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jdi000  
#1 Posted : Thursday, April 2, 2009 5:17:20 AM(UTC)
jdi000

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Tim


Any thoughts to having a option to join objects into a connected polyline versus current way converting to splines when using the join tool? Also a way to join all connected objects with one click rather than picking each curve one at a time something like how the chain select recoginizes connected curves. Maybe you hold down the option/ctrl and pick one curve and it connects all the curves that are connected. (AKA Trim Join tool in Autosketch.)

Ultimately if you could join connected objects into a polyline and be able to explode back to original curves as well as explode to lines!

I understand the join tool works to create a single continuous entites for some downstream features or needed if you are building surfaces off of curves, but the polyline would be useful in many other areas as well.


Anybody else have any thoughts?



Thanks

Jason
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blowlamp  
#2 Posted : Thursday, April 2, 2009 7:09:36 AM(UTC)
blowlamp

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Jason.
I agree 100%. This would save me several steps when I send a drawing to the CAM system, as it uses polylines to determine toolpath boundaries. It would be a VERY welcome addition for me.

Thanks, Martin.
Tim Olson  
#3 Posted : Thursday, April 2, 2009 12:08:50 PM(UTC)
Tim Olson

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>>to join objects into a connected polyline

Hi Jason,
Just to clarify, the resulting curve would be a polyline where all segments are lines? (IE splines would get converting into lines)

Tim
Tim Olson
IMSI Design/Encore
jdi000  
#4 Posted : Thursday, April 2, 2009 1:17:57 PM(UTC)
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Tim

A polyline where yes splines always get converted to lines, but could arcs and lines retain there properties if teh polyline was exploded. Kind of like you build polygons like for instance slot where its a polygon but you can explode to curves retaining the lines and arcs, or explode to all lines circel and straigh curves become approx lines based on reolution. Splines would always get approx as lines, but i don't know if you could keep the underlining spline and be able to explode back to splines?

Thanks

Jason
Windows 11, 10
unique  
#5 Posted : Thursday, April 2, 2009 1:51:57 PM(UTC)
unique

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Originally Posted by: Tim Olson Go to Quoted Post
>>to join objects into a connected polyline

Hi Jason,
Just to clarify, the resulting curve would be a polyline where all segments are lines? (IE splines would get converting into lines)

Tim


I agree 100% Jason that JOIN as a tool needs work!!

.......that doesn't make sense too me. What is its useful purpose?. I think if your happy with approximated, facetted, un-accurate geometry then maybe nurbs engine is not the tool to use :rolleyes:

A chain (series) of lines & arcs & splines when joined should retain their structure and become a polycurve not a polyline. A chain of lines would become a polyline.

Exploding any of the above should take the geometry back to square one....
Tim Olson  
#6 Posted : Monday, April 6, 2009 10:19:44 AM(UTC)
Tim Olson

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Martin, Jason

Just to clarify....Polylines are preferred to interface with 2D cam where these systems do not take well with splines? And these systems want a continuous line without duplicated positions at shared points?

Thanks,

Tim
Tim Olson
IMSI Design/Encore
jdi000  
#7 Posted : Monday, April 6, 2009 7:35:04 PM(UTC)
jdi000

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Hi, Tim

Splines are not treated well in some cam packages and yes some prefer only polylines that are joined as one continuous line.

A big advantage of joining a bunch of curves that make up a shape is to also check for non connected geometry since profile cutting like laser needs a connected toolpath so kerf values can be computed. Since alot of cam or laser / punch nesting software does not have cad features you are going back and forth from cad to cam cad to cam to correct unconnected geometry. Being able to join geometry before going to cam/nesting software ensures a seamless downstream interaction.

Example Workflow : Create sheetmetal parts or parts for cam join entire profile or toolpath as joined polyline export out to dxf then explode geometry back to arcs and lines (curves). The geometry will probably get modified on future rev so the curves lines arc are easier to modify than joined polyline.

3d modelers esp with sheetmetal unfolding leaves internal corners and edges of unfolded hems, internal cutouts on folded lines as unconnected splines may only be off by .001 or .002 but its unconnected geometry. All of these situations arise from how sheetmetalparts were modeled and whether someone takes the time to do radius or fillets on the unfolded walls vs on folded geometry. And the unfolding approximates with splines vs arc and lines.

Another example is bottles 3d modeled and then 2d drawings need made with dimensions but most software creates 2d profiles with splines which gets run through spline to polyline converters or other software. There are many software that convert splines to polylines but unfortunatly most don't do a real good job. And its slows workflow to have to open files in many different softwars just to get what you need.

See attached dxf files of a simple profile the first is v12 dxf the second is v2004 dxf. AutoCAD v12 dxf converted all splines to polylines, I don't think 12 could deal with splines. If you import the 2 dxf's into Shark see the difference v12 lots of lines grouped together and v2004 is a continuous polyline. So the dxf converters are handling these differently.

Thanks

Jason
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Tim Olson  
#8 Posted : Monday, April 6, 2009 9:58:09 PM(UTC)
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Thanks Jason, that really helped alot.

In another CAD system I did years ago we supported a composite curve. A composite curve is a single parametric continuous curve that references multiple curve types. A composite curve is G0 but not necessarily G1 or G2 and is associative to the original curves that defined it. If a composite curve were then exported as a polyline for R12, this might work for the workflow you described.

>>I don't think 12 could deal with splines.
Yes, right on. R13 was the first version of AutoCAD based on ACIS using precision NURBs. When you export to R12 with Shark/ViaCAD we automatically convert splines to polylines and NURB surfaces to 3D planar facets.


Tim
Tim Olson
IMSI Design/Encore
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