You are doing everything correctly. But there's obviously something odd going on. Firstly we should know what version of Inkscape you are using. You can find this by looking at Help > About.
The second question is about the Union. It can sometimes change the shape's opacity, does the shape disappear as in a deletion or does it disappear in terms of opacity?
As Martin said, it sounds like you're doing everything right. I will note that you don't need to do Path > Object to Path first (Inkscape will implicitly convert most objects when performing Boolean operations), so you could try skipping that step to see if it makes a difference. But it should work either way.
After the object disappears, try switching the display mode: View > Display Mode > Outline. That will show an outline for all objects, regardless of their opacity or style. If you still can't see it, try uploading a version of the file just before the Union, and another just after, so we can look at the structure of the content and see if there's anything odd going on.
In outline mode you can select the object, but changes to opacity won't be visible there. With it selected, switch the view mode back to normal.
There are various ways in which it could be made transparent, but the main two are that the object itself is transparent, or that it has a transparent fill. Both of these can be fixed from the left end of the status bar, at the bottom of the Inkscape window. You'll find some controls that look something like this:
In this case the fill is completely transparent (as indicated by the chequerboard pattern on one half of the "Fill" colour swatch), and the object itself is also completely transparent (the zero in the opacity spinbox, labelled with "O:").
If your problem is due to either of these, a right-click on the relevant control will help. For the fill colour, right-click on the swatch and choose "Make fill opaque". For the opacity, right-click on the spinbox and select 100%.
If neither of these is the cause of your issue, upload the file as there are myriad ways in which an object can be rendered invisible in Inkscape and we'll be able to narrow down which it is a lot faster.
I just started over in a fresh document and everything is working exactly as expected. Dunno what's mucked up in the file I was working in, but I'm moving on until I break stuff again.
I'm curious what happened, if anyone sorts it easily, but don't burn cycles solving a problem nobody has.
The content of the file is clipped. If you go into outline mode you can see the green clipping path, and the black outline of the shape. When you apply a clip, only the areas inside the clipping path remain visible. In this case the clipping path is completely separate from the shape, so clipping has the effect of hiding the shape entirely.
Pay a lot of attention to the status bar in Inkscape. In this case, selecting the black shape in outline mode shows "Path 10 node; clipped..." which was enough to immediately indicate the problem to me.
I thought that the mention of "clipped" in the status bar might jog your memory, as presumably you'd applied the clipping path in the first place. But if it was as a result of just clicking round and experimenting, I can understand that it may not have registered consciously.
With regard to the clipping in your file, select the black item in outline mode and right-click, then choose "Release clip" from the context menu. Voila, your objects are visible once more.
You might find some of my tutorials in Full Circle Magazine useful. The magazine is a free download. There's an index of articles here: http://www.peppertop.com/blog/?p=1563
Yes, I was clicking around doing all kinds of things without paying enough attention. Years of experience with AutoCAD and Photoshop gave me a false confidence about Inkscape. I've dialed that setting back a wee bit, and I'll be rummaging through all the articles (h'ray!) and enjoying a couple rants about The Cure and Blur (with which I concur entirely!)
Beginners' Questions combine two objects (union and combine both fail)
Inkscape.org
Long time Photoshop user, new to Inkscape (I understand the basics of vector vs. bitmap.)
Got as far as two shapes, a semicircle and an arc. Cannot figure out how to make them into a single shape.
Select both, choose Combine or Union:
Combine deletes the arc no matter which I select first. Union makes them both disappear.
Selected each, Path | Object to Path:
Now Combine does nothing, Union still makes them both disappear.
Assuming I'm making some rookie mistake.
Hi Joel, Welcome to the forum.
You are doing everything correctly. But there's obviously something odd going on. Firstly we should know what version of Inkscape you are using. You can find this by looking at Help > About.
The second question is about the Union. It can sometimes change the shape's opacity, does the shape disappear as in a deletion or does it disappear in terms of opacity?
As Martin said, it sounds like you're doing everything right. I will note that you don't need to do Path > Object to Path first (Inkscape will implicitly convert most objects when performing Boolean operations), so you could try skipping that step to see if it makes a difference. But it should work either way.
After the object disappears, try switching the display mode: View > Display Mode > Outline. That will show an outline for all objects, regardless of their opacity or style. If you still can't see it, try uploading a version of the file just before the Union, and another just after, so we can look at the structure of the content and see if there's anything odd going on.
Sorry I forgot to include that necessary info. It's v 1.0beta1 (32d4812, 2019-09-19) on a Mac running Catalina.
It appears that it is indeed changing the opacity. Outline shows the object. (Extremely helpful suggestions from both of you; thank you.)
Now I can't sort changing the opacity . . .
In outline mode you can select the object, but changes to opacity won't be visible there. With it selected, switch the view mode back to normal.
There are various ways in which it could be made transparent, but the main two are that the object itself is transparent, or that it has a transparent fill. Both of these can be fixed from the left end of the status bar, at the bottom of the Inkscape window. You'll find some controls that look something like this:
In this case the fill is completely transparent (as indicated by the chequerboard pattern on one half of the "Fill" colour swatch), and the object itself is also completely transparent (the zero in the opacity spinbox, labelled with "O:").
If your problem is due to either of these, a right-click on the relevant control will help. For the fill colour, right-click on the swatch and choose "Make fill opaque". For the opacity, right-click on the spinbox and select 100%.
If neither of these is the cause of your issue, upload the file as there are myriad ways in which an object can be rendered invisible in Inkscape and we'll be able to narrow down which it is a lot faster.
Excellent detail. Fill and opacity were both already as they should be. Here's the file. Thanks again for the help.
I just started over in a fresh document and everything is working exactly as expected. Dunno what's mucked up in the file I was working in, but I'm moving on until I break stuff again.
I'm curious what happened, if anyone sorts it easily, but don't burn cycles solving a problem nobody has.
Thanks.
joel
The content of the file is clipped. If you go into outline mode you can see the green clipping path, and the black outline of the shape. When you apply a clip, only the areas inside the clipping path remain visible. In this case the clipping path is completely separate from the shape, so clipping has the effect of hiding the shape entirely.
Pay a lot of attention to the status bar in Inkscape. In this case, selecting the black shape in outline mode shows "Path 10 node; clipped..." which was enough to immediately indicate the problem to me.
Ah. I'll watch the status bar more, though I saw that message and it didn't mean anything to my beginner's brain.
Thanks for the update. Easier to resolve human error going forward than chase down a bug.
I thought that the mention of "clipped" in the status bar might jog your memory, as presumably you'd applied the clipping path in the first place. But if it was as a result of just clicking round and experimenting, I can understand that it may not have registered consciously.
With regard to the clipping in your file, select the black item in outline mode and right-click, then choose "Release clip" from the context menu. Voila, your objects are visible once more.
You might find some of my tutorials in Full Circle Magazine useful. The magazine is a free download. There's an index of articles here: http://www.peppertop.com/blog/?p=1563
Part 13 (FCM #73) covers clipping, for example.
Yes, I was clicking around doing all kinds of things without paying enough attention. Years of experience with AutoCAD and Photoshop gave me a false confidence about Inkscape. I've dialed that setting back a wee bit, and I'll be rummaging through all the articles (h'ray!) and enjoying a couple rants about The Cure and Blur (with which I concur entirely!)