Sketchup is Inacurrate???

pilou · 7 Apr 2012, 23:01

Thx
On a same plan
A funny thing : you can't offset one segment
You can Offset 2 segments not welded but touching them
You can't Offset 2 separated sets of 2 segments not merged but touching them

@Rich : not on this too old computer

jeff hammond · 7 Apr 2012, 23:17

@unknownuser said:

Thx

A funny thing : you can't offset one segment
You can Offset 2 segments not welded but touching them
You can't Offset 2 separated sets of 2 segments not merged but touching them

@Rich : not on this too old computer

right, but it makes total sense in sketchup.
it simply has no way of knowing which direction you want to offset if there's only a single line. with more than one line, you've defined a plane so sketchup now knows which direction to go.

pilou · 8 Apr 2012, 01:20

So maybe Radial lines or Radial Lines Fixed Length by Tig can help

here only Font faces were selected! (Snap is automatic ! )

select a CPoint + something then call the plug
Sand Box from scratch for draw lines extremities + some CleanUp/erase
And finally normal Offset for straight lines

Projections by Didier Bur or Thomthom Guides Tools for Put CPoints at some positions

And if you have exploded some arcs : Explode arcs centerpoint finder by Chris Fullmer

ely862me · 20 Apr 2012, 18:53

I'm working at the moment on some very small components and...yes sketchup is not accurate. When I draw some lines, sketchup grabs the lines from different lines,changes lengths,creates some other lines, hides lines.. as it's no able to work with small faces.

Beside that, orbiting or zooming in in small components it's a pain- the clipping/ disappearing objects issue makes i even harder .

DesertRaven · 15 Jan 2013, 00:28

[off:ywwrl90u]@jeff hammond EdIT -- the thread was bumped at this point.. conversation is now 9 months later than eli's post[/off:ywwrl90u]

The offset tool is not just a wee tad off, it is way off! And I see no reason why it should not be just fixed. Even if I use this as a conceptual tool only, there are underlying errors that one does not catch right away, only way down the road. I say the programming of the core of sketchup is just straight out sloppy and does, in many cases, not follow geometrical accuracy.
These issues should be honestly sought out, admitted and disclosed to anyone who considers using it to make a living.
By playing these errors down or ignoring them nobody is helped. What it boils down to is deception and who want's that? (the easy to use design tool, but some things don't count on)
Why is it so hard to admit these issues, which indisputably exist and try and work to fix them?
The units are precise enough just the execution of some commands lack performance; why? I just don't get the whole discussion there is no two ways! A command either performs geometrical correct or it does not. If it does not why not fix it?

sonder · 15 Jan 2013, 00:38

Huh? Never had issues with the offset tool. It's always been accurate for me, and I use it all the time.

Clipping occurs if you are far from the origin and set your field of view too wide.

TIG · 15 Jan 2013, 00:50

Some clear examples of Offset's inaccuracy please...
You shouldn't make sweeping statements about something like this without some backup

You type in a value or snap to something that is a known distance off, like a guideline...
It is that distance offset.
If you are later measuring offsets on 'arcs' remember that they are 'segmented' and you must measure 'square' to these lines, not from their vertices which will not provide the true offset as this is the 'miter diagonal'...
That is the only source of measurement confusion I can think of... but then that is mis-measurement... and not the application's inaccuracy ?

Which as far as I know is fine for most expected uses...
It's not for designing the innards of swiss-watches or whole city-suburbs but at normal 'building' dimensions it's just fine

DesertRaven · 15 Jan 2013, 01:00

@tig said:

:? Some clear examples of Offset's inaccuracy please...
You shouldn't make sweeping statements about something like this without some backup

You type in a value or snap to something that is a known distance off, like a guideline...
It is that distance offset.
If you are later measuring offsets on 'arcs' remember that they are 'segmented' and you must measure 'square' to these lines, not from their vertices which will not provide the true offset as this is the 'miter diagonal'...
That is the only source of measurement confusion I can think of... but then that is mis-measurement... and not the application's inaccuracy ?

Which as far as I know is fine for most expected uses...
It's not for designing the innards of swiss-watches or whole city-suburbs but at normal 'building' dimensions it's just fine

Well let us just pretend you never encountered what I'm talking about so here is an example:

jeff hammond · 15 Jan 2013, 01:11

@desertraven said:

These issues should be honestly sought out, admitted and disclosed to anyone who considers using it to make a living.
By playing these errors down or ignoring them nobody is helped. What it boils down to is deception and who want's that? (the easy to use design tool, but some things don't count on)

hey.. i tried back on pg 9

@unknownuser said:

oh, hey..can we get a sketchup rep in the thread ?

jeff hammond · 15 Jan 2013, 01:18

@unknownuser said:

Huh? Never had issues with the offset tool.

@tig said:

:? Some clear examples of Offset's inaccuracy please...

i'm seriously going to try to avoid getting into this again because last time around (this exact thread) i think i might of pissed off gerritt and that sucks.. he's one of my faves around these parts..

@TIG.. i've discussed this quite a few times with you (latest being in your smartoffset thread)
i seriously thought by now you recognized this error in sketchup but this post is saying otherwise..

this thread contains pretty much all i have to say on the issue.. maybe i'm not as clear as i could be (please let me blame my florida education for lack of communication skills ).. but please read through the thread / look at the .skps again.. maybe go into it with an open or fresh mindset just to humor me..

but Olav is absolutely correct.. the offset tool does not properly deal with arcs..

jeff hammond · 15 Jan 2013, 03:01

[preemptive]

and before rich calls me a gob o' shite again over this, i would like to say that i fully understand these are first world problems.. i'm just being nerdy about it but in the actual big picture.. i don't care.. at all

[no video.. audio only.... nsfw- language.. maybe a hundred fbombs..]

[/preemptive]

DesertRaven · 15 Jan 2013, 05:01

@unknownuser said:

@unknownuser said:

Huh? Never had issues with the offset tool.

@tig said:

:? Some clear examples of Offset's inaccuracy please...

i'm seriously going to try ...

but Olav is absolutely correct.. the offset tool does not properly deal with arcs..

Actually it is worse then only arcs, and to make it clear I am not posting this because I'm trying to bad mouth anyone or Sketchup as such, I am trying to bring some serious issues to light, that seem to just been brushed off with the lamest ever argumentation for too long.

@ TIG, I understand where you are coming from and I have seen much of your great work and effort to make this tool into something useful.
Please try and see my criticism out of the perspective of a every day user who usually never has the time to even go on this forum to discuss any issues they encounter in their every day work life.
I have looked at some of your plug ins and know that you do things different as it is done in sketchup using the native tools available. and I also know you and many others do a great effort to improve this software where it lacks functionality. You write plug ins to make it work or else if all was just good enough you would not even have a reason to do anything. Right?

So please Bear with me for the time being and I will provide more issues and examples where I see the need for improvements. And again I'm NOT asking for more plug ins scripts or more buttons to clutter up the interface.

I am also fed up with work- arounds where there hasn't been a fix for years.
I believe Sketchup can with it's simplicity stand up to any high priced CAD program out there if the core functionality was there. I have worked for years with Sketchup in a fast paced environment and have delivered my part accurate and to satisfaction for my customers. I have done so much research and I have been reading endless hours in this forum on how to work around issues that just occur.

I have lost many hours of my life working with sketchup, but have also saved many hours not working with other more complex software.
To me it is just crazy to see the potential and and for years only read lame excuses why nothing can ever get to the better; why known issues never get fixed. For years on end the only thing I hear is there is a work around... Oh it would not be sketchup any more ... and so on. The worst response I ever read here is "why would you want a cluttered up interface"

I actually think the Interface the simplicity is key to ketchup, I think many others have already learned and implemented simpler interfaces to their complex software. I would not complain about anything if the core of Sketchup would just work (accurate and satisfactory) if issues that are being brought up had been taken serious and fixed.

I'll post some more, to me, obvious fails of Sketchup in this thread and I'm sure a thorough job on the programming side can solve these unnecessary issues.

thomthom · 15 Jan 2013, 08:40

@unknownuser said:

and before rich calls me a gob o' shite again over this, i would like to say that i fully understand these are first world problems.. i'm just being nerdy about it but in the actual big picture.. i don't care.. at all

Do care about the small picture as well as the big. I get very annoyed when someone mentions from out of the blue a third world problem to mute an otherwise sensible discussion. Or non-sensible for that matter. As if we should never be allowed to talk about anything else.

Btw - Luis CK FTW!

Wo3Dan · 15 Jan 2013, 09:26

@unknownuser said:

..... i'm seriously going to try to avoid getting into this again because last time around (this exact thread) i think i might of pissed off gerritt and that sucks.. he's one of my faves around these parts..
.......

Jeff, nothing of the sort. You need to do much more than that. I highly value your view/opinion on this matter. And we discussed it for a while. At some points we may disagree. At others I think you were right for what you are working on. You needed some tool that offsets and end in a different way. How I wish that there were true circles in SU or at least true construction circles. The latter would not make SU much heavier. At some point I left the topic for what it was, I think when TIG came to rescue with a new plugin to help you out.
Peace, man!

TIG · 15 Jan 2013, 10:21

The native 'Offset' works just fine - within its own limitations.

My 'Smart_offset' removes reversed edges etc too but is otherwise the same creature...

'Offset' offsets Edges - that is all it does; it does not offset Arcs, except as if they were Edges.
This means that the two end-most segments of a bound set of segments [that you refer to as an 'Arc'] are offset quite logically by 'Offset', but that is just as if they were the equivalent selected Edges that had not been 'welded' into a bound-set to form that Arc.
So, 'Offset' ignores the bound-set's Arc-ness and always takes 'Edges'...
That's just the way it is.

If the native tool had been called more accurately 'Offset-Edges', then you shouldn't have been at all surprised when it didn't 'Offset-Arcs' !

There are regular gripes about SketchUp's lack of true Arcs and Circles - they are really special collections of bound Edges [forming the pseudo-Arc's segments].
I have made a several tools to compensate for some of these shortcoming - like TrueTangents and its siblings which allow you to find the 'real points' and not those from the intersections of lines and the Arcs' segments, which are always 'off'...

The very issue of Arcs offsetting as Edges prompted me to write this fix - ' Arc_offset_true' - earlier last year... http://sketchucation.com/forums/viewtopic.php?p=395769#p395769
Because only 326 members [out of 155,000!] have downloaded it the 'clamor' for properly fixing this issue 'formerly' is hardly overwhelming

If you use my tool in the appropriate circumstances you will get correct 'offsetting' of an Arc at its ends - as in CAD, where 'true' Arcs are available [in my fix it's actually just a 'Scaled' copy of the original Arc, with the scaling done about the Arc's center-point and calculated so the resultant Arc is suitably sized so it's the required distance from the original - bearing in mind that means when measured from vertex-to-vertex, and not segment center-to-center as with the conventional Edge-Offset]: this method contrasts with using the native 'Offset' tool which will always offset the Arc's segments as if they were just vanilla Edges...
It would be nice if SketchUp included some better Arc tools... but until then there are many adequate workarounds [mostly made by me] !

So... the real title of this series of posts ought to be 'Native Offset handles Arcs as if they were Edges, not as Arcs... Help!'

Alan Fraser · 15 Jan 2013, 15:28

TIG is perfectly correct (of course) The offset Tool works as an Offset Tool, not a Scale tool. In Olav's posted image above, you will find that the internal and external offsets are produced accurately; and the ends of those offsets are perfectly aligned with a perpendicular being drawn from the end points of the original arc.
Unfortunately, the consequence of the original arc not being a true curve, but a series of straight edges, results in these new end points not being aligned with the centre of the original arc.

Think of it this way; if the original arc had been a full semicircle, then the ends of the two offsets would be expected to be lined up with the ends of the original. In other words, all 3 arcs sharing the same baseline. However, because the curve is segmented, the only way this is going to happen is if the two end segments of the original arc are exactly parallel. You simply won't get this using the Arc Tool. You'd need to draw a full circle then rotate it so the the bisector ran through the mid point of two opposite and parallel edges....or use TIG's plugin.

It's effectively the same problem that is encountered when Follow Me is used along a curved path...the end faces may not be aligned exactly the way you would expect them to be on a true curve. It would be nice if both tools offered the plain vanilla and true-curve options.

thomthom · 15 Jan 2013, 16:15

@alan fraser said:

It's effectively the same problem that is encountered when Follow Me is used along a curved path...the end faces may not be aligned exactly the way you would expect them to be on a true curve. It would be nice if both tools offered the plain vanilla and true-curve options.

I'd argue that if it's a problem, which I happen to think of both these scenarios, it should be fixed. Make the computers do the work we want.

jeff hammond · 15 Jan 2013, 16:23

@tig said:

That's just the way it is.

and you're ok with that? why?

@unknownuser said:

If the native tool had been called more accurately 'Offset-Edges', then you shouldn't have been at all surprised when it didn't 'Offset-Arcs' !

wow..

@unknownuser said:

The very issue of Arcs offsetting as Edges prompted me to write this fix - ' Arc_offset_true' - earlier last year... http://sketchucation.com/forums/viewtopic.php?p=395769#p395769
Because only 326 members [out of 155,000!] have downloaded it the 'clamor' for properly fixing this issue 'formerly' is hardly overwhelming

maybe because it's not really fixing anything? i mean yes, you can select a single arc then use that ruby and offset it properly.. but what happens if you try to do something crazy-- like maybe another line is connected to the arc (i.e.-a very real world scenario)?? not much.. just the arc offsets and you still have to go in and manually draw things etc.. it just allows you to deal with sketchups shortcomings in a different order.. (normally, you have to offset the lines manually then fill in the proper arcs-- with the plugin, you offset the arcs first then go back and fill in the proper lines)

but that's beside the point.. the problem goes deeper than offsetting curves.. they are the easiest to fix manually but i use the offset tool as an example because it's the easiest to talk about since there's only a single curve involved..

to (try to) show the immensity of the problem, here's a drawing which shows how this same exact offset behavior causes the same exact problems in other tools.. and in geometry that is much slower to fix and/or draw manually..

every one of these examples is wrong.. (and if you're ok with saying "Well, that's just the way it is" then cool.. however, it doesn't change the fact that these are all wrong'

@unknownuser said:

but until then there are many adequate workarounds [mostly made by me] !

TIG man, i'm sorry but none of them work right and more to the point, they only affect a few situations.. if the problem was fixed internally (in sketchup itself), you wouldn't need to attempt to 'fix' anything plus all these other functions would work right too..

@unknownuser said:

So... the real title of this series of posts ought to be 'Native Offset handles Arcs as if they were Edges, not as Arcs... Help!'

no.. that shouldn't be the title.. again, i use arc/offset to illustrate the point in (what i feel should be) the simplest manner.. but when you start bringing more typical/complex geometry into play, that's when thing really start to go bad.. (or- if i offset an arc with su offset, i'm left with 10 or so vertices in the wrong place.. do the same thing with follow me and i'm left with 250 vertices in the wrong place.. use follow me on something other than a 90º bend and you're looking at potentially thousands of vertices in the wrong place)

jeff hammond · 15 Jan 2013, 16:41

@alan fraser said:

...
Unfortunately, the consequence of the original arc not being a true curve, but a series of straight edges, results in these new end points not being aligned with the centre of the original arc.

Think of it this way; if the original arc had been a full semicircle, then the ends of the two offsets would be expected to be lined up with the ends of the original. In other words, all 3 arcs sharing the same baseline. However, because the curve is segmented, the only way this is going to happen is if the two end segments of the original arc are exactly parallel. You simply won't get this using the Arc Tool.

i honestly don't understand this idea of defending sketchup as if everything ok.. it's not ok.. drop the guard.. especially by you power users that should immediately recognize these problems..

this is copy/pasted from a different thread.. would you be ok if any of these situations didn't work the way they did?

@unknownuser said:

what irks me is that the developers have done some things regarding the way arcs work in a polygon modeler which are correct.. for instance..

• if you use the arc tangent snap, (draw a straight line, choose the arc tool, click on one end of the line, find the light blue 'tangent at vertex' snap) then the first arc segment will not be inline with the straight line.. the first angle of the arc will be placed in the proper position.. it's accurate.. etc.

• entity info gives correct length of arc as opposed to sum of segment length (granted, this is just a little math calculation they're doing but still...)

• the arc's centerpoint is given accurately and it's not perpendicular to the end segments of the arc.. again, this is proper and accurate

• using the arc tool's half-circle snap... you don't end up with the end segments being parallel.. they're bent inward.. in other words, sketchup is calculating the position of the arc's vertices and not the segments-- as it should... but then you try to offset an arc and it moves the segments instead of the vertices ?tf

• when you're positioning an arc or circle (setting the bulge part of the arc), you're moving a vertex around.. not a segment

• the cardinal points are on a vertex, not a segment

so, they did do some things which are right and directly deal with the issues i have but why half-arse it ?? follow through please and tidy up the rest of it.. thank you

i mean really, you guys are talking as if it's ok to offset an arc using it's segments.. so if i'm hearing you correctly, all of those above situations are wrong..

when we draw a circle- should we be setting a segment into place instead of a vertex absolutely not.. and none of those situations should we be dealing with an arc's segments.. they work right.

so take your pick.. either an arc's vertices should be addressed when offsetting -or- an arc's segments should be calculated instead of it's vertices when drawing.. you can't pick 'well, they're both correct' because they arent'.. but you guys are insisting that 'su offsets arcs correctly'.. that's baloney and i just wish some people would look at this with a fresh state of mind.. with no ties to sketchup and no need to defend it.. i feel you'd then easily be able to spot the problem and start the process of getting this (long standing) issue in sketchup sorted out..

@unknownuser said:

You'd need to draw a full circle then rotate it so the the bisector ran through the mid point of two opposite and parallel edges....or use TIG's plugin.

ugh.. we've been through this in this thread already... doing that doesn't fix anything.. it just shifts the error to another location..

jeff hammond · 15 Jan 2013, 16:52

@wo3dan said:

Jeff, nothing of the sort.
Peace, man!

awesome.. thanks
peace!