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