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From: Michael Gibson
Hi Bravlin, that looks like a bug, I will investigate.
You can add a point by knot insertion instead of control point insertion though. That's when you click directly on the curve instead of on the control polygon. It's easiest to do that if you have control points turned off when you are in Add pt and then click on the curve. That will refine the curve in that general area without changing the shape of the curve.
It's normal when adding a control point to the control polygon that the shape of the curve will change a bit but the new control point is not supposed to shoot off like that.
- Michael
From: Michael Gibson
Hi Bravlin, the bug has to do with the curve being a rational curve which means it has additional weight values in addition to the x,y,z coordinates for every control point. Usually only exact conic section curves like arcs, circles, and ellipses use weights. This one probably has them from combining an exact arc with a neighboring curve.
I'll see if I can get it to behave better.
- Michael
From: Michael Gibson
Hi Bravlin, yes it was a bug in handling inserting control points into a rational curve that has weights. It's fixed for the next v4 beta, thanks for reporting it.
- Michael
From: Bravlin
Q_03: Hope it's not too much if i ask 2 questions one day. Got another shape-question.
We discussed earlier the network-operator approach. And for smooth shape it works great.
But today i tried to use this approach to construct this shape. This shape a bit more complex but still have rounded sides.
I spend half of a day in attempts to create clean shape and generate plenty of guesses in a process.
So if it possible can you share some guides rules to network operator according this shape.
I attached project file that have 2 layers.
On layer "L_09" i trimmed profile curves in direction of middle line, and on layer "L_10" i trimmed it in axis direction.
But i guess since we have shape that do not have equal sides its not an issue.
In result we should have something similar to that shape.
Attachments:
MQ_005.3dm
Image Attachments:
PIC001.png
PIC002.png
From: Michael Gibson
Hi Bravlin, sorry I'm not fully understanding your Network question. Is it that you would like it to make a shape as if it had already filleted edges in one single application of Network?
That will be difficult since Network builds one single surface result (which will be split up at any sharp corners) and it is difficult to make a single surface that goes through a localized significant change in shape like a fillet transition.
In general it's best to use Network to build one smooth surface which has a regular 4 sided boundary. It isn't generally very workable to try and build what should be a multi surface model out of one single Network.
Over time I have noticed a kind of recurring pattern that people with a poly modeling background really like to draw all the 3D edges of their model and then want to use Network to fill it in. But with NURBS modeling usually it is better to make extended pieces that do not have pressure applied to their boundaries, that's how you get high quality surfaces. Then some of your final edges come from intersections like trims or booleans rather than trying to do it all with directly constructing surfaces to an irregular boundary.
- Michael
From: Bravlin
Michael thanks again for your answers. Hope i not too annoying you with this those nooby questions.
Such small fillet is not required, its better if rounded edge would have wider angle. It would be hard i guess to mimic that fillet result via Network operator.
I just want to understand the logic and rules that network use. I can't understand what exactly cause the problem with this shape.
- Is it a center spot that i used to divide edge profiles on equal parts.
- Or its an angle that i choose to divide profiles.
- Or maybe the different number of points in rail profiles.
- Or its maybe a sharp points in curves.
- ... etc.
I now know how to build rounded shapes like those that we build in Q_01.
But for more square like shapes that also have smooth edges and tilt (so they not easy to trim or extrude) i still don't know what to do.
The trim approach and extrude creates sharp corners and i need this shape as one piece(or 2 mirrored pieces).
The result shape on a picture is a combination of extrude, trim and loft. But if you look on it, shape lack of continuity and smoothness on edges.
That's why i want it in one piece. I know that for such shapes it would be easier to make it in polys and import to moi.
But i want to learn the cad approach and its limitations.
From: Michael Gibson
Hi Bravlin,
re:
> I can't understand what exactly cause the problem with this shape.
Well a few different things - too much variation in shaping between stations, like you have tight bends in the corners and then those collapse down to a pole point for the next station. There shouldn't be so much variation between profiles.
When collapsing down to a pole it's best for the shape to resemble a circle before the pole, something more like the attached file. But overall it's not a feasible shape to try and do with one single surface with poles.
Little skinny pieces are because of sharp corners not being aligned to the other direction's curves:
> The result shape on a picture is a combination of extrude, trim and loft.
> But if you look on it, shape lack of continuity and smoothness on edges.
Can you post the model file so I can get a better look at it?
> But for more square like shapes that also have smooth edges and tilt (so they not easy to
> trim or extrude) i still don't know what to do.
You build an extrusion that is straight and has flat ends initially, then introduce tilt by cutting it with a side profile, something like:
- Michael
Attachments:
MQ_005_2.3dm
Image Attachments:
BravlinNetwork1.jpg
BravlinNetwork2.jpg
Bravlin_boolean1.jpg
Bravlin_boolean2.jpg
Bravlin_boolean3.jpg
Bravlin_boolean4.jpg
From: Michael Gibson
And if you wanted to fillet it you'd also generally avoid building these tight bends into the profile to start with, since that will limit the fillet to have to be smaller than that tight bend to avoid bunching up on itself:
- Michael
Image Attachments:
Bravlin_boolean5.jpg
From: Bravlin
>you have tight bends in the corners and then those collapse down to a pole point for the next station.
Sorry i am not sure if i understand it right. I tried to understand what you mean from project file you provide, but i don't understand what those circles mean.
Oh maybe you mean this difference in shapes ? Yes the profile in center should have the shape of a rail curve flatten.
>Little skinny pieces are because of sharp corners not being aligned.
How they should be aligned ? I checked all profile curves (except rails) to doesn't have tilt.
I also tried to build them such a way so they touch rail curves with control points but it doesn't help much.
I attached a project file with result shape i construct with extrude, loft, shamfer and fillet.
> But for more square like shapes that also have smooth edges and tilt (so they not easy to trim or extrude) i still don't know what to do.
This one in result have sharp edge here.
And if you try to create tilt on a rounded corner part by trimming or extrude you lose roundness.
You may create loft surface (not solid) and boolean-merge it. But the result edge that connect loft part and extruded part also will be sharp.
Attachments:
MQ_0051.3dm
Image Attachments:
PIC003.png
PIC004.png
PIC005.png
PIC006.png
From: Frenchy Pilou (PILOU)
About your first post for this object...
If they are not some "patch" or functions (Trim etc...)will be impossible... ;)
From: Frenchy Pilou (PILOU)
Else before some deformation cage :)
We "Separate" a surface (s) from a volume and we "Add points" to it (Edit Menu / Add Pts)
This makes it like a deformation cage where you just have to move the Control Points!
Points can only be added on one surface individually!
However, you can then move the Control Points from several surfaces at once!
Edit / View Points function activated of course! You can use the Edit / "Hide" and "Lock" functions
At the end, everything is grouped into a single "solid" volume (if the points of each adjoining face are "confused"!
For move points with some mirror effect with Scale function ;)
From: Bravlin
At first i create profile curves that lies exactly on rail curves.
But its not the main problem. The result shape looks messy.
From: Michael Gibson
> >Little skinny pieces are because of sharp corners not being aligned.
> How they should be aligned ? I checked all profile curves (except rails) to doesn't have tilt.
They should align by the curves touching each other at sharp corner areas.
Currently the closest points between your curves in that area is here:
So the generated surface is going to match up the closest points between those curves, and since that is not at the sharp point that will make a skinny fragment there when it additionally passes through the sharp area.
> I also tried to build them such a way so they touch rail curves with control points but it doesn't help much.
Touching control points is irrelevant, it's the actual body of the curves that would need to touch.
> And if you try to create tilt on a rounded corner part by trimming or extrude you lose roundness.
If you want your cut to have roundness you could build a rounded cutting surface using something other than extrude, like sweep. Then you'd fillet sharp edges to round them off.
But if the type of work that you want to do is similar to chipping away fragments of an initially blocky object while keeping everything smooth, that's really something more suited for ZBrush or 3D Coat's functionality. It's not a great fit for NURBS modeling.
- Michael
Image Attachments:
BravlinNetwork3.jpg
From: Bravlin
Michael,
so if i understand it right there no need to create curve profiles so they lies with control point exactly on a rail profile.
You just need touch it somewhere(in other words you need intersection).
Mr. PILOU,
and there is no smooth operator plugin or script and no brushes for Moi right ?
Only click and drag points ? Maybe there is a grow selection script for points like we have for faces ?
From: Michael Gibson
Hi Bravlin, yes for the case of having sharp corners, the other direction curves should intersect with the corner location.
On other cases where there are not sharp corners it's usually ok for the curves to just come close to each other.
But that's just one issue - it's still just not going to work very well to try and build something like that out of one single network surface.
- Michael
From: Frenchy Pilou (PILOU)
<< Smooth operator
I believe that a nurbs surface is by definition a "smooth" surface :)
If you want modify it use my method above or similar and use some moves of the Edit Frame with some Control Points selected
<< No Brush
I don't believe for the moment
<< Grow Selection
for the moment only for faces from Edge or Face by Max Smirnov
A radial selection will be a fine start ;)
From: Bravlin
> I believe that a nurbs surface is by definition a "smooth" surface :)
Nice one ;) We still need to move control points to make surface smoother.
Something similar to smooth deformer in XSI or a brush that distribute parameter (smooth deformer weights) could be pretty helpful.
From: Frenchy Pilou (PILOU)
<< We still need to move control points to make surface smoother.
Maybe there is yet something with the Node Editor! Ask it on their thread!
https://moi3d.com/forum/messages.php?webtag=MOI&msg=7777.1
(but your are not on the Nurbs' spirit ! ;)
From: Michael Gibson
Hi Bravlin, often it is not feasible with NURBS to smooth things out using control point editing because of how trim curves and "underlying surfaces" work.
When you do a boolean operation, surface control points do not change at all, instead the trim curves on surfaces are what changes. Trim curves mark areas areas of a surface as holes and in a model with trimmed surfaces you generally can't manipulate surface control points without opening up a hole.
There is some illustration of that here:
http://moi3d.com/faq#Q:_Why_does_show_points_work_for_some_objects_but_not_others.3F
It's a very different type of structure than polygon modeling.
- Michael
From: Bravlin
So that's why boolean great in NURBS and such a crap in poly modeling.
So the more NURBS-like approach is to build shapes like so ?
Create profile curves, extrude curved surfaces, manipulate points (in this example i
use flow as deformer to bend surfaces) to get shapes you want. And trim it in the end.
Attachments:
MQ_03.3dm
Image Attachments:
PIC007.png
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