Sketchup is Inacurrate???

[Rich O Brien]

You dare judge Brother Jeff?

[Pilou]

These 1/4", 1/8", 1/16", 1/32" are for me perfect obscurantist measures from occultism !

[thomthom]

These 1/4", 1/8", 1/16", 1/32" are for me perfect obscurantist measures from occultism !

[TIG]

Off-Topic:
In the UK at least no one uses the arcane 'pounds, shillings and pence' any more!
The UK dragged itself into the 20th century when I was a lad...
12 pence = 1 shilling
20 shillings = 1 pound
There were even coins as ha'penny [½d] and farthing [¼d]
[somewhat illogically 'd'=pence ]
We had other coins worth 1d[penny],3d[joey],6d[tanner], 1s[bob],2s[2-bob/florin],2s/6d[half-crown] and banknotes for 10s[10-bob],£1[a quid],£5[a fiver]...
There were also olde coins for 5s [crown] and guinea [£1/1s]***
So something would be priced as "£1/10s/4½d"
Nows we have decimal pounds/pence and coins up to £2.
So it is now approx. £1.53.........

*** The 'guinea' was an interesting idea.
If you were doing a service like an auctioneer you priced/charged the buyer in guineas and paid the seller in pounds - thereby keeping the standard 5% commission [1s is 1/20=5% of £1].
Having a base-12 shilling [like the feet/inch system!] allows you to divide it up into 1/4,1/3,1/2,2/3,3/4 and 1/6ths [and with ½d you jumpp to base-24 so 1/8ths are possible - 1½d was 1/8th of a shilling; using ¼d even allowed 1/16ths !!], but not 1/10ths ! Of course we still use 12 hours, 60 minutes/seconds etc [and obscure 'degrees'] for that very reason...

I can still 'conjure' with the olde fractional feet-and-inches - but 'metric' IS so much easier...

[jgb]

when handing out a cultist..

Yeah, I saw that too. You posted faster than I could.

Handing out cultists.... what a concept.

[Jeff Hammond]

when handing out a cultist..

haha. good catch!

(I think i need a context checker on my computer as opposed to a spell checker )

[TIG]

At least you weren't handing out a cutlass [pirate theme...]

[Jeff Hammond]

.


ok, so here's a real world scenario showing why the offset tool w/ arcs is a no go… inferencing doesn't work because if i inference for the arc, everything else goes sour & viceversa..

wall_offset_error_.skp

wall_offset_error.jpg

…and that's a basic slice of a real world drawing.. this perimeter wall would actually be a lot bigger and possibly more complex in a full drawing.. the whole process has to be done manually where as if the offset tool worked properly, it'd be a big timesaver..

EDIT ugh.. that uploaded version of my skp didn't have any of my notes on there.. ?? i'll sort it out soon..

EDIT #2 -- ok.. fixed

[Jeff Hammond]

I can still 'conjure' with the olde fractional feet-and-inches - but 'metric' IS so much easier...

my daughter is learning length & volume in school right now..
her homework the past two weeks has been all metric stuff.. (you know.. how to move a decimal point around )

i just wish they were teaching her metric as 'the way things are' as opposed to 'here, you might see this stuff occasionally'.

[Rich O Brien]

That's a very good example Jeff

[TIG]

The USA is already quite 'metric'...

You have had 'decimal' money forever.
You buy coke/pop in 'liters'.
Your cars have 'cc' engine data.
The US Army measure horizontal distances in 'meters' [but then heights in 'feet' - as do aircraft the world over!].
Most complex science in conducted in 'metric'.
So I expect that much of the US space-program is 'metric' too...

Now if only we can get you into using a few 'metric lengths'...

I find it surprising that given the US's break with the UK just as the French were pushing their newfangled 'metric' system, that the US didn't adopt it too, much of the rest of the world did...
We are not trying to get you to adopt a decimal time or calendar system

[Pilou]

Remember the Mars Climat Orbiter
Some millions $ in smoking vapors for error between unities in translation!

[Jeff Hammond]

So I expect that much of the US space-program is 'metric' too...
:

right. much of it is. unfortunately, not all of it.
we crashed a probe into mars by accident due to some imperial/metric conflicts

re:length.
all of our official land surveys etc are metric as well.. it's just the tradesmen that won't switch. I think most of us would be into switching but most of our materials are still sold imperial only.

it's pretty much the govt and manufacturers of building materials that need to lead the way.


Edit. well, I see frenchy has beaten me to the mars thing

[Jeff Hammond]

That's a very good example Jeff

maybe one of these days I'll get the point across that I've been trying to

[Jeff Hammond]

I can see the argument from both sides for arc offsets because in the past I've wanted both results. Ideally SU will be given true arcs at some point. But from this thread I now understand why things are the way they are and on balance from an architectural perspective I prefer to have any offset from an arc create a consistent (wall) thickness which is what happens now rather than tapering the arc section to maintain a vertex offset.

I guess I'm now flogging a dead horse but the way it works now doesn't give a consistent wall thickness. see my last upload in this thread which shows an example using an actual wall.

[andybot]

Hey, what's better than a dead horse to beat! Anyhoo, wouldn't you use follow-me in a case such as the one you show? That way you are certain to have a consistent profile along the path.

[Jeff Hammond]

Hey, what's better than a dead horse to beat! Anyhoo, wouldn't you use follow-me in a case such as the one you show? That way you are certain to have a consistent profile along the path.

it would be nice if I could. but if I were to put a 2x6 profile at the end of one of those perimeter edges (in my latest example skp) then run follow me, it would produce the exact same (bad) geometry as offsetting the perimeter then push/pulling the face upwards.

these two tools (offset/followme)use the same brain..

[andybot]

oh. learn something new every day... I guess this one is a dead horse of the highest order. Oh well, back to ACAD.

Edit: oh hell, I'm back for more. The profile width is absolutely correct with follow me, but why is it not correct in your example? (5.489")

[Wo3Dan]

That's a very good example Jeff

maybe one of these days I'll get the point across that I've been trying to

Your first example, the one that you think is correct, doesn't have a constant wall thickness.
The other one (by your standards being incorrect) does indeed have a constant wall thickness.

I can see the occasional need for offsetting an arc to get predictable new arcs instead of curves with unpredictable radii. But here in your example the wall thickness is correct by using SketchUp's basic 'Offset' tool.

Why do you measure/dimension its thickness not perpendicular to its surface?

[Wo3Dan]

...Why do you measure/dimension its thickness not perpendicular to its surface?

Let me put it this way: you use 2x6 for the base plate. It's not a 2x6 anymore in your correct example. It is in the incorrect one at the right, (scene 4).
Due to the correct offset method SU correctly calculate the (inside) lengths, etc. that you marked in red. This is exactly what you'll get when you cut the 2x6 to match the outside frame perimeter.

[Jeff Hammond]

...Why do you measure/dimension its thickness not perpendicular to its surface?

Let me put it this way: you use 2x6 for the base plate. It's not a 2x6 anymore in your correct example. It is in the incorrect one at the right, (scene 4).
Due to the correct offset method SU correctly calculate the (inside) lengths, etc. that you marked in red. This is exactly what you'll get when you cut the 2x6 to match the outside frame perimeter.

it's an arc.. the only point(s) on the arc that are true are the vertices.. the straight segments in between have nothing to do with it..

draw an arc with 2 segments… there are exactly three points that are going to be true.. those are the endpoints and the one vertex in the middle.. those three point will be the only place to accurately measure the radius.. these are also the only points where you can measure the thickness of an arced wall.

for all intents and purposes, i could do the same drawing using only guide points to represent the geometry.. the lines connecting the guide points do not matter at all..

notice for this wall, i have original arc with segments spaced at 12" (arc length.. not segment length).. the reason for that is because i also want the studs to be on 12" centers and they must be placed on the vertices to be true.. the can't be placed on the straight segments because things won't line up..

[Pilou]

there are exactly three points that are going to be true

It's better than a broken watch who give the good true time twice a day!

[Jeff Hammond]

via_rhino.jpg

maybe this helps? (rhino)



.

[Roger]

Why does this matter? Is the project going to be build with a CNC machine or by a carpenter? The carpenter will read and cut to the correct dimension. A CNC machine the will facet the curve incorrectly. How many buildings are built with CNC machines. This is an honest quest as I don't know if it really matters. For a machine designer it would be critical if CNC is used in manufacturing. If the plans are meant to be read by a human and are annotated properly I don't see the problem.

[Jeff Hammond]

Why does this matter? Is the project going to be build with a CNC machine or by a carpenter? The carpenter will read and cut to the correct dimension. A CNC machine the will facet the curve incorrectly. How many buildings are built with CNC machines. This is an honest quest as I don't know if it really matters. For a machine designer it would be critical if CNC is used in manufacturing. If the plans are meant to be read by a human and are annotated properly I don't see the problem.

lol.. you're right.. the carpenter will read and cut the dimension given.. only it's the wrong freaking dimension

[Jeff Hammond]

oh. learn something new every day... I guess this one is a dead horse of the highest order. Oh well, back to ACAD.

Edit: oh hell, I'm back for more. The profile width is absolutely correct with follow me, but why is it not correct in your example? (5.489")

it's because you're measuring the arc wall at the wrong point.. i want to build a curved wall -- not one consisting of a bunch of straight 2x6s mitered together (in which case yes, the 5.5" width would be proper)..

but it's an arc -- and the only place an arc is accurate in sketchup is the vertices.. you have to measure your arcs/circles etc from there..

edit.. for instance.. draw a circle in sketchup then draw a few diameter lines across it… the only place where the lines will be the true length are at the vertices.. if you draw a line connecting a segment to a segment, it's going to be shorter than the actual diameter

[Rich O Brien]

Are you beating your head against a wall there?

[Pilou]

It's for that is not very cautious to build an atomic Plant from Su but no problem for draw it!

[Roger]

Why does this matter? Is the project going to be build with a CNC machine or by a carpenter? The carpenter will read and cut to the correct dimension. A CNC machine the will facet the curve incorrectly. How many buildings are built with CNC machines. This is an honest quest as I don't know if it really matters. For a machine designer it would be critical if CNC is used in manufacturing. If the plans are meant to be read by a human and are annotated properly I don't see the problem.

lol.. you're right.. the carpenter will read and cut the dimension given.. only it's the wrong freaking dimension

I would say the problem is with the architect who inserted his dimensioning at the wrong point on the drawing. In this case wouldn't you insert your dimension at the vertice where the measurement is correct? Or manually change the dimensioning if it MUST be inserted at another point? Not arguing, just filling gaps in my knowledge.

[Jeff Hammond]

I would say the problem is with the architect who inserted his dimensioning at the wrong point on the drawing. In this case wouldn't you insert your dimension at the vertice where the measurement is correct? Or manually change the dimensioning if it MUST be inserted at another point? Not arguing, just filling gaps in my knowledge.

the real solution is to draw it accurately in the first place. that way, the drawing is accurate and the dimensions are accurate... and any subsequent geometry in the model will be accurate and so will those dimensions.. and so on and so forth.
drawing sloppy then editing dimension is both hack and inefficient..

and again, you can draw this wall accurately in sketchup and obtain proper dimensions etc. it's just that you can't use certain tools (which should be the right ones for certain situations) to obtain the true dimensions.