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aproximate copy of SURFACES?

TobiasLarsson
8-Gravel

aproximate copy of SURFACES?

I asked this question on mcadcentral recently, but i haven´t got a solution for it yet so here we go:


Is there any way you can copy a couple of quilts to get a single quilt surface? (like when you copy some curves, and pick approximate and get just one curve) .

I found that you can make a copy of a couple of surfaces, use offset and under "options- special handling" set the quilts to be apporximate and get a result that is "one single surface". The problem there is that i have to set a value for the offset , it cant be "zero" (and also that it behaves a little funny sometimes) .

So, is there a way to get an approximate surf? Or just a way to connect quilts to be one single quilt.

//Tobias

Ps, the reason i want to do this is because when i´m patterning something that goes over a few quilts, it sometimes becomes very unstable and may fail if the quilts changes shape...


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22 REPLIES 22

Default offsets at zero work better than anything else. Not sure why you cannot use zero.

Older Creo 2 releases had some serious patterning problems.  Knowing that, I am still on M040.

Look up Copy Geometry...

...or resort to importing an IGES saved version.

Everything PTC is known as "touchy"... but never unstable

Thanks for your answer, but a default offset at zero give me nothing else than a regular copy so that won´t work since I want to get a single patch surf. ( and i could live with the fact thats its an aporoximate surf as long as it dont deviate to much from the original) Regarding copy geometry, since it´s in the same modell i want my single patch surf, i dont see how that can be used , and exporting and importing a iges to the same model sounds like a not preferable workaround , especially when you want to update your geometry.

//Tobias

Seems like offset 0 remains the same surface.

Workaround could be:  offset +1mm and the "offset approcimate" it back -1mm

well, actually No. You cant set zero as a value when offsetting a surf if you set the surfs to be aproximate (special handling). If you skip this, you can set it to Zero, but then it´s just a regular copy. The feature wont fail, but it will also NOT make an aprox surf , it will actually not make a surf at all.

And Yes , the workaround could be to offset it to a value, and then offset it back to the original position . The thing here is that when i do that in a complex surf , the result is too far off the original surf. ( Would be nice to be able to set a value for the deviation too, but first lets figure out how to create the aproximate surf!)

And hey, i just tried to get the result using copy or offset. If anyone have a different approach to create an aprox surf, I would be grateful to hear about it!

//Tobias

May i ask why you need the surface "approximate" or whitout tangential lines?

absolutly, when pattering instances over several patches , sometimes the pattern fail (cant create my instanses, but when pattering on an single patch surface, this wont happen) . Most often when it comes to an intersection where several paches meet!

//Tobias

I know paterning in surfacing can be a pain

I see no other way than what you tried now with the approcimate offset.

Ssome ideas that you could trie are. (if posible)

Trie to avoid the tangentional lines, use splines instead of  lines and arcs

Create reference patterns, instead of patterning the colmplete surface, pattern the features seperately using ref pattern.

Or if nothing helps create them seperatly and dont use pattern. then you can tweak the features to avoid the patch intersection.

Stefaan

Thanks for your suggestions!

Regarding tangentional lines - Yes, i use splines, or even rather i most often try to use higher degree curve (isdx curves) and use cv.s to manipulate the shape of the curves just to get the right lightreflection and form of my surfaces. The thing is that when creating complex shapes you have to create "more than one" surf , and you get intersections. (btw, by Tangentional lines, i suppose you mean patch intersections in the quilt) And yes, quilt intersersections can create the same issue.

//Tobias

Any more suggestions?

//Tobias

Tobias,

Will you be able to "replace" (Old School Patch) the offending surfaces with a new one? There is a technique that I use for this situation when the patterns fail.

Hi Dean!

Well, the thing is that "i need a new surface where i can place my pattern " , and yes replace ( i do remember old school patch 😉 ) could work just fine , but the thing is that the surf used for replacing has to be modelled and i want to skip that step!

I dont want to "model" a new surface for the pattern, i would like to use the surfaces already created (in some way...) and then get the same geometry (or very close to that..) but with (at least...) minimal patches or intersections on it.

It works pretty good using the offset command and special handling of all surfs when offsetting to a minimal value (like 0.1mm) and use that surf for placing the geometry to be patterned. If there is another way to create the "singlepatch surf" i would be great, then i can the perhaps even use the "replace" for the new surf, but thats a bonus..

( I bet creo can do this mathematically , like when you model something in freestyle , creo can convert this to a 4 sided surfaces geometry. I think there got to be a way to get creo to take my already created geometry and convert it to a similar geometry but placing new 4 sided surfaces in the best way to get a superb and smooth surface. Atleast maybe in the future )

//Tobias

Tobias,

I would say you will be modeling something "new" regardless of what technique you use. But I will ask the simple question first. Have you simply tried to pattern your features on their own first as surfaces and then Boolean them to solid? In this case it will not matter where surface boundaries on the solid are relative to your features. I do this with automotive grille patterns all the time for many of the same reasons you described in the thread.

P.S. I have found over the years that techniques like offset "0" and/or ".001" come back to bite you later. Especially so if you have surface copies and offsets as children down the model tree. I like to stay explicit with modeling.

Dean,

Yes you are right, i will model something new regardless of technique used. What i meant was that if i can add a feature, that is actually not a modelling feature it would be great. In short, i want to use the already created geometry and make something out of it, like "i want to use one of the pink icons and not a blue one". I do think we are talking about the same thing , and that we understand each other

Regarding patterning a surf first and then boolean it, that could work unless like in this case when the feature i want to pattern is a "offset expand" feature. (sorry for not giving you all the info regarding this model)  When making that feature, i get a geometry that i want to pattern using reference pattern and most of the times it works, but sometimes it fails. The failing of the pattern can most often be connected to when a instance gets close to an intersection or something like that.  If i copy the surfs made out of the expand feature, i cant make a ref pattern (logic) so thats not an option here as i see it? (thats another question) .

Thanks for your effort in trying to help!

//Tobias

Tobias,

You seem to be describing two issues. 1. is the geometry you want to pattern will not pattern in all situations and 2. the geometry you want the pattern to intersect has internal boundaries that prevent a result. I believe I am tracking you?

For No. 1:

a. Have you tried to use a UDF of the "copied" geometry and then patterning that?

b. Have you tried a Publish Geom or Inheritance feature for the geometry to be patterned?

For No. 2:

There is only one way I know of to get rid of the internal boundaries/rule lines of faces on the solid. You will have to create a uniform surface that duplicates the topography without the discrete faces. Then use a surface replace using that new surface. To keep it parametric to your model, do all the work within the model itself, not as a separate data set imported from another model.

Yes, now i´m describing 2 issues here. And i think that they are related in that way that if i can solve the single patch surface thing.

please take a look at the pic below:

IF... the green surface where made of, let say 5 different surfaces, (that are made by boundaryblends using curves and so on) , then it would have intersections between the quilts , and it would have patch lines (now i just made a quick style surf to show my actual problem) . Then i want to use "offset expand" to make the geometry i want to pattern, in this case "the stars" . (i could use use "offset- with draft feature" to get drafted sides on my stars, but i think those 2 works the same way techically speaking)  . As you can see, it works just fine in the pic below, but when "the green surf" is more complex, then sometimes the pattern just wont work. I do believe that if the green surf is as clean as possible, my chances to get the pattern to work will increase.

dean.JPG

So in that way , to answer your nr1 and 2 , i will begin with nr2:  "You will have to create a uniform surface that duplicates the topography without the discrete faces" . That´s exactly what i want to do, but i would like to achieve this not by modelling a new surf, i would like to know if there is a command that i´m not aware of, or a technique for doing this without actually create a new surf. The closest i got is to use "offset"-"special handling" and "approximate")

So, nr1: one solution that comes to mind after reading your post is that i perhaps could make the "stars" in a separate model, and then import it somehow using publish, and relate it to a c-sys thats patterned (could first create a datumpoint for the c-sys location and first pattern the point, and then the c-sys to ref to that, then perhaps the imported geo could be patterned in someway using reference pattern....or.., i dont know, could work...maybe. , but then i will get an unwanted connection to a separate model.

I could off course change the way of making the stars, and just model them using an extruded surface thats related to a point and then ref pattern it, and solidify... ? (here an udf would be nice)

//Tobias

Tobias,

Please give me your email address. I want to send you a model that I think solves your issue.

I am: -


I believe you can do this by copying the surfaces and using merge or possibly group.  However I would need to see the model and what you are trying to do in order to give you a definitive answer.

Ron

Hi ron,

Please elaborate your thoughts . The thing is that i want to get a single patch surf out of already created parametric surfaces. The surfaces thats alreday crated is made of several sweeps (old scholl "variable section sweep), some boundaryblends, and/or isdx surfs thats merged together in to one single quilt, but then i want to get rid of, or atleast cloce to, the patchlines. I cant see how grouping the features could help, but maybe i´m missing something!

//Tobias

just use aprox copy composite curve over the projected curves across the compound surfaces.  Hi Dean and Tobias!

Bart Brejcha

Design-engine.com

Hey Bart!

All good?

Well, i do know how to build high end surfaces using compositecurves, although i prefer higher degree isdx curves over that since i fell i get more controll over the shape. But, as you know, when creating complex geometry you need to build several surfaces, and what i´m looking for is a way to do the same thing as you describe for curves, but instead on surfaces. I.o.w, copy several surfaces and make them in to one single patch surf. it´s possbile using offset- special handling- aproximate, but not on zero value.

//Tobias

Tobias-

we are getting in Creo 4.0 the G3 functionality.  So exciting since we have higher order curves.  So excited!    I have a funny story for you concerning G3 and 7 degree curves w/ respect to Creo.  Ill email you. 

Bart Brejcha

Design-engine.com

-

Yeah i heard about the new stuff in 4.0 regarding surfacing, but i havent tried it...yet!! Looking forward to it though.  Please email me the story 😄

Keep in touch!

//Tobias

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