

when u say reverse engineering - the only thought is hacking that software ! nope ! i wanted a object view inside moi !
obj mesh -> moi
head -> headphones, microphone, gas masc, helm , gear, etc etc - to match shape
table -> ornaments !
old 60'th phone -> ornaments ! details
scanned mesh -> moi
roentgen, room, nature -> objects construct objects inside

Cemortan_Tudor-
Thanks, cPlane is usually a trial and error process- my wish is that a selected planar surface could become the cPlane.
Tracing a bitmap in Illustrator is a lot of work with files that have thousands of curves- editing a Make2D image is the best solution I've found, but still a very long process.
Rick

Hello,

I use MoI for technical illustration as well. You might want to check out the tools from Astute Graphics to extend paths, clean up vectors etc.. That's not to say Moi wouldn't benefit from curve and surface extension features, just a suggestion on what you might use to get by in the meantime.

"my wish is that a selected planar surface could become the cPlane"
cPlane is scriptable