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I thought that may get your attention?!
Well SC isn't dead, but this currently free
Google Sketchup plug-in may very well bring this 3000 monster to a grinding halt. :cool:
(and may give Shark FX a run for its money too! :eek: )
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The Sketchup code base is built upon polygons which I believe provides some significant differences from ACIS or ParaSolids based modelers.
Tim Olson
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Ah Tim, that's interesting. What are the advantages and disadvantages of both approaches (apart from importing files from other ACIS/ PS based applications)?
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Scaling up a polygon equivalent of a curved surface reduces the surface definition, and consequent accuracy. We work from the curve or surface definition and concern ourselves with surface approximations afterwards, without losing underlying accuracy. With polygons, you get creeping innacuracies. It's near impossible to recover intended design dimensions if you export a curved object as .stl, for example, then reimport it and measure off the import. Sketchup's probably a threat to 3DS MAX, especially with some other plugins like Smustard's subdivision and smoothing, but trying to keep track of the transformations of lots of polygons often slows applications down a lot.
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Cheers for that Murray :)
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I wish I were more capable at maths, but how I understand things is like this: There's a vast number of definitions (infinite possibilities? Folks better than me at maths could say.) for any given curve, and trying to deal with all of them to isolate one would be a huge drag on a computer's speed and memory space. NURBS are a sub-set that limit the possibilies that a computer has to explore (or be programmed to!), while still giving us almost any shape we need, with some limitations and irritations. Just fifteen years ago, draftsmen were rated by how nice and clear their paper drawings were, and if you did use CAD, you had to take a file (sometimes covering several floppies) to a print bureau because office printers were dot matrix. If you asked them to explicitly define a compound curvature surface, you'd get a blank look and another kind of explicit instruction in response. The capability of today's NURB CAD was literally a fantasy back then.
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Originally Posted by: ttrw Cheers for that Murray :)
Dinosaurs.
There really isn't any economic argument for 2D drawings other than reference, or for legacy products. There probably are some industries that can continue quite nicely with 2D, but most manufacturers benefit from solids model derived processes, and NURB surfaces and curves are interpreted precisely (within a proscribed tolerance) by everyone in the supply chain.
If someone gives me a NURBS surface file, I can build them exactly what they want (within the limits of my machining capabilities) but I still need some information that drawings would provide. No interpretation necessary.
Give me the full solids model, with necessary details (threads/surface finishes/tolerances) and you can skip the drawings entirely.
There was a fellow that I helped some time ago build a little robot head to mount sensors (a 4th axis job with surfacing). He gave me some file from one of the online prototypers, and it was quite difficult for me to convert using CU (at the time) without my own interpretation. I told him to purchase ViaCAD and I could work with him again in the future.
He didn't or couldn't come up with the $100 bucks.
End of story.
tom
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Originally Posted by: tmay Dinosaurs.
LOL!
Yes but one thing you are forgetting, this is the United Kingdom, and today Thomas Wedgewood, the final bastion of the British industrial revolution, finally landed in the hands of the liquidators.
I wish we could load up juicy STL files 100% of the time, but all those ACAD old timers are still out there! ;)
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Originally Posted by: ttrw LOL!
Tom,
this is exactly the reason that I left the UK as soon as I graduated from college in the era of Thatcherism. That and there is not a lot of need for industrial designers when there is so little industry, and what there is is living in the early 20th century at best when steam ruled.
If I gave a client or vendor a 2d drawing instead of a solids file they would wonder about my abilities and tell me to come back with something they could use - like a solids file. The only reason for a 2d drawing is to spec tolerances, critical dimensions and finishes. Luckily I have not had to do one for years.
Shark FX 9 build 1143
OS X 9.5
3.6 GHz Core i7, 8GB, GTX 760 2GB
matter.cc
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It wasn't just Thatcherism that killed industry in the UK, British industry has been dying ever since sucessive governments after the second world war continued to prop up the Dying British empire. Thatcher was just the final nail in the coffin (not forgetting Blairism!)
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Originally Posted by: zumer Scaling up a polygon equivalent of a curved surface reduces the surface definition, and consequent accuracy. We work from the curve or surface definition and concern ourselves with surface approximations afterwards, without losing underlying accuracy. With polygons, you get creeping innacuracies. It's near impossible to recover intended design dimensions if you export a curved object as .stl, for example, then reimport it and measure off the import.
Well you know folks, I'm quite impressed with this model of the Guggenheim, done with Sketchup and made using a RP machine;
http://www.cadspan.com/
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Originally Posted by: ttrw Well you know folks, I'm quite impressed with this model of the Guggenheim, done with Sketchup and made using a RP machine;
http://www.cadspan.com/ Polygon modelers are useful for a lot of stuff, but I wouldn't want to build a die for a car body or a carbon fiber skin for a B-787 off of anything but NURBS, and I would probably spec a NURBS CNC control for the machining as well.
Why take a chance with anything critical.
I like the concept of RP, but I really like the concept of more affordable RP machines.
tom
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Originally Posted by: tmay I wouldn't want to build a die for a car body or a carbon fiber skin for a B-787 off of anything but NURBS
o_O
O_o
A B-787?!!
LOL!!
Who said anything about a plane?!
:D
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Originally Posted by: tmay
It's called 'cardboard and scissors'. I think it has a great future! ;)
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