Using fractions for input in the scale tool

Hello

I would have thought that, because the scale tool scales objects it should be able to accept fractional input, rather than just integers or decimals. If I want to uniform-scale an object down to two thirds its current size I would like to input 2/3 rather than 0.6666…

I have looked for answers, but have been incapable of finding any, and I refuse to believe I cannot use fractions for uniform-scaling.

Am I doing something wrong?

The scale tool accepts input in relative scale and absolute dimensions. You can type 3 to make the object 3x as long as it currently is. Or type 3’ to make it exactly 3’ long. Type .5 to make it half as long or .5m to make it exactly half a meter. Between these two one can generally achieve any transformation needed.

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Thank you for the prompt comment. I do know and understand all the above-said, and don’t mean to sound rude with my reply.

I feel the point of my question is missed as the example given is using a very convenient half (0.5) for scaling, following with “one can generally achieve any transformation needed.”

What should I do, then, to uniformly scale down a 1m long object to one third of its length? If I type 0.3 am I generally achieving the transformation needed? I am left wondering if I could have used 1/3 instead - because it does not make any sense that I cannot. If I have to use something equivalent to the 0.5 given in the example, do I use 0.3, 0.33, 0.333, or…? - this is my question.

Incidentally, a work-around for the above would be to use the divide tool on a 1m line at the handle that is being used for the uniform scaling, and move the handle along the first third…

Cheers,
Jorge.

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I get the request. I can see how it might be useful.

I suppose this would be SketchUps question too. Since 1/3 of a meter is an infinite decimal it is not actually a point in space, so where should SketchUp round to? And if you know how many decimals of precision you need, why not type it?

I’m not dismissing the request, I just find in modeling actual objects this never comes up for me. Everything has to have a real number that someone can measure to build with and 1/3 of a meter isn’t on the tape measure.

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I’m glad we sort of agree :slightly_smiling_face:

A hypothetical example: 1 km subdivision has to be reduced by one third (for whatever odd reason.) Survey requirements ask to the nearest centimetre. The scale factor used would have to be 0.66666. I would rather type 2/3 and let Sketchup figure which length or coordinate points it is keeping in memory to minimize error as the model increases in complexity. Even a job requiring a precision to 1/16 requires 0.00001 if working in inches.

Not everything built in Sketchup is something that is measured/can be measured with a tape measure, where 1/16 or 1/32 precision is usually “good enough” (unless you are laying out a set of timberframe stairs with 16 risers, and a 1/32 error per riser can be equivalent to being up to 1/2" off in bottom-nosing-to-top-nosing length of the stringer) I believe, this is one of the reasons we have tolerances, because of rounding errors due to recurring decimals and irrational numbers…

Cheers.

I suppose it is slightly odd that you can type a fraction into the measurements box when, say drawing a line but you can’t do it for other things like this.

I haven’t tried it but is this a workaround: put a construction line on the static side of what you want to stretch. Copy it to the opposite side and enter /3 to create third divisions. Then use those intermediate construction lines to stretch to. Bit long-winded admittedly.

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I usually scale to 0,33333333333333333333333 or the like. SketchUp has a finite precision internally so if you just hold down the key for a bit you get the same result as an actual division. However, it would be nice if SketchUp supported 1/3 or 2/3 as inputs, but it may clash with imperial fractional inputs.

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2/3 is taken to be a request to make it be that size. If you try resizing a square it comes out with a diagonal of 2/3 units.

Yep, that is what I suggessted above. I usually do this when designing stair stringers. It never works if you just copy and paste the first rise/run convo…it always ends up creeping up…

By using a line with divisions we just let sketchup do the work to figure out that 1/64"

Agreed. However 1/3 is dimensionless and 1/3" is dimensional. I’m think that, if possible, that would be a good way to differentiate as inputs.

Hi, yes, I saw that. See my reply to eneroth3. Just as we can use 1, 1’, 1m to differentiate between units in the dimension box, would it be possible to implement 1/3, 1/3", 1/3’, 1/3m?

I do understand when you add a dimensionlees njmber it defaults to your default units, but it seems this would not be an unsurmountable obstacle.

How about 1/3p (for proportion) just like we have 3:12 for pitch, or 3h5m34s for degrees, etc…?

@DaveR, why withdraw your post? I was almost at the end reading it and was thinking of “Liking” it.
Phuf… gone. Why?

After posting it, I figured the OP wasn’t interested in a solution they could use now to do what they asked for. I think they really intend this as a feature request.

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Still, your solution is worth mentioning here for others. Just like the OP’s own solution to use the ‘Divide’ option on an edge and use the new endpoint as reference.
A feature request is quite valid, yes.

Hi, I used the “divide” solution, as I do often times. I had just never come across having to use it for scaling.

My intention was to find out if I was doing something wrong not being able to use proportional scailing…You are right it ended up being more like some musings and some sort of feature request… :thinking:

True. Usually SketchUp interprets numbers as lengths based on the Model Unit settings, but for Scale tool dimensionless values are already supported, so there shouldn’t be a clash.

Just be aware that if you try to use Imperial/US Customary units in the measurement box in a drawing set to metric units, you get very confused results even in the latest version of SU, especially with fractional inches.

See SU doesn't recognise fractional inches (e.g., 1/2") as an imperial measurement when units are mm

There are several past Feature Requests asking for the measurement box to accept arithmetic expressions. In general, it doesn’t. There are a few exceptions, which I can’t remember at the moment.

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A problem with that idea is that in all other cases you can leave off the units part. 6 in an inches document is the same as 6", and 10 in a metres document is the same as 10m. How would SketchUp know if you were leaving off the units or trying to do a scale fraction?

Perhaps one way would be /3. That is, you start to scale, type /3, and that would mean that you want the scale to be one third.

But say I wanted to scale the (any) selection to 2/3 in one go.
There must be a better composition than /3
I know, the following step could be to scale up with factor 2.

Until then I would isolate a selection together with a “dipstick” in a group. The dipstick would be a specific length to begin with. Say for scaling with factor 5/7… the length of the “dipstick” would be 7 units. Then the ‘Tape Measure’ tool would allow you to perfectly resize the group’s content to 5/7 the original size by measuring the “dipstick’s” length > type 5 units > anwer SketchUp’s question with “Yes” and [Enter].
I prefere to let SketchUp do the work.

There must be a well thought of intuitive combination of characters to allow as input straight into the ‘Measurements’ box to extend the use of the ‘Scale’ tool for simple fractions, as requested by the OP. A nice feature request.

How about x2/3?