Hi Burr,

> Although called "sweep", it seems to be more "Rail Revolve"
> that the input curve is drawn while in the command.

What if you want to use some curve you have already previously drawn instead of drawing a new one, is there any way for it to do that, or does this particular command in Amapi actually _only_ work with points that you then pick after launching it?


> So , pick the rail (the circle to start with) then the command
> is waiting for the pick points. the revolve surface is drawn in
> with each pick.. No 25 curve commands... Just utilizing curve
> through points as a method.

So it's only fixed to use just that one particular "through points" method and not any other kind of curve drawing method? What if you want to make some lines and tangent arcs in there or something like that, are you just out of luck?

- Michael

Hi Michael,
Well, when you launch "sweep" in Amapi, you get a subset of 4 options. One acts like "Rail revolve" where you have to have a rail and then the profile curve already drawn.. Another is the "Sweep" which is what i showed. Another is "Extrude" which maintains the base shape and rotates as the extrude is picked..

""""""So it's only fixed to use just that one particular "through points" method and not any other kind of curve drawing method? What if you want to make some lines and tangent arcs in there or something like that, are you just out of luck?"""""""""""

No. Then you use the other methods where you pick the paths, just as in MoI.. This is more a dynamic, while drawing to operation. Although the "Through points" dynamic part seems to be fixed..Luike you cant change that to be "control points" type picking.

The extrude also continues as if it was a "Curve through points" picking method, until the command is ended.. I guess this seems like something underlying in the commands that was written in and that I was looking to see if you could get into MoI...

I'll make a video to show the tool in action and demonstrate what i was refering to...

Hi Burr,

> This is more a dynamic, while drawing to operation.
> Although the "Through points" dynamic part seems
> to be fixed..Luike you cant change that to be "control
> points" type picking.

That's the part that seems strange to me - that particular dynamic method sounds like it is limited to only draw a curve one in just that one particular way, by through points only. A lot of times that's actually a worse way to draw curves than control points because it tends to be easy to make kind of bulgy and wiggly shapes.

It just doesn't make a lot of sense to me to make such a kind of hard coded "one drawing method only" mechanism like that, it's lacking in flexibility.

I guess that it could be possible to make a specialized different command that would do that in MoI though (pick some points and build a curve and do a revolve on every point pick) - having it hard coded to just work with one kind of drawing method would make it a lot easier to implement as a plug-in. But it would be a lot easier to do it as some kind of new special purpose command rather than trying to incorporate it as some kind of option within the existing Sweep command.

- Michael

It just seemed how all the box modelers are working... So kindof emulating those in a NURBS sort of way..

Hi Burr,

> It just seemed how all the box modelers are working...

Not quite though - box modeling tends to work by extruding polygon faces, kind of punching an existing face outwards into a protrusion and optionally shrinking or expanding the end of it.

That's a pretty different thing than a "draw curve" / revolve type method like you've been describing.

- Michael

I guess my wording kindof confused it a bit.. You watched the video I posted? It's not drawing curves or anything.. I just drew the circle then selected it and started extruding it out.. At different points, I click to set the shape and continue on.. Just like Box modeling only on the NURBS curve and not a polygon face.. I guess it's hard to tell from a quick video with no description of what is happening..

Hi Burr, yup I watched your video - but box modeling is not normally like that, it's more about punching out different polygons to make bumps and protrusions to add smaller details to a simple initial blocky shape.

The method you're showing is not like that at all, you're not adding in local details or stuff like that (local meaning just in one small area of the model and not doing something that spans the whole circular area of the revolve), you're making one large shape there...

- Michael

Hi Burr, so another way to describe it is that "box modeling" usually means you actually start out literally with a box and then start dicing up some faces and then pull some of those faces outwards to make new protrusions to make things like arms, legs, etc...

The video that you were showing is not really very similar to that method, you're showing making a new surface of revolution starting from nothing by picking some points to create it, not modifying a box like box modeling.

- Michael

Well, there is the limitation of working on "curves" and not surfaces.. I suppose I could collapse this NURBS object into a poly object and start pushing and pulling little segments around...:o

Although, since i am working on NURBS surface, I could trim up the surface to have little edges to work with.



I could cut little eyes and lips and things, then grab those edges and box model some little detail there....

@ Bur : you were right :) My memory is some false :)
In Amapi
In Nurbs Mode you can Stretch / Extrude with just draw "the green line" and the red nurbs surface is automatically dynamically drawn at each new move / clic point :)
But I suspect that Polygons are under for screen drawing (you can see edges ;)
here a "circle" selected for extrude / Stretch (in the same time)
Stretch = vertical move
Extrude = horizontal move
Green line is the active path drawing between each clic or move of the mouse

Hey Frenchy.. Yeah, I was wrong on the "through points" extruding also.. Seems it is "Control points" that is being used...

Really though, it is nothing we cant do in MoI.. It just seemed to me that many people work in this method.

I'll attach a little shot of what i just did that shows why I called it box modeling in a second..

Hi Burr,

> Well, there is the limitation of working on "curves" and not surfaces..

Yes, but that's one reason why what you are showing is pretty different from "box modeling"...

You're showing something I'd describe more like "freeform tube drawing" - box modeling is a different technique than what you've shown in either of those videos.


> I could cut little eyes and lips and things, then grab those
> edges and box model some little detail there....

If you would like to work in that way you might want to use a polygon modeler for doing that, they've got a bunch of tools in them that are more specifically oriented around that stuff.

The other part that goes along with that is sub-d smoothing which is a part of box modeling, the box modeling creates the sort of outer hull and then sub-d smoothing is applied to it to make a kind of smooth melted down shape out of it.

- Michael

Hi Michael.

I added the little video to show why I called it "box modeling"..

""""""""""If you would like to work in that way you might want to use a polygon modeler for doing that, they've got a bunch of tools in them that are more specifically oriented around that stuff."""""""""""""

The dicing it up was just in response to you pointing out that i couldnt "pull little bit's around to make detail.." I do have some poly modelers to use.. It works with any little bits of curves and edges.. Not just circles or tubes..

Hi Burr,

> The dicing it up was just in response to you pointing
> out that i couldnt "pull little bit's around to make detail.."

Well I kind of meant more while you were still within that dynamic extrude tool, you had to add in some other tools to the mix like drawing in some other curves and projecting or trimming stuff with them.

But you're still not quite getting the same effect as box modeling with your latest example there because you've constructed something made up of separate surfaces and there's a hard creased edge where the surfaces touch.

One of the parts of box modeling is that when sub-d smoothing is applied all the protruded pieces all smoothly melt together.

In your hexagon example (where you were doing actual box modeling), if you switched to pull out just one top face after having pulled the front out, you'd get a kind of non-tubular shape with a lump just on one side but that was still all smooth which would be hard to replicate with your other method of just building several NURBS surfaces from curves projected on to a main body piece.

- Michael

Hi Burr,

> It works with any little bits of curves and edges..
> Not just circles or tubes..

Right, real box modeling works like that, but not the "dynamic NURBS extrude" that you've been showing, that builds a kind of individual tubular surface for each separate time you use it.

That's kind of "bunch of little tube surfaces next to each other" is not really quite the same thing as poly box modeling - the real box modeling ends up with an all melted smooth sub-d surface across the whole shape.

- Michael

Yeah, for the NURBS I would have to follow up with fillets and blends and things... I didnt think it would be a replacement for a SubD program..

Hi Burr,

> Yeah, for the NURBS I would have to follow up with
> fillets and blends and things...

Yup, but depending on the situation it can be hard to put blends in on things that are branching in multiple directions nearby each other or also on areas where the protrusion is more of a broad wide area making it more of a shaping to the base object rather than a little tube coming out of it.

The other thing is that drawing a curve and using it to trim or project a hole is a much different kind of a step than box modeling, but one which is a big advantage to NURBS modeling for mechanical shapes since you can cut a precise hole anywhere you want in a NURBS model but in box modeling you have to try and manually arrange a bunch of vertices from the base shape into the shape of your hole.

- Michael

Well, we wont be making the 3 tools, Extrude/Sweep/Revolve, Dynamic! :o

Hi Burr,

> Well, we wont be making the 3 tools, Extrude/Sweep/Revolve, Dynamic! :o

Maybe in the future as some completely separate plug-in command, but it's hard to see how to make it work by modifying the existing command.

Among other things mentioned above, it would probably be pretty awkward to try and fit in a checkbox in the UI that totally changed a command's behavior.

Like with Revolve for example the normal way that it works is that you pick the revolve profile before you even start the Revolve command. Adding in a checkbox that would then ignore the selected profile and let you pick some points would be pretty weird, like what would happen if you then unchecked the checkbox, would your picked points disappear or something like that?

Just the sequence of actions that you are talking about doesn't really fit in with the existing commands, for the kind of "dynamic revolve" like you are talking about you want to have the points picked to define the profile _after_ the revolve axis is set up, it's opposite of the current revolve workflow. It's hard to reconcile such opposite sequences as checkbox options within just a single command - with a totally separate command then it's more feasible.

- Michael

And other thing ;)
appeling creation function in Nurbs mode is some bad
that avoid to think about the generator curves ;)