(Twilight Zone) SketchUp vs fanciful sentient modeling engine

I have never used SketchUp. I had it installed for years, but it always seemed too difficult to master, so I never even tried. This time I plan on putting it to use at once on very simple projects, i.e. building a box, etc. Actually using it to build something simple should make a difference. Anyway, now that I’ve decided to use it, I want to start putting it to use immediately.

Is there a way to include scale? measurements? What I’m thinking about is to construct something on the screen, provide the measurements of one section and then have SketchUp provide the measurements of all sections of the construction. I have in mind saying that I want one section to be 72" long. Could SketchUp then tell me how long each of the other sections are? Going further, such a function would be able to tell me how many feet of 2X4s, plywood sheet dimensions, etc, I would need to actually build what I have constructed on the screen. These measurements should change as the image on the screen is changed. Is this being too ambitious?

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You draw in SketchUp at full size. That is, if you want a 2x4 that is 72" long, you draw it that long. There is a dimension tool in SketchUp so you can add dimensions to your model. If you draw it correctly, you can generate a cutlist with any of several different cutlist extensions. You can get sheet materials listed separately from lumber and so on.

I use SketchUp to draw furniture and I create plans for building much of the furniture I draw. There’s no problem with getting accurate and precise output but it is a computer program. The quality of the output is only as good as what you put into it.

Hmmm, well, that’s a start. If I understand you correctly, you have to supply all of the dimensions. SketchUp won’t calculate any of them. Is that right?

SketchUp can’t read minds. You have to draw what you want but there are shortcuts. I generally draw things that define the outside of project and then draw the rest of the parts to fit in between. On a table, for example, I would draw and place the legs where they need to be and then use them as references to draw the aprons and the top.

Once the model is complete, you can add dimensions with the dimension tool. It’ll display the distances between the points in the model.

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In addition, once you have made some parts to size and placed them in the model, you can usually use SketchUp’s inference system to cause additional ones to snap to the correct size, either matching existing ones or fitting between them.

I guess the only way for me to clearly understand is to start using the program AFTER reviewing all of the video tutorials I can find. Just to make sure that I am being understood, let’s start with the classic right triangle with sides of 3, 4, and 5. The SketchUp I would like would change the dimensions of the third side to reflect the change you make in two sides. It would be sort of a graphic trigonometric functions table except that the lengths of the sides rather than their angles would be shown.

There are ways to do that.

Okay, I just thought of a better way to express it. You give the measurement for one line in your construction (call it the base line), and SketchUp gives the measurements for all other lines in the construction. How about that? Can SketchUp do that? Can any 3D modeling program do that? No more questions from me. I promise.


No. SketchUp won’t do that. It sounds to me as if you should really hire someone to do the drawing work for you.

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This is commonly referred to as clairvoyance. Computers are just tools.

No and No. Not, in the “intelligent” way you are describing.

But SketchUp can have a component, drawn in your proportions, and you can then use the scale tool to uniformly scale the component, keeping the proportions.

It does not matter what your desires are. SketchUp is what it is, and how it is, because it was designed to work the way it does.

You will have much less frustration, and learn quicker, if you just accept SketchUp the way it is (for now.)

Watch the online tutorials and read the online User Guide.

The best way I think, would be to watch one tutorial, then read the user guide section(s) that applies to what that tutorial covered, then re-watch the tutorial. Lastly repeat what the tutorial taught in SketchUp.

Feel free to post as many questions as needed, but start a new thread for separate questions so that they may be marked as “solved”.

(Moved to the main SketchUp category, and attached a few tags.)

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Here is an example of a model, that has two instances of a component named “triangle 3-4-5”.

The second instance has been scaled uniformly. Since the dimension objects are also inside the component definition, they get scaled as well, and update automatically whenever you stop stretching with the ScaleTool.

triangle_3-4-5_demo.skp (37.2 KB)

Of course I had to draw all the component’s entities and dimension it first, then select everything and right-click and choose “Make Component”.

Then I inserted a second instance beside the first, and scaled it.

BTW, the triangles are facing down because they were drawn on the XY “ground” plane. I left them this way because I though they’d stand out better in the screen shot. But then used a print style instead.

My thought is that it’s long past time for a 3D modeling program to be able to do that. Frankly, I m surprised that it is not yet possible. Maybe tomorrow. By the way, the drawing part is not the problem, it’s the measuring part, something that you would think a computer could easily do. Anyway, thanks for an answer that cannot be misinterpreted.

Thanks for that. I have been doing a little searching, and I’ve found a few very useful and interesting sites. I haven’t found exactly what I’m looking for, but I did find one that can find the third side of a SCALENE triangle if you supply two sides. That’s closer to what I would like to see. In fact, I believe that there has to be something like what I have been looking for. Here’s the way I see it: (1) you draw a line of known length (2) the computer counts the pixels for that line of known length, which can be called the “basis line,” or “reference bar.”(3) you highlight another line (4) the computer uses the information from the “reference line” to determine the length of the second line, etc. That’s one way, and I can think of many variations, but that’s enough to give idea of how it could be done. Doesn’t that sound reasonable?

No it’s not. You draw a line. You say that it is 6”. The computer examines it and finds that it is 298 pixels long (298 pixels for 6"). Then you highlight another line. The computer measures it and determines that it is 823 pixels long. Then, using the law of proportions, you get the following: 298/6= 833/x. 298X=833x6, 298x=4998, X=16.77”. I find it hard to believe that the computer can’t do something that I can do.

But if the line is in 3D space, the number of pixels it occupies isn’t only a function of its length. It depends on the angle of view, and how far away the viewpoint is from the line.

Have you tried searching for ‘parametric design’, which seems to me to be more possible than your ‘magic’ computer that just ‘knows’ what you intend?


That’s an excellent point, one that I had not considered. Even so, I’ve been looking into the possibilities. I’ve already purchased one pixel counter, and I have asked for more information on three others. This is the way that progress is made. It’s one thing to say, “No! no! a thousand times no”!and another to keep an open mind. I’m looking around and learning. You have raised a very important point, though. I can’t deny that. I’ll have to ponder it; however, nothing comes to mind at this point. Having the computer adjust for those and other variables is theoretically possible, but not for a desktop project like this.

Aha! I just thought of something. It is possible to draw in an object in 3D without using perspective. I can’t remember what it’s called or the details, but maybe that’s the answer. I’ll certainly be looking. Thanks for mentioning this, though. The fewer surprises the better.

Failing that, and as a poor second, you can make use of one diagram per plane. In other words, a cube has six sides but only three pairs of sides. So, and it wouldn’t be ideal, you could work with only three diagrams. That’s for a cube, but most objects are not cubes. Fortunately, I’m now thinking of cubes and rectangular prisms.

Frankly, you are over-thinking things. Why don’t you first learn how SketchUp works instead of spending all your time dreaming up ways it could work but doesn’t.

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Well, it’s a good exercise; besides, I’ve now settled down, but only after examining the various possibilities. That’s it for me.