Slope/pitch dimensions

Continuing the discussion from SketchUp 2018 Wish List:

I’ve started this topic since the referenced discussion was drifting off the original wish-list into a specific FR or extension discussion.

Thanks, Steve. Could I have done that? I couldn’t see how, but perhaps because I’m not allowed to.

Can you move, or at least copy, the previous detailed off topic posts here too? So anyone coming fresh to this subject will have a good starting point.

For some reason they hid the Reply in a new thread option.
If you click the number of minutes/date etc in the top right corner of the post you get the option for a new topic.

As to moving things, that is still restricted to Team Members.

Thanks, @Box, it is indeed well hidden. Why on earth put it there? It doesn’t even look like a clickable link!

You should ask my Italian friend, Mr F Tifino!

I assume from his name, he doesn’t know either!

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@john_mcclenahan & @Box

I looked into this a while back when the “Reply as new topic” option stopped being more prominent. My search led me to I’m not going to take the time to search (again!), but somewhere in there lies the explanation for the move! This wasn’t a Trimble decision - they simply use Discourse hosting for this forum and leave the UI to Discourse.

I didn’t see anyone suggesting trimble was to blame.
Most people understand that forum changes of this nature come from discourse.
This is looking like a split thread that needs to be split twice more.


Could you do that, and move irrelevant posts out of this thread again? If not, maybe Steve could.

Fraid not as I mentioned earlier, only Sketchup Team members have split. move etc privileges.
And I’m waiting for them to even notice the tumbleweed I posted internally.

[details=You can also use the link button, and quote to your heart’s content …][quote=“Box, post:3, topic:46594”]
For some reason they hid the Reply in a new thread option.
If you click the number of minutes/date etc in the top right corner of the post you get the option for a new topic.

Actually it is easier to remember that the link popup panel is accessible via the chain link icon. (Ie :link: but leaning left.)

On it is the “Reply as linked topic” feature button (labeled “+ Topic”.)

Once the new topic edit form appears, you set the category (if need be,) and can then begin highlight quoting whatever you wish from the old topic thread.[/details]

Yeah, both options work, but are not obvious.

I don’t any discussion in this thread about Slope/Pitch so I decided to add my opinion.

The first option is my preference.

Thanks, Neil. How does one visually associate the slope dimension with the slope? Just proximity?

In the examples shown here there’s only one significant slope in the drawing.

And does the triangle or two line symbol actually match the slope?

What happens if the slope is greater than 45°? Does one put something like 17:12?

I don’t see a slope marked for W1 and W2.

Yes. Roof pitch is expressed as Rise : Run where the run (horizontal distance) is one foot.

I typically draw the actual slope over a 12" run.

I missed this new thread and posted an image here;

Yes, if the pitch is greater than 12/12 you would note and draw it as such: 14:12, 18:12, etc.

How far, in reality, does this go? What’s the steepest slope you would ever dimension in this way, rather than as an angle? And what physical object would it represent? I can mentally picture roofs up to maybe 60° but what else would use the x:12 notation for steeper slopes?


Usually Yes. In the example below the bottom of the triangle is actually drawn, but it is common for the bottom line of the triangle to be missing.

Yes[quote=“john_mcclenahan, post:14, topic:46594”]
I don’t see a slope marked for W1 and W2.

That is the interior webbing of the truss and the slope does not need to be known.

In the US pitch is given in inches of rise per 12" of run. So a 12 pitch is a 45 degree angle.

Mainly used in roofing. The steepest I ever remember seeing was on a steeple. The pitch was noted as 60/12.

Usually in text (as in a sentence) pitch would be noted as 4/12 rather than 4:12, but I’ve seen both.

I made a level marker by creating a Dynamic Component that calculates its z value into an attribute. Then I can place a leader in LayOut with an autotext referencing the attribute. The same technique might be used to create a roof pitch marker too.


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Sorry for slow reply - I’ve been busy on other things.

I have been doing a bit of homework on what ways are used to dimension slopes, in different contexts and different countries. Far from complete information yet, but initial suggestions for how a Slope Dimension plugin might display the slope.

1. North American Roofing dimensions:

This is where my trigger for suggesting such a Slope Dimension originated, and would probably be the first to implement.

Show as rise per 12" run, but not only in whole numbers.
Fractions can be used in some examples quoted in this topic thread, and by extension, other fractional values - e.g., ¼,⅜, ½,¾
In text show slope as 1/12, 3/12, etc, or ¼/12, in preference to 1:12, 3:12, or ¼:12.

Very steep slopes such as a church steeple can use a denominator much larger than 12 - for example, 60/12.

Use a triangle symbol with a clear background (not white), with or without hypotenuse, e.g.,
flipped horizontally if the slope goes the other way.

Either place text against the sides of the triangle symbol

Options 1a and 1b

or (simpler to program) add on the same level the slope as a ratio, separated by slash, as above.

Option2 (with or without hypotenuse: with is shown)

For visual clarity, the triangle symbol (or its two line replacement) should have its hypotenuse parallel to the slope being dimensioned, the rise vertical, and the run horizontal.

Options for this sort of dimensioning could include, in addition to those currently used in Angular Dimension 2, where relevant, whether to use Option 1 or Option 2 (text separately beside rise and run, or along the slope), and variant triangles type a or b (symbol with or without hypotenuse).

Angular dimension allows for specifying the size or directly picking the radius of a dimension arc.

The equivalent here would be what fraction of 12" to use to scale the dimension symbol and text, with a default of ‘full size’.

Two pick points on the slope could alternatively specify the length to use for the base of the dimension triangle, with the third pick point confirming the direction against which to measure the slope - usually, the horizontal x-y plane for a conventional roof slope. Or maybe one should always assume that ‘slope’ is relative to horizontal? In which case two picks would be enough.

2 European and metric countries roof pitch
I have limited information here. Perhaps a European architect on this forum could amplify the Wikipedia entry I found after searching for ‘roof pitch’.
“Countries which use metric measurement systems use a degree angle, or what fall there is per unit of run, and expressed as a ‘1 in x’ slope.”

3 Road, rail and civil engineering
In this use case, the angles involved are much smaller, and it seems that the convention is to specify the slope using 1 as the rise (numerator), with the run determining the angle. For example, 1 in 100, 1 in 50.

In this case, the triangle would often be visually indistinguishable from a straight line, and an Option 2 format with the text parallel to the dimensioned slope would be sufficient.

The separator would become the word in surrounded by spaces.

For this use case, it would be difficult to pick a horizontal direction.

4 General considerations

Perhaps the horizontal base should always be assumed both for engineering and for roofs? So only two picks would be needed, with the horizontal assumed.

Perhaps there could be a user selectable option to choose between the slash and a colon as the separator.

And maybe the program could either offer as options a choice of denominator or numerator as the fixed value (e.g., denominator of 12 for North America, or (say) 5, 10, 20, 50, 100 for metric dimensions; and numerator of 1 for small angles. Perahps also add ‘woodworking fraction’ denominators, as in SU Fractional or Architectural (Imperial) units - 1/2, 1/4, 1/8, 1/16th etc.

I’ve also seen a diagram while search for images of roof dimensionsng, with the roof pitch shown in plan view centrally on the roof plane(s). That would be tricky to implement. Perhaps the user could use a predominantly side view to generate the dimension group, then manually rotate it for a plan view?

What about the issue of rounding? If an angle is drawn in SU using the pitch method of input (3:12 for example), instead of an angle in degrees, a SU calculation of the angle will result in a value whose arctangent is an exact integer fraction.

Otherwise the value will be approximate, and (as an angle) preceded by a tilde (~) character. What should the plugin do for approximate values? If either the numerator or the denominator is a fixed value, that isn’t a problem - just use a tilde prefix when the result isn’t exact.

If however the program tries to ‘guess’ the nearest fractional representation with a maximum denominator, it gets quickly much more complex - perhaps I shouldn’t go there!

All I have time for tonight.

Any comments on these suggestions before I go further on trying to design a Slope Dimension tool?