Hi Michael,

I can't express how much i appreciated the way you explained the concepts about which I asked you.
Thank you very much!

More or less now all is clear in my mind, regarding the way Moi deals with the tolerance, and also, as a result, the way Rhino does it.

So, given everything that you told me, i want to ask you the these questions :

Now, let's say that i have to do a science fiction movie, and i want to model all the involved "actors" in Moi and Rhino,
and as final stage, animate all in a dedicated animation software, like Modo or Lightwave, or also Rhino with Bongo for very simple animation.

Given that, let's say again, the actors are a spaceship fleet, varying in size in the range of 10-100 meters, and a planet sized like the Earth.
What's a real good modelling workflow ?

Model the spaceship fleet and the planet in two separated stages, that is, two distinct .3dm files ?
But, in this case, how can i place all the objects together in any scene ?

Or did you mean that not with Moi nor in Rhino, is possible to do that ?

So, what i have to do in this situation ?
Maybe export all the objects in .obj format and only then i'll be able to assemble all the actors, in order to do the movie ?

If so, that means that the objects in .obj format can get rid of the tolerance, while until i'm working with nurb objects i always have to think about the tolerance ?

I'sorry if i ask you so many things, but if i don't gain in these concepts, it's as i'm swimming in the mud :)

Thank you very much again for you patience and good job!

Marco.

Hi Marco,

> Given that, let's say again, the actors are a spaceship fleet, varying in size in the
> range of 10-100 meters, and a planet sized like the Earth.

I guess I'd recommend only modeling the spaceships in a CAD program like either MoI or Rhino, and create the planet only inside the animation program and not in CAD at all.

Or maybe you could render the planet separately using different unit scales for each in the modeles, and composite the renders together rather than trying to model the planet using the same units as your spaceships.

I'm not sure which way would be the best, you'd probably have to try a couple different ways. In some ways the animation programs will be less sensitive to tolerances at least at modeling time because they usually don't do operations using iterative solvers like CAD programs do where they refine a result like an intersection curve until it is within the target tolerance level. But with rendering as opposed to modeling there can still be tolerance issues in the animation program as well for stuff like bias factors in ray tracing where the start point of a shadow ray has to be moved slightly above a polygon so it doesn't hit the same polygon it's coming off of and result in self shadowing. Often times that's a fixed distance value and might need to be set to different values that are relative to the scale of the objects being rendered.


> If so, that means that the objects in .obj format can get rid of the tolerance, while until i'm
> working with nurb objects i always have to think about the tolerance ?

You may still need to worry about tolerances at render time if there are things like bias factors involved. You should probably do some simplified test runs using different methods to see if there are problems or not.

- Michael

Michael, thank you very much for your recommendations and for your suggestions !

> But with rendering as opposed to modeling there can still be tolerance issues in the animation program as well for stuff
> like bias factors in ray tracing where the start point of a shadow ray has to be moved slightly above a polygon
> so it doesn't hit the same polygon it's coming off of and result in self shadowing.

Thanks for reminding me the existence of the "Trace Bias" involved in the calculations of the shadows inside of ray-tracing software. :)

> I guess I'd recommend only modeling the spaceships in a CAD program like either MoI or Rhino,
> and create the planet only inside the animation program and not in CAD at all.
>...
> I'm not sure which way would be the best, you'd probably have to try a couple different ways.

I'm going to do what you suggested in order to investigate the different approaches, and to experience at first hand the different results.

Thank you for all, and have a good night.

Marco.