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Guest tede

Curvature Tools

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Guest tede

The way I understand it is that in Alias and Rhino you can create a circle which has a radius equal to the curvature of any chosen point on the curve.

 

What I dont really understand is how this helps. The only way i have found to use it is to make a note of the radius at the end of a curve i want to align/match too, then align/match a curve to it using normal tools. Then I try my best to match the radii, by moving the points manually. However the same thing can be achieved looking at the curvature combs.

 

Im pretty sure im not going about this in the right way, how do you guys use this and/or other similar tools?

 

Tim

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The way I understand it is that in Alias and Rhino you can create a circle which has a radius equal to the curvature of any chosen point on the curve.

 

What I dont really understand is how this helps. The only way i have found to use it is to make a note of the radius at the end of a curve i want to align/match too, then align/match a curve to it using normal tools. Then I try my best to match the radii, by moving the points manually. However the same thing can be achieved looking at the curvature combs.

 

Im pretty sure im not going about this in the right way, how do you guys use this and/or other similar tools?

 

Tim

 

Not even sure what tool that is (I do as little as possible with curves) so can't help you on that one.

 

You can try looking through the help documentation, may give some hints to it's functionality. Could be one of those things that serves one very specific random purpose for car designers that no one else will ever use.

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Guest Bowl of Soup

Hmm, yeah sounds like you're using a nurbs tool that projects the radii from a given curve point, could you put up some pictures of the tool so we can see what you are trying to achieve.

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Guest solidworm

well the center of that circle is the center of curvature or "instantaneous center of rotation" i don't know how it might be used for surface design but in dynamics, if a moving point with velocity V passes that point, angular velocity(w) of the point will be: w=v/r ; r being radius of that circle.

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I would imagine it being used as some sort of evaluation tool, to see which way your curve bends and how steep.

 

@Cyberdemon: what do you mean you use as little curves as possible? What do you use?

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I would imagine it being used as some sort of evaluation tool, to see which way your curve bends and how steep.

 

@Cyberdemon: what do you mean you use as little curves as possible? What do you use?

 

Some people model very curve heavy. Every surface needs 4 boundary curves before it can be created, manipulation is done at the curve level, etc. This is kind of the work flow for apps like Solidworks too where surfaces are a gap between your curves and other surfaces and thats it.

 

Most of what I do is direct modelling which means most curves just get me to a surface then they disappear. As a result I probably use maybe 1/8th of the curve tools (almost nothing with keypoint curves or blend curves, just 3 or 5 degree EP curves with some fit curve in there).

 

Sometimes I'll just skip curves entirely and start with a plane and start pulling CV's and inserting isoparms.

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Guest solidworm

if this capability was available in ProE, there would be a use for it. i'd use it in variable section sweep command to build curvature continuity between profile and the side surface sections. ProE maintains this relation along the swept path. this way a sweep with G2 connection on both sided could be created.

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Guest solidworm

@Cyberdemon

do you work without history? how do you manage changing the part? i mean if you modify a surface, continuity among surfaces will broke, and you have to redo every surface to surface connection?

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@Cyberdemon

do you work without history? how do you manage changing the part? i mean if you modify a surface, continuity among surfaces will broke, and you have to redo every surface to surface connection?

 

I work with history. History between edge boundarys is preserved, if I align an edge of a surface to another surface, I can modify the un-aligned side of that surface while preserving continuity on the other side.

 

Sometimes it breaks since Alias's history can be a bit of a mystery, but generally when I'm modelling I know theres are few key relationships I want to retain so I know what order of operations to build to retain those histories.

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Guest tede
@Cyberdemon

do you work without history? how do you manage changing the part? i mean if you modify a surface, continuity among surfaces will broke, and you have to redo every surface to surface connection?

 

I work with history. History between edge boundarys is preserved, if I align an edge of a surface to another surface, I can modify the un-aligned side of that surface while preserving continuity on the other side.

 

Sometimes it breaks since Alias's history can be a bit of a mystery, but generally when I'm modelling I know theres are few key relationships I want to retain so I know what order of operations to build to retain those histories.

 

If you dont use curve networks what is there to stop you from getting out of sink with the origional design. In parametric you can always revert back to t the curve to see where you have gone wrong if you catch my drift.

 

How do you know that your model is 'done' (is a model ever 'done'??)?

do you start from some elevation views and you and the designer sit down and talk through the model tweeking till your happy?

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If you dont use curve networks what is there to stop you from getting out of sink with the origional design. In parametric you can always revert back to t the curve to see where you have gone wrong if you catch my drift.

 

How do you know that your model is 'done' (is a model ever 'done'??)?

do you start from some elevation views and you and the designer sit down and talk through the model tweeking till your happy?

 

Maybe I'm confused by what you're asking, but what do you mean by the "original design?"

 

I (the designer) build the CAD surfaces from my own intent (this involves lengthy exploration in 3D, not tracing a sketch or some scanned model data) . It's done when I say it is (or at least when it goes through review and everyone is happy) then the data is imported to Pro E and handed off to the engineers for production and tooling - no rebuilding of data happens on the engineering side to the A surface of the product and it never needs to as long as I build the geometry in such a way that the engineers can do everything they need to with it.

 

If you're referring to me taking a design that someone else did and just pumping the CAD on it, that's not what we use Alias for. We use Alias as a freeform design tool to conceptualize, explore, and produce production quality surfaces for product design.

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Guest JCarruthers
If you dont use curve networks what is there to stop you from getting out of sink with the origional design. In parametric you can always revert back to t the curve to see where you have gone wrong if you catch my drift.

 

Actually working with "curve networks" is, long story short, only one of several possible surfacing workflows, and really not the best for creating efficient, smooth geometry.

 

To the previous question of why model without parametrics/history, well the reason Rhino and Alias exist is for the stuff that's hard to do with the added overhead of a feature tree, for the stuff where you could completely rebuild your model from scratch in Rhino ten or twenty times in the time it takes to build a parametric model.

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I agree, a parametric model is best when you already have a darn good idea of what you want and you're confident you won't stray from that idea too much as you go into 3d, which heh - you rarely do maybe, I can't say.

 

But then again, one could argue you make your concept models with polygons and then jump into a parametric solid modeler to make the final design and skip nurbs altogether? Not that I have done a workflow like that but it's a possibility.

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I agree, a parametric model is best when you already have a darn good idea of what you want and you're confident you won't stray from that idea too much as you go into 3d, which heh - you rarely do maybe, I can't say.

 

But then again, one could argue you make your concept models with polygons and then jump into a parametric solid modeler to make the final design and skip nurbs altogether? Not that I have done a workflow like that but it's a possibility.

 

Not sure what you would gain by a workflow like that. You could argue that it's "Faster" to work in polys (Which depending on what youre modelling probably isn't the case) but you can go directly from NURBS to solids. I bring surfaces into Pro E everyday and turn it into production ready solids.

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Guest tede

@ Cyberdeamon

A friend of mine who was in the car industry gave me the impression that high quality surfaces were done more by CAD guys than the designers as the modeling can take a long time to do and can suck up design time. Hence my question, but i can see that as you are the designer then that blows the question out the water!

 

@JCarruthers

what kind of workflow do you think is the best for creating smooth efficient geometry?

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