Scale and units of the 3d objects
-
Here's the problem with AutoCAD: it's designed by and for American engineers, a group of people who refuse to adopt the Metric System but insist on working in tenths of feet.
Which tells you just about everything you need to know about translating measurements from SU to CAD.
-
@tpstigers said:
Here's the problem with AutoCAD: it's designed by and for American engineers, a group of people who refuse to adopt the Metric System but insist on working in tenths of feet.
Which tells you just about everything you need to know about translating measurements from SU to CAD.
They are not the only ones. Everything internally in SU is inches...
-
I perceive that the computer/Sketchup/OpenGL don't care if it's inches, parsecs, or Angstroms. Just give it a unit.
I perceive also, that computer modeling is really done proportionally, about the virtual bellybutton at 0,0,0 within a sphere whose outer limit is not specified.
So, on that basis, you could create a unit system, say of inches, or milimeters with a built in multiplier that overcomes the problem of those tiny empty faces. -
@mitcorb said:
I perceive that the computer/Sketchup/OpenGL don't care if it's inches, parsecs, or Angstroms. Just give it a unit.
I perceive also, that computer modeling is really done proportionally, about the virtual bellybutton at 0,0,0 within a sphere whose outer limit is not specified.
So, on that basis, you could create a unit system, say of inches, or milimeters with a built in multiplier that overcomes the problem of those tiny empty faces.No. SU has a built-in measurement system that uses real-world units, internally inches. AutoCad's units are inherently abstract - the program doesn't care a damn if for you "1" means an Angstrom or a lightyear. Both AutoCad and SU have problems with metric units that have been grafted on an interface that was originally designed for imperial users.
Anssi
-
@tig said:
When you export a 3d DXF/DWG file from Sketchup it should be in current units - e.g. mm.
If it's a 2d version I think it's always in inches.
If you give the file to a third-party then tell them what units to expect - they can adjust the scale on import/insert...
As has been said... recheck by importing the file back into a SKP and check its sizes..........No - the problem is the same for all SU DWG exports, whether 2D or 3D. 1 mm or m or cm is quite correctly translated into one drawing unit in the DWG file, but the unit indicators in the drawing file are written with imperial settings:
- the "Measurement" system variable is set to 0, while it should be 1 for metric.
- the "Insunits" system variable is set to 1, while it should be 4, 5 or 6 for mm, cm or m, respectively
I have been nagging about this for years. It's partly fixed for exports from LayOut.
Anssi
-
NO... This is correct the correct conversion a CDA file is always in 'units' and the user decides what these are... so if the file is in 'meters' then 1m becomes 1.000 DWG/DXF unit - i.e. the SKP exports as expected...
All that you have to do is tell the recipient of the CAD file what units it was exported in...
In the UK most people in construction use 'mm' but surveyors often use 'm'. So if you import a survey into your building plan you need to scale it x1000 !
It's no a failing of any system except that you must communicate with the recipients of you data about what units are involved in exchanged CAD files.With a SKP file it is much easier since it is always in inches and any user can swap to their preferred units in Model Info with little difficulty. In fact IF you add unit suffices to typed in dimensions you can work in each and every unit that you like - e.g. in a SKP if you are working set to display in mm and you type 12" you get a line 304.8mm long... and vice versa.
-
@thomthom said:
@tpstigers said:
Here's the problem with AutoCAD: it's designed by and for American engineers, a group of people who refuse to adopt the Metric System but insist on working in tenths of feet.
Which tells you just about everything you need to know about translating measurements from SU to CAD.
They are not the only ones. Everything internally in SU is inches...
Actually, I have no problems with inches. It's tenths of feet that drive me crazy.
-
When I was younger the UK's currency was 'pounds, shillings and pence' - 12 pence in a shilling and 20 shillings in a pound, pence were further divided into half-pennies and farthings. There were notes for 10/-, £1, £5 and £10.
The coins were 1/4d, 1/2d, 1d, 3d, 6d, 1s, 2s and half-a-crown [2/6] - not in common circulation there was also the 'crown' worth 5/-, the half-sovereign and sovereign [gold coins worth 10/- and £1], also there were memories of the defunct silver-three-penny bits guinea worth 21/- [introduced for agents to get their 5% - e.g. they sold your horse in guineas and paid you in pounds!] and the 'groat' worth 4d. To confuse things further there were 2/- coins labeled 'Florin - one tenth of a pound' - part of a failed attempt by Victorians to 'go decimal'. Doing sums etc at school was complex but you learn how to cope - you quickly learnt that there were 8 half-crowns in a pound but 10 2/- pieces and that 100s was £5 etc or that 100d was 8/4 or a third of a pound was 6/8d. Having base 12 for the shilling meant you could easily divide it into 1/4, 1/3, 1/2, 2/3 and 3/4...
Signs in shops would say £2/5/111/2 [spoken as 'Two pounds five and eleven pence hapenny'] - which you always rounded up in your head to £2/6/-.
In common parlance many coins had their own 'names'...
Jenny for a Farthing [it had a 'wren' on it and 'Jenny-Wren' etc] 1/4d
Hapenny [1/2d]
A Penny [or 'Coppers' in the plural]
Thrupence [or 'Joey' for the older silver 3d]
A Tanner 6d
Bob 1/-
Two-Bob or a Florin for 2/-
Half-a-crown or Half-a-dollar or Two-and-Six for 2/6
Ten-bob 10/-
A Quid £1
A Fiver £5
A Tenner £10
[more recently a Pony = £25]Don't get me started on old imperial units
I did my applied maths in imperial - horse-power, foot-poundals, BTus etc, my early physics in cm-gm metric [cm/gm/sec] and later in the European standard 'SI' metric [m/kg/s] and around the same time as the building industry changed from imperial to metric, so 1/8th scale became 1:100, and a 9" brick became 225mm etc - BUT even after all those years a builders-merchant will sell 2'6" door-leaves [mainly for domestic use because of the massive housing legacy] but architects on new developments - especially commercial work - will specify the parallel metric door-leaf of say 826mm [with a frame it's 900mm nominal] which are 'special order'... "Standard" timber windows still come in a range of sizes where some of them won't match the nearest hole left in a wall when you deduct a number of bricks! A piece of wood that was 2" [52mm] wide became the near 50mm as timber sizes were 'rationalized'... but in fact you'd struggle to get something that size unless you had it ripped from something bigger, as most timber is now 'regularized so it'd be ~47mm or planed it'd be ~44mm.....Decimal feet are as nothing!
-
No,No! The problem is Autodesk's monopolistic policy trying to force people to use only their products and file formats!
-
Man! I've never seen so many "No's" in one thread.
But thanks for correcting my perception.
Advertisement