"MoI makes precise models easily without compromise... I dont think precision is an issue.."


Let me just point you here:

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

Hey Nick,
Your link only points to the root forum??? Maybe check the link if you intended to post to something specific.

Hi Nick, to get a link to a specific message, right-click on the link that shows up in the upper-right corner of the message body, like the one here will say 4247.58 - if you right-click that link and do "copy link location" that will get you a link to bring up that message thread starting at that message number.

If you just grab the address from the main address bar that won't work because of how the forum works as a frameset - it's kind of a collection of a few different sub frames.

- Michael

:-| Well, don't I look stupid now.

http://moi3d.com/forum/index.php?webtag=MOI&msg=4215.2

SO you point to a thread where Michael states that someones operation in a model looks like a bug??

Then he gives some explanation of how to get MoI's geometry library to succeed the apparent bug by doing some scaling on the model to complete the operation, then continue on...

The discussion of the internal tolerance settings of MoI is some insight to the process. Some of the commands that do iteration to complete using adaptive tolerances are creating less dense, unwanted heavy geometry.. But it does not mean that The created model is not accurate..

WHat you pointed to was a situation where the command on the model couldnt handle the request at hand due to some possible bug hitting some of the internal workings of MoI, with a solution provided...

This doesnt mean that your 5 inch line may be 4.99 inches long....

Hi Nick, well all NURBS modeling programs have a fitting tolerance that is used for operations that are calculated by a type of refining process, that's not something that's unique to MoI.

MoI generally targets an accuracy of 0.001 units, although I am working on converting to a more adaptable system that will use a fitting accuracy that is some fraction of the object's size which will help to make things work better on little sized objects.

But if you're looking for a system that does not use any kind of a fitting tolerance like that, you'll basically have to rule out every CAD system that's currently in use, since that's just a normal part of how a CAD system operates...

Some CAD systems allow you to specifically set the tolerance to a particular value - unfortunately that often times has a lot of negative side effects, including actually it getting set too loose and making things too inaccurate instead.

But yes, if you have some special need to have manual control over the fitting tolerance you may need to use some kind of special purpose CAD software that has all kinds of intricate settings like that which you may need to attend special training to figure out how to use, lest you set them incorrectly and actually mess things up...

Probably in the future at some point I'll add in a setting that will make MoI target a tolerance of 0.0001 units optionally instead.

Do you have some kind of manufacturing process where you would find a tolerance of 0.0001 units to be inadequate?

One thing to keep in mind is that it is not at all true that more tolerance is automatically better - a tighter fitting tolerance causes iterative algorithms to refine their results more and more, basically causing longer calculation times and also a much larger file size because things like intersection curves will have a zillion control points in them. So just setting the tolerance to some extremely small value is not really a good thing to do, that's something that I've seen as a pretty frequent problem in systems that allow people to set the fitting tolerance to any value at all.

- Michael

And yes that fitting tolerance accuracy only comes into play during particular kinds of calculations that use a kind of refinement process to create their result, like Surface/Surface intersection is one of the main ones.

But for things like entering in coordinates where you're drawing lines and arcs the fitting tolerance does not apply to anything in that case.


So I mean yes definitely the changeability aspect of the constraint systems that MCAD programs offer is definitely useful for editing.

But you should be aware that a fitting tolerance is used in all other NURBS based CAD programs as well - that's not something that's just unique to MoI. If you've assumed that only MoI uses a fitting tolerance and other CAD programs just magically use infinite precision on all operations, that's not correct at all...

- Michael

Solidworks has a rather neat way of dealing with this (if you understand tolerance, that is). If the requested feature or operation cannot be done withing the default tolerance, a dialogue appears showing the minimum tolerance necessary to complete. If you want you can accept the looser tolerance or you can cancel and go back over the model features and find out what caused it.

Maybe this is what Steve refer to : http://help.solidworks.com/2011/English/SolidWorks/sldworks/AllContent/SolidWorks/Core/Surfaces/t_knit_gaps_viewing_selecting_gaps.htm

"""""""""If you want you can accept the looser tolerance or you can cancel and go back over the model features and find out what caused it."""""""""""

Ah yes Steve, and this is the kicker... I have a CAM package that will allow me to set the system tolerance to "15 decimals!!!" If you ask 100 of it's users if it is a good modeler (Capable of making quality solids and surfaces), 96 would say "NO".

Like the abilty to plot the coords for the placement of the b-spline points for the exact curvature of a surface needed at a .0001 tolerance (Instead of having the system do it for you) or recieve poor results...

Has anyone been able to get obj. into the program and been able to work on those or successfully pass then models on to Moi3d
coming from polygons to nurbs .. I am thinking of reverse engeneering....... an Alias program .. Maya does poly to nurbs after all.....???
It also imports Skp ? what for if you cant use them ?
Peter

Import skp works :)
Don't made another try format because no time for that :(

I get a crash with obj as soon as i make another geometry apart from the one imported....
Peter

Hi Peter,
If the poly model is small enough, there is a free utility that will convert an stl to stp.... This will import to MoI as NURBS.. But I have not had success with larger poly sets.

Do I understand you correctly its a polygon to nurbs converter basically a reverse engeneering utility ?
I´d love to know about that !
Peter

Hi Peter,

> I am thinking of reverse engeneering....... an Alias program
> .. Maya does poly to nurbs after all.....???
> It also imports Skp ? what for if you cant use them ?

I don't think this new one has that kind of conversion in it, it seems that you can load polygon objects, but they are a kind of separate object type that can't interact directly with NURBS objects.

So they're more for things like importing a visual reference or something like that and not for actually converting into NURBS geometry.

See this thread on their forum that talks about this:
http://forum.123dapp.com/123d/topics/cannot_extrude_or_fillet_parts_of_an_existing_model


I've heard that Maya does have some kind of function in it for converting sub-d surfaces to NURBS, but it seems that right now the main one that people use for that kind of a thing is the T-splines Rhino plug-in. Also if you use 3DS Max, check out the new nPower converter: http://www.npowersoftware.com/subdtonurbsoverview.htm


I still think it would be cool if the T-splines guys made a simple standalone converter program that could be used for this kind of a conversion without having to buy the entire Rhino + full plug-in combination. Try asking them about that, I've suggested it to them before and maybe if they get enough requests they will cook it up.

Also if you have SolidWorks the T-splines guys have a new plug-in for that as well.

- Michael

I don't test myself but someone say to me that format SAT from 123D to MOI is perfect!
So you can use Free Form or Push Pull / & OR Rotate faces then export to MOI ;)

Hi Petr,

It is here:

http://www.solveering.com/products/products_stl2step.html

The newest version actually works on OBJ instead of just STL.. It converts the poly's to NURBS planes..

It is hit and miss on high polycount models.. Low poly models have worked OK for me.. I had better results with the 1.4 version, but havnt loaded the 1.6 since I changed my OS.. It is a single clcik deploy WPF application, so you may need to be sure you are on windows with the proper .net stuff or something like that..

It's worth a try for what you describe.

Hi Burr,

That sounds fantastic to import some .obj into MoI for modeling reference ...

... but any .obj coming form modo crashs the application :(

Hi PaQ, possibly try triangulating faces first?