SketchUp basics - precise editing of an object

I’m a rank beginner of SketchUp and would appreciate some very basic help.

I have followed several tutorials and can now draw houses with chimneys and porches, but can’t do the simplest things that are actually useful.

My ultimate objective is to model a 3D device that is basically a small reflector of light. For a reflector, it is perhaps moderately complex, with around 14 faces.

I’m sure an experienced SketchUp user could do the drawing in a few minutes, but I am a beginner, and I can’t do it at all. I can make rectangles and lines, I can rotate them and give them colors, and that is a lot of fun. But I can’t edit a line to place it somewhere precisely, edit it to change its length precisely, or orient it to an exact angle or slope.

I found an online tutorial on how to change the length of a line. I followed the instructions but it didn’t work. Nothing happened. So I erased everything and drew a new line. And then the instructions DID work. SketchUp mysteries! Anyway, the tutorial did not say how I can make the line a predetermined length.

So what I’m asking is how to do simple but actually useful tasks on SketchUp. For now I just want to make a line. Is there a simple answer? Or do I have to follow a course or read a book?

An edge of arbitrary length with at least one endpoint free can be changed to exact length in ‘Entity Info’.

If the edge is connected to other geometry on both sides you could draw an edge on top of it, running from one endpoint (A) towards the other endpoint (B) and clicking its new second endpoint (C) somewhere on the underlaying edge (A-B), Then immediately type its exact length and hit [Enter]
Now with nothing else selected but the ‘Move’ tool hover over the endpoint (B) to see the tooltip ‘Endpoint’. Press the Lmouse button to grab and move (B) to (C).

There are other methods that involve the use of say guides, construction lines and guidepoints.

Also you can move an edge’s endpoint along its own edge by first hovering over the edge till you see ‘On Edge’. Then press and hold down [Shift] to constrain movements to this edge. Now grab the endpoint to be moved. It can only be moved in the direction of its edge. … towards say an intersecting guide marking the desired exact length of the changing edge

I’ll answer in a different way, Wo3Dan was saying more how you would change something that already exists, to make it the length you want. I’ll say how you get the line to be correct in the first place.

If you take the Line tool and click/release at the location you want the line to begin, and then you move the cursor around, you’ll see the line’s length in the lower right of the window. You could mouse around carefully until the value is what you want, but another option is to type the length you want, and press Enter.

For example, if you wanted a five foot line you would:

  1. Click/release at the start location.
  2. Move the cursor in the direction you want it to go (hold down the shift key to constrain it to the major axes). Don’t click!
  3. Type 5’ (which will replace what was in the length field). Press Enter.

You now have a five foot line, and the line tool is still live. You could continue with the next line segment. It would be possible to draw something complex with only a single mouse click and a lot of typing.

To rotate something to a precise angle you would use the Rotate tool. You can click at one end of a line, click at the other end of the line, start to move in the intended direction, and then type the number of degrees, and Enter, to make the line rotate by that exact amount.

Thanks, colin and Wo3Dan. I appreciate the replies.

It’s interesting how otherwise competent people are reduced to morons when starting a new program.

I want to be able to draw the line (or other entity) exactly to begin with, but also to change the length and angle etc afterwards. I’m thinking SketchUp should be a design tool, and therefore it should be possible to change shapes and sizes frequently to test different possibilities.

So I’m a bit surprised at how difficult (relatively) it is to reconfigure an entity. I had hoped it would be easy as pie to stretch to an exact dimension, tip to an exact slope, center a shape, snap to other shapes, force symmetry across an axis, and so on. It looks like these things can be done, but might be tricky and require multiple steps.

I tried experimenting with edges as suggested by Wo3Dan. It works. But it looks like I have to position the end of the edge by eye when moving B to C. Or is there a way to have it snap into place?

Thanks again. I figure after a few examples like this, a pattern will emerge and figuring out further methods will be easier.

Sometimes you have to draw extra lines to help. For example, to move a square so that its center is at the Origin, isn’t easy. There’s no entity at the center of the square to infer what you’re trying to grab. But, if you draw a temporary diagonal line you can then use the midpoint of that line as the location to drag. Then it will easily snap to anything you drag it to.

“Inference” is the main thing for you to learn in SketchUp. With it you can do some actions that would be harder if you just had dimension info boxes to guide you. There are loads of YouTube videos about it, the first one that shows up looks promising: Using the Sketchup Inference System - YouTube

Lots of videos to watch. They are fun to watch, but trying to do something in SketchUp is not.

Now I’m trying to make a four-sided figure with sides that are 78, 69, 148, and 89 mm long. I’m finding that it is not possible. Every time I change the length of one, the prog changes one of the others. It is so much fun, but I am not getting anywhere.

This is a link to there concepts guide that will explain to you what you need to comprehend. Then take the time and follow the users guide for what you are tring to accomplish. If I can find them there a a bunch of specific videos that show the tools in action.

I wasted 4 to 6 months being side tract watch HOW OTHERS made it look easy and only got frustrated. Follow the basics with a split screen and dont worry about watching someone on You Tube design the Eiffel Tower in 12:00 minutes…

Is this what you are trying to attempt…??

ACH_.skp (21.1 KB)

It is possible. Here is one with the numbers you stated, only in inches. You need to understand what SketchUp is. It is a 3D modeling program. You “Build” faces and shapes. It is not a true 2d Cad program, but lines can be drawn.

Checkout and search for sketchup. There are over 60 videos tutorials and many that take you through the use of each tool

Simple exercise:
-1) draw two intersecting edges, any length.
-2) select the ‘Move’ tool
-3) hover over the center endpoint till you see ‘Endpoint’ popping up at the cursor
-4) left click and hold down to drag that endpoint to whereever you want. Even drop it on one of the other four endpoints, to “consume” one of the four edges. (SketchUps geometry is sticky)

Second exercise, almost as the first one:
-1) draw two intersecting edges, any length.
-2) select the ‘Move’ tool

-3a) hover over an edge till you see ‘On Edge’ popping up at the cursor
-3b) press and hold down [Shift] to constrain (movements) to that edge

-3c) hover over the center endpoint till you see ‘Endpoint’ popping up at the cursor
-4) left click and hold down to drag that endpoint along that constrained edge-direction. Even drop it on one of the other two endpoints, to “consume” one of the two collinear edges. (SketchUps geometry is sticky)

p.s. when applying a tool, see the tip on the left side down on the status bar. It will inform you when you can input value(s) to obtain exact dimensions.

added: Oops, you can only drop drag/drop an endpoint exactly on the other endpoint of the same edge when this second endpoint is fixed to/part of other geometry.

A bit like the Citicorp Center building in Manhattan.

The method I mentioned, of single click, move, type 78 Enter, move, type 69 Enter, move, type 148 Enter, click on the starting point, quickly gives you that four sided shape.

You didn’t say which video tutorials you’ve been watching.

I’d recommend you learn the basics by watching the official training videos.
Here’s the link … Trimble SketchUp Video Playlists

Aidan Chopra’s book, SketchUp for Dummies, and the accompanying videos are getting a bit old.
Nonetheless, they’re still among the very best resources for learning the basics of SketchUp.

Here’s the link … Aidan Chopra Video Playlists

This one pertains to your question.
Injecting Accuracy into Your Model

These are also great and THE BASICS, without them you will be frustrated…

Thanks, I appreciate the replies.

I don’t want to watch any more YouTube videos. They are all basically impossible to follow unless you already know what they are talking about.

About the four-sided figure that I was making - when the lengths of four sides are specified, and no more, then one can make an infinite number of these figures, because a fifth piece of info needs to be provided to specify the figure uniquely. I figured I could start with an arbitrary four-sided figure and then deform it until it looked like what I wanted. Imagine if I could lock the dimensions of the edges and lock the ends together, and then skew the figure as needed. That would have got me what I wanted. But I did not get that far.

Using the pencil tool and typing in the numbers does not work because it gets me four lines forming an open figure.

Ultimately what I wanted to do is make a bilaterally symmetrical box with edges having different but known lengths. And I tried that by making a rectangle, pulling it into a box, turning it into a component, copying it and flipping the copy, and mating the copy with the original. That gave me my symmetrical box, but with all the edges the wrong size. So I selected edges and moved them around trying to get the right sizes and angles. Two of those edges seemed to work, but the third balked and would not move where it was supposed to go. Then the other edges started to move on me. Erased everything and tried it over again a few times, without success in the end.

That’s when I thought I’d try the irregular 4-sided figure, with the objective of pulling it into a box, getting the right sized edges, and going from there.

The whole point for me to try this in SketchUp was because I ASSUMED it would be capable and allow me to easily modify 3-D objects and edges as required. I think my assumption was wrong.

I already have almost the whole thing drawn out (in 2-D) in PowerPoint. The problem in PowerPoint is that it is not friendly when you need to change dimensions while fine-tuning a design.

But SketchUp is also unfriendly, from what I have seen so far. Lots of hype, fun to work with if you see it as a game to make houses with porches and stairs. But it is a ■■■■■■■ if you think you can easily make 3D forms with precise shapes.

Another problem with SketchUp is that there is apparently no conventional manual. That means there’s no index, so it is not possible to look up specific things. Instead you have to search the Web for something like Edit Rectangle, and you get 1000 hits for MAKING rectangles and zero for editing them.

Therefore it starts to look like I have to read that Dummies book and view countless videos in the hopes of learning enough to do simple tasks.

In short, learning this program is going to take some serious study and practice and time.

I appreciate the advice and the links, I think you guys are knowledgeable and committed. I will have a look at them (except for the videos). But first, I’m going to forget about SketchUp for a few days and see how I feel about it then.

If you draw a four sided shape with fixed lengths, and you then want to distort it into other possible shapes, with the same four fixed lengths, you would presumably choose one corner to be anchored (otherwise the whole shape would just stay the same and move around). As you drag another corner, all four angles would be changing to make the shape still have the same fixed lengths.

As far as I know, SketchUp doesn’t normally allow that, but it does have the Ruby programming language you can use. It would be feasible for someone to write a custom plugin to do what you’re trying to do.

OK, this is not the time to do SketchUp programming!

I was just speculating about being able to deform the 4-sided figure. It would be handy, and would simulate physical reality for something like assembling 4 skewers of given lengths.

Another way would be to specify a diagonal or an angle, and have the program assume that (if it was able to do so). Yet another way would be to take the figure apart, put two edges together at a known angle, and snap the other edges to these two.

But I think once I stray from building houses with nice straight sides, the going will be tough.

One feature that wasn’t obvious to me initially was the ability to use the move tool to click on the end of a line and then just drag it somewhere else:

This allows you to easily move the end of a line around to any visual position. It also works for moving intersection points (vertices) the same way:

Selecting the endpoint and moving it produces the following:

Using the next highlighted point and moving it:

Then right-clicking on a line and selecting divide to create more vertices to click on:

Produces this:

Using the scale tool you can stretch it:

This process allows you to kind of iteratively get the shape you want. When you’re done, select the dimension you want to be the final one and stretch the tape measure across that by clicking on the starting point and then clicking on the end point. Then type the dimension you want it to be and you will be asked if you want to resize the model … click yes:

This scales everything so that the chosen dimension is the resulting size you need:

The dashed line that may be left can be selected and deleted.

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For those who might be interested, here is a drawing in PowerPoint of part of the device. This is the box with four different sides that I was trying to make in SketchUp. Of course the Ppt drawing is 2D. The top of the box is the middle part of the drawing. The solid lines are fold lines. To complete the box, there is a bottom part (not shown) that fits to the extreme left, lower left, lower right, and right edges.

The dimensions in the drawing are from a mockup that I made out of cardboard. The mockup took weeks to make, and is a bit lopsided. My goal was to straighten out the geometry, make a few improvements, and then make a better model out of cardboard.

I figured a 3D modelling program like SketchUp would be just the thing to fix the design. And it probably is, too. It’s just that it might take me weeks to figure out how to use it properly.

After having played with SketchUp a bit, I suspect it will take much less time to stick with Ppt, make a new interim model, fix problems by inspecting it, and then adjusting the Ppt drawings.

Paper.skp (78.3 KB)
I made a few assumptions from the sizes given, but I assume that since you mentioned “lop sided” that you would want a shape that was symmetrical down the middle; this makes it much easier to model (and technically you only need to model half of it, then mirror that half).

It’s easier to create the shape in 3D, then flatten each face out (rotate each face onto the same plane).

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