Is it safe to assume the number values shown in the various panels (command options window, attribute, channel editor, etc are also maya units?)

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I am constantly being thrown of by the number values displayed in these various editors, such as the attribute editor, channel editor, command options window, and so on.

What are these number values relative to anyways? For example with the command Merge command (Edit Mesh > Merge), the threshold parameter, does a value of 1 correspond to 1 maya unit, and 0.5 is half of a Maya unit?

For example, past hour I have been trying to get a understanding for the threhold value of the merge command. I created a plane, scaled up by 10 uniformly, and then removed a edge loop, which means that some of its quads are 1cm by 1cm (squares), and others are 1cm by 2cm. When I select a mix of points that are distanced by 1cm or 2cm from one another and merge with a threshold of 0.5, all points are merged into one.

This is unexpected to me and completely confuses me. Doesn’t the merge command essentially mean “of the selected points, merge any vertices that have a distance of 0.5 cm or less to its neighbour”? So in my test, when I provided a value of 0.5 and “always merge for two vertices” unticked, I was expecting nothing to happen, since all vertices have a distance of 1cm or more between them.

Am on Maya 2025, my maya units are set Centimetres (the maya default),

Any help would be greatly appreciated!

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You should try repeating this test, but Freeze the Transforms of the scaled plane before you do the merge. I don’t know for sure, but I’m guessing the merge tolerance (which is a “distance”) is operating on the local mesh, not the scaled result.
But to answer your general question, many different functions require tolerances that are not simple distances, but relative percentages or factors of some other criteria, depending on what the function is doing, or operating on. A simple example is bevelling, where the obvious understanding of a certain tolerance would be the size of bevel, but it’s actually an angular tolerance, and then is the value degrees or radians? or maybe even it is based on the Dot Product…?

tl,dr; it’s sometimes hard to know, unless the tooltip or docs explicitly tell you.

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You should try repeating this test, but Freeze the Transforms of the scaled plane before you do the merge.

And sure enough, it worked! :smiley:
So that is what Freeze Transforms is for!

Also thanks for the answer on the other more partinent question. That actually makes a lot more sense, I will keep this in mind going forward for sure, cheers!