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ACIS / TC Surface......"Reversible!"
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December 11, 2012, 11:41:00 PM
This must have been requested scores of times.
Now we are so many versions into Turbocad and have 16bit at our disposal, we STILL get this limitation! It would be nice to at last see an end to this major limitation:

Warning message:

"Note that when an ACIS Solid is transformed into TC Surface or Smesh, the transformation is not reversible, you will not be able to get the original ACIS Solid if you transform the TC Surface back into an ACIS Solid."

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Alan.
Platinum 21. & Deluxe 21.
TC user since 1995. (version 3)


* December 12, 2012, 11:23:38 AM
#1
Agreed.

Henry H

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December 12, 2012, 12:14:23 PM
#2
16 bits.....or even 64 bit, hi Henry, you knew what I meant, thanks!

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Alan.
Platinum 21. & Deluxe 21.
TC user since 1995. (version 3)


* January 12, 2013, 04:48:56 PM
#3
Are we talking reversibility or mesh-to-nurbs conversion?   Autodesk bought T-splines because it can convert facet models into nurb models - but it can only do that by converting every individual facet into an individual nurb surface that's tangency-continuous with its neighbours.  It doesn't recognise features like filleted edges, contiguous surfaces, cylindrical surfaces composed of multiple faces, or even contiguous planes.  Surfaces and smeshes can selfintersect, which ACIS ordinarily forbids because the intersection volume is usually undefined, which means the kernel can't derive physical properties like density or CoG.  Addressing RAM is a fairly minor consideration.   There's a premium software suite called INUS Rapidform that's just been acquired by 3DSystems that's been converting meshes to nurbs-with-features for years, in Windows 32-bit.  It's very expensive, and it's a long way from automatic.  Users have to identify features and evaluate the order-of-creation, then Rapidform can do a best-fit-within-tolerances for what's left. 
Keeping your original solid, with part tree, and converting a copy into a surface gives you 100% reversibilty....
« Last Edit: January 12, 2013, 05:28:35 PM by murray dickinson »

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January 13, 2013, 12:48:25 AM
#4
Are we talking reversibility or mesh-to-nurbs conversion?   Autodesk bought T-splines because it can convert facet models into nurb models - but it can only do that by converting every individual facet into an individual nurb surface that's tangency-continuous with its neighbours.  It doesn't recognise features like filleted edges, contiguous surfaces, cylindrical surfaces composed of multiple faces, or even contiguous planes.  Surfaces and smeshes can selfintersect, which ACIS ordinarily forbids because the intersection volume is usually undefined, which means the kernel can't derive physical properties like density or CoG.  Addressing RAM is a fairly minor consideration.   There's a premium software suite called INUS Rapidform that's just been acquired by 3DSystems that's been converting meshes to nurbs-with-features for years, in Windows 32-bit.  It's very expensive, and it's a long way from automatic.  Users have to identify features and evaluate the order-of-creation, then Rapidform can do a best-fit-within-tolerances for what's left. 
Keeping your original solid, with part tree, and converting a copy into a surface gives you 100% reversibilty....
Not really Murray, simply for it not to be excluded from the undo last actions list.

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Alan.
Platinum 21. & Deluxe 21.
TC user since 1995. (version 3)