Set normal vectors on surface boundaries
Set normal vectors on surface boundaries
(OP)
Hello,
I'm struggling to solve this problem but I need some help because I don't know how to go on.
The problem regards the construction of a couple of surfaces, sharing one edge (in form of a spline curve).
Is it possible to impose the normal vectors of the two surfaces along their boundaries (in particular along the shared edge) on some arbitrary points near the edge?
Thanks in advance!
jones274
I'm struggling to solve this problem but I need some help because I don't know how to go on.
The problem regards the construction of a couple of surfaces, sharing one edge (in form of a spline curve).
Is it possible to impose the normal vectors of the two surfaces along their boundaries (in particular along the shared edge) on some arbitrary points near the edge?
Thanks in advance!
jones274





RE: Set normal vectors on surface boundaries
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Set normal vectors on surface boundaries
In particular, I want to take a set of arbitrary points along the edge shared between two surfaces and then, for each of these selected points, I wanto to set the surface normals for each surface, forcing them to respect those imposed boundary condition (the normal vectors).
I hope I made myself clear.
Here's an image
Thanks again
jones274
RE: Set normal vectors on surface boundaries
Second, are you talking about making these 'vectors' parallel to each other, in other words, are trying to make these surface 'tangent' to each other? If so, have you looked at the 'Match Edge' function?
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Set normal vectors on surface boundaries
RE: Set normal vectors on surface boundaries
RE: Set normal vectors on surface boundaries
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Set normal vectors on surface boundaries
RE: Set normal vectors on surface boundaries
I tried to step back and watch my problem from a different angle, maybe by rethinking the basis of the problem itself.
Since my goal is to find a logic to reconstruct two surfaces, which may be tangent and/or not-tangent along their shared edge, first I have to understand how those kind of surfaces are modeled via the modeler/cad.
In particular, how are the surfaces containing this sort of "fading out" edge (crease) generally modeled in NX by a designer?
To better explain what I'm asking I think it will be useful to post a couple of examples.
Thanks again!
P.S.: I tried also to ask this in another section, since I'd like to understand the generic procedure (valid for various CAD environments) but they had suggested to ask the specific software sub-forums.
RE: Set normal vectors on surface boundaries
The above examples are variations of my example, however, they are all going to be curvature continuous and would probably be a bit more difficult than my example to build due to both the shape of the larger surfaces and the higher level continuity (curvature continuous or G2) - however, the concept of transition is not much different.
Transition.prt
Tim Flater
NX Designer
NX 9.0.3.4 Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB
RE: Set normal vectors on surface boundaries
NX10.0 Win8.1 64bit i7-3770K 16GB QuadroK2200
RE: Set normal vectors on surface boundaries
NX10.0 Win8.1 64bit i7-3770K 16GB QuadroK2200
RE: Set normal vectors on surface boundaries
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Set normal vectors on surface boundaries
The thing I want to do is to understand the common workflow followed by the designers in these type of modeling (creased surfaces, preferrably made with A-class surfs). I've got an educational license for NX so I'm asking in this section: I honestly don't know if NX is the best tool for this kind of surfaces, maybe I've to ask some Alias users.
Meanwhile I whish to thank everybody for the help, this is much appreciated.
Have a merry christmas!
RE: Set normal vectors on surface boundaries
NX10.0 Win8.1 64bit i7-3770K 16GB QuadroK2200
RE: Set normal vectors on surface boundaries
NX10.0 Win8.1 64bit i7-3770K 16GB QuadroK2200
RE: Set normal vectors on surface boundaries
I seriously doubt if Daimler will ditch their preferred styling/industrial design software in favor for NX. GM, FCA (Chrysler) and Nissan all use NX as their corporate CAD software, however all 3 still use Alias for their styling/ID needs.
In 20+ years I've yet to see an automotive company ditch Alias in favor of any of the 2 major softwares typically used as their corporate software. They still import from the ID software into NX. Can't speak for the CATIA side as I've only dealt with Honda and they also import Alias surfaces into CATIA, or at least they did less than 5 years ago.
NX can create Class A surfaces. The issue in doing so is similar to Alias - you've got to understand how to utilize the tools available to properly create the required curves and surfaces as well as how to analyze the results. That's for what the NX Shape Studio product is used.
Tim Flater
NX Designer
NX 9.0.3.4 Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB
RE: Set normal vectors on surface boundaries
NX10.0 Win8.1 64bit i7-3770K 16GB QuadroK2200
RE: Set normal vectors on surface boundaries
Another issue is that the 'Art' schools where most automotive designers are trained almost all use Alias in their curriculums. Granted, we've done a good job of getting NX and our CAE and CAM software into universities here in the US and around world, including many of them who have traditionally supplied engineers to the auto industry, however the designers attend very different and specialized schools.
Now outside of the automotive world, there are a lot of places where NX is being used for ID (Industrial Design), so the basic tools are there, it's just sometimes tradition is a hard act to overcome.
Now some asked whether NX can compete against products like ICEM and Alias, and while we think we can, we have to also choose our battles. While it may not appear that we've had a lot of success competing for the limited number of seats in the various auto studios, we feel that we can offer a viable solution for the small to medium sized companies, or even some larger ones, who are looking to add ID capability to their organizations who are already using NX for CAD/CAE/CAM but who have not used any dedicated styling software in the past like ICEM or Alias. Potentially there are a larger number of seats available to for us to win than what is currently in use by the automotive OEM's. This is the market that we've positioned products like NX Shape Studio with it's new 'Realize Shape' tool as well as the work that we did in rendering for NX 10.0 and what we're continuing to do in NX 11.0.
To learn more about what I've commented on above, please go to:
http://www.plm.automation.siemens.com/en_us/produc...
And please check-out the list of 'Case Studies'.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.
RE: Set normal vectors on surface boundaries
NX10.0 Win8.1 64bit i7-3770K 16GB QuadroK2200
RE: Set normal vectors on surface boundaries
Not only is Alias being taught to the IDs, there is probably not as many NX users out there that can fully grasp the Class A tools available in NX unless they've come from an ID background. It's not something a typical user can sit down and fully teach themselves like they might be able to do with the more often used modeling tools outside of Shape Studio and Realize Shape. You've obviously been exposed to Class A modeling and the workflows that are sometimes used, so you can imagine the difficulty in trying reteach yourself those dark arts in a different software. Probably not an easy task.
Software choices in many industries is a great and interesting topic, especially when you're able to watch how things have changed over the years. Who would have thought that the former UG would "merge" with SDRC (in terms of software); Autodesk acquiring Alias; CATIA gaining ICEM, etc.
Tim Flater
NX Designer
NX 9.0.3.4 Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB
RE: Set normal vectors on surface boundaries
The artsy folks are creating concepts. These concepts don't necessarily need to be realistic, and sometimes they are deliberatly unrealistic -- the stylist creates a "caricature" to emphasize some aspect of the design. The geometry created in this phase is not subject to any feasibility constraints; it just has to look nice. So, it doesn't matter too much if the shapes are too expensive to manufacture, or the engine won't fit under the hood, or the A-pillars are too thin to support the roof. The geometry is not used for much, beyond the concept evaluation phase. NX can be used to do this sort of work, but the guys doing it don't like to think of themselves as "CAD users", and they probably learned Alias in art school, so NX isn't used much. The market is small, so Siemens probably doesn't care very much about the artsy crew. Though I guess you could say that NX "Realize Shape" is an artsy tool.
Production "class A" surfacing (or "class 1" surfacing, at Ford) is an entirely different game. The geometry is real, it has to satisfy numerous different constraints (in addition to looking nice), and it is used to produce dies and structural body parts. For a long time, ICEM/Surf was the tool of choice in this area. A few companies use Alias, a few use Catia. Toyota and Honda both use internally-developed systems. There are numerous auto OEMs who use NX in this area. I can think of at least two that have switched from ICEM/Surf to NX. As one of the other replies mentioned, there is significant benefit to using the same system in production class A surfacing and in downstream engineering/manufacturing, so the companies who use NX for all of this are typically happy.
The "surfacing" software business does not appear to be a very good one. Lots of systems/companies have gone belly-up. Remember STRIM, and CDRS, anyone? The ICEM/Surf group has been bought and sold umpteen times, and I don't expect Think3 to last very long. Alias got bought, too. Rhino seems to be doing nicely, but it will die if SolidWorks ever gets decent built-in free-form functionality. The problem is that the market is small, but Alias has to have all the same basic infrastructure as NX or Catia -- graphics, UI, saving and opening files, translators, print/plot, etc, etc, etc. So, high fixed costs, and small volumes. The only way out is to charge high prices, which people are increasingly unwilling to pay.
RE: Set normal vectors on surface boundaries
To compliment BubbaK's post, maybe the most intriguing acquisition is the Autodesk buying Alias, considering that Autodesk already owned 3DStudio Max and Softimage, and subsequently has bought Delcam.
3DStudio and Softimage ( and Maya which was a part of the Alias acquisition) are more intended for game development / image rendering than product development, but all 4 (5?) are also capable surface modelers.
(Softimage has since been terminated)
Back to the original question.
trying to actually design something by assigning vectors ( or angles) along an edge like that is like trying to find the matches in the darkness, difficult. - It's hard to guess what angle or vector will look good.
But, NX does more or less have this function, as a part of the Law extension surface .
Attached is a version of the part Tim uploaded, with both methods included. (My version is quite different from Tim's.) NX10.
The Law extension example is eyeballed towards the spline used in the upper example. The angle is ...
Regards,
Tomas
RE: Set normal vectors on surface boundaries
As the previous reply indicated, NX has functions like Law Extension that let you control angle variation. But I doubt that you know what the desired angles are until you see the result and confirm that it looks good. In other words, the correct angle is an output of the design process, not an input.
The ICEM crowd would create this shape by pulling control points (poles) around. In fact, they do everything by pulling poles. So ...
(1) Create a simple surface (one patch, degrees of around 2 x 2).
(2) Split it into four patches, call these p11, p12, p21, p22.
(3) Modify the poles of one patch to produce the non-tangency, while keeping the other 3 joins tangent.
The trick is that moving poles that are two or more rows away from an edge will not affect the edge normals.
(4) If you need a more complex shape, gradually increase the degrees to give yourself some editing freedom. But, the more freedom you give yourself, the more difficult it is to keep the surfaces smooth.
RE: Set normal vectors on surface boundaries
@Toost: this might be EXACTLY what I'm looking for!! I'm new to NX and didn't know the Law Extension command: I'll start to study it in detail, but it seems it permits to do what I intended to!
@Bubbak: In facts, I have to develop a procedure to impose some angles before building the two connected surfaces.
However, if I understood well, the coomon practice of style designers is to build nice surfaces without bothering with angles, vectors or, in general, without following a "parametric" approach. Is this correct?
Thanks again for your help!
RE: Set normal vectors on surface boundaries
in most (?) cases a design starts as a sketch on a piece of paper where the proportions , the "expression" and the "style" is captured.
Then somebody will transform that into a computer model.It might be the designer or a different person.
the computer model will then be iterated into the final product and during these iterations the "parametric approach" is very valuable, but trying to describe the shape of a car fender in numbers, is... difficult.
Regards,
Tomas
RE: Set normal vectors on surface boundaries
In a larger sense "parametric" might mean "driven by parent-child relationships" (though "associative" would be a better word). This sort of "parametrics" can be very useful in production surfacing. It's nice to have your fillets updated automatically when you move your base surfaces, for example. The automatic update might not give you exactly what you want, but it will still save you some time. In fact, this is one of the reasons that some people prefer NX; systems like ICEM and Alias are not very good at associative relationships.
In your example, I'm still not convinced that entering angles is a good approach. Moving poles allows much more flexibility. But, you understand your task much better than I do.
RE: Set normal vectors on surface boundaries