Hi Michael



When I said behave better again that was because when I attempt to use booleans with open surfaces, they mostly would perform as trims - trying it now, I took two open surfaces, did a boolean add - the two surfaces are still separate and there's a little piece that I needed to delete that would have been removed if these were solids.

You've now explained to me that trims are used for surfaces - at times I was still using booleans hence my impression about solids being preferred over surfaces within MoI.

There was also the issue with the surfaces normals for open surfaces that added even more reinforcement to my perceptions.




...And this is what I needed to know and why I asked - as far as my experience with NURBS, it has only been though Rhino up to v2 and now MoI.

Now I did perform a test yesterday, exporting two joined surfaces into Cinema 4D - all the normals were in the proper direction, but the app I really need to test is Lightwave since that's the one that exhibited the flips the last time I ran across the issue.



Never had the idea at all since my experience is now mostly with MoI - if that is a problem with other NURBS modelers, now I know.



Here you've totally misunderstood my post.

I have a full understanding of NURBS surfaces and solids - that things need to be joined to be water tight I would never expect to just butt two surfaces together and expect them to be implicitly joined while modeling or during export. I wasn't saying that in my post at all.


I'm sorry if you felt or it appeared that I was attacking MoI's capabilities, I was really just wondering if it was now okay to boolean and export open surfaces.

Looking back at my original post:



What I was saying here was that it appeared easier for him to join surfaces - making an assumption that he was using bools (I didn't notice any separate trim/join - but that's not to say he didn't do that.)

By freedom I meant it appeared that joining surfaces was a single step operation as it is now for MoI with solids.

Finally my question to you was:


Which was asking would booleans for open surfaces ever be as easy as with solids (from my impression in the video) and will the normal directions (be fixed) when exporting surfaces.

You've informed me that trims & joins are the methods within MoI for working with open surfaces and that fixing the export normals for open surfaces is something that's not possible and that all open NURBS surfaces would exhibit flipped normals.

There's my answers...

-Will

Hi Will, thanks for clearing that all up - I didn't really think you were "attacking" MoI, it just seemed like you had jumped to a variety of assumptions, maybe because things happened to be named differently in MoI than what you had seen in that other video or stuff like that.

Also I have definitely steered people towards working with solids while they are modeling, but more because it can save a lot of time, not because it is absolutely "required".

- Michael

Hi Will also one other note:



Also when you join pieces together, what it will do is give you a _consistent_ normal between each piece.

However, unless it has joined all together into a solid, it is possible that the whole piece may not have the normal direction that you want.

That's something that happen in any 3D app where you are not working with closed objects, including polygon modelers as well - it's why there is a flip function in all polygon modeling programs.

If you have everything closed up into a solid, then again one of those convenience features kicks in and MoI will know how to automatically orient things to the "outside" of the solid. But if you do not have a solid MoI (and any other 3D program really, including NURBS and polygons as well) does not have any good way to know which side is supposed to be the outside.

So if you work with open objects in MoI instead of solids, you may need to flip your object at some point, either in MoI (set up a keyboard shortcut and put in Flip as the command name), or more likely in your polygon modeling program where the normals have become important to you.

But again that is not something specific to MoI - any 3D modeling program that works with open objects may require flipping at some point because it is not generally easy for software algorithms to recognize which side of an open mesh is supposed to be the "outside" part, since there is only a clearly mathematically defined inside and outside with closed objects. Without it being clearly defined, it tends to require human judgment to say which way they are supposed to go and it is difficult to emulate human judgment in software.

But Joining will still help you significantly because it will make the whole joined piece at least have a consistent normal throughout it, so that individual sub-pieces of the joined object do not need to be flipped independently, just the whole thing may need flipping still.

The only way you can avoid the need to potentially do any flipping at all though is to make solids before exporting the mesh - that's the case where it is handled for you automatically.

- Michael

Hi Will, so just an example with flipping...

Say you are in a polygon modeling program and you create one polygon like this:



Then you add a second polygon here:



And then a 3rd one here:




At this point you have a mesh with 3 polygons. It does not necessarily have its normals oriented towards what now appears as the "outside", you may need to flip it. It depends on how the first polygon was drawn and what direction it happened to start out with.

The polygon modeler doesn't really understand that the first created polygon was supposed to be the front face or the back face or whatever of the final object.

The same thing will happen when working with NURBS surfaces as well - it's not something that is a bug to be fixed, it's something that is part of working with open geometry in any kind of geometry system.

So it is not unexpected or abnormal or a bug that you may need to flip open pieces, it's an expected part of the workflow.

But if you work with solids, it is another thing that you can avoid worrying about because it then does get handled for you.

- Michael

Paolo wrote: "I used SolidthinkingLt and the update(Forma) a few years ago, and it crashed all the time..."

Same experience here. I once spent a few weeks thoroughly testing ST as i wanted a parametric modeler to complement Rhino. To me, it was then (and probably still is) the most similar parametric system to Rhino (and now to MoI) in the overall feeling. But stability was always an issue. Even simple history modifications would often crash it. I will give ST developers some credit as it has some really cool features such as point editing a surface and not breaking history from the input curves. But then there are other things (those things which may be done 20 times in a session) which are so much more complex to do than in MoI or Rhino.

jonah