Merging polys -- how?
Rainshine
Newcomer
Searching around turned up the topic linked down below, but I can't quite get it to work.
In my case, I'm working in CC3 trying to make a poly of terrain on an overland map with an edge that is a smooth curve, and an edge that's a straightedge trace against the adjoining terrain. My theory was to make two overlapping polys with the same terrain fill -- one with the straight edge trace against the neighbor, one with the nice curves on the outer coast.
It being two polys right now doesn't break anything, but it seems unduly complicated and could be futurely problematic. Trying to obey the directions in the old thread, the Trim Inside doesn't actually seem to trim their borders to abut; it doesn't seem to do anything, that I can tell. If someone could give me some pointers on how to merge the polys, or to otherwise achieve my poly edging goal, that would be lovely :)
Thank you!
Comments
Use the Multipoly tool
to combine them into one shape.
Two smooth shapes with different properties.
As long as they aren't touching, all shapes will be preserved as they are, but multipoly will make them behave as if they are one shape and impose universal properties on them. These two solid shapes took on the green colour picked in the palette and active in the Status Bar at the time the multipoly was created.
If they partially overlap you will end up with a hole where the overlap is.
If one lies within the other, the smaller inner shape will become a hole in the larger shape.
You can change the properties of a multipoly, but you can't edit the shape or trace it. To do either of those things you have to explode them again using the Explode button, which can be inconvenient. Unless there is a good reason for using a multipoly (for example, if you need to be certain that all the land of a global landmass will be affected if you change properties by picking once on any part of it), I recommend leaving the polys as they are - separate.
If they are partially overlapping, the simplest way to merge them is with the TRACED command. This will create a new poly, so delete the other two afterwards, and change properties on the new one if required.
The link below shows how to use TRACED. The example uses a single bitmap image, but it works just as well on a set of polys.
Getting polygons merged was the precise use case that TRACE was intended for, because I always want to extend my polygons just a little bit and I have always been way too lazy to try to trim edges or deal with multipolies. That it works on bitmap images was purely a happy accident.
TRACE works by making an image that has Working Image Resolution number of pixels along its largest edge from the selected entities and then tracing around the edges of the non-background pixels in that image to get a polygon. No matter the detail level of the input, the polygon output detail will be no more than the Working Image Resolution: incredibly detailed input with tens of thousands of nodes may get a little simplified, curves will become polygons (but generally a good approximation), and so on. TRACE will generally do a very good approximation of your input, but it won't work well on extremely thin shapes or very sharp angles. If it doesn't look good on the screen, it probably won't look so good after TRACE is done with it.
Having issued all of that disclaimer stuff, it's still almost always a good way to marge things. Maybe somebody will make some commands like UNION and DIFFERENCE directly combine entities without the hassle.
@jslayton claimed:
Maybe somebody will make some commands like UNION and DIFFERENCE directly combine entities without the hassle.
I've got UNION ready, but haven't gotten to DIFFERENCE yet.
Ooooo! Booleans!
:D
@jslayton
Maybe somebody will make some commands like UNION and DIFFERENCE directly combine entities without the hassle.
I'd be thrilled if you did -- I've put it up as a suggestion in a couple of threads before. It would make building complex outlines really easy.
I said somebody, not necessarily me. 😆
Lovely, thank you, that did it, and now I know some great new tricks. Thank you!
You're welcome :)
There's always more than one way to do a thing in CC3
With enough practice, I'll get this reading comprehension thing solved one of these days!
If you figure out how, let me know! I've been working on it for 50 years now, but it just seems to be getting worse lately.
For future reference for anyone reading this; I misread this quote. The command itself doesn't delete the two polys, that's left up to you as the user as Monsen points out. I was getting very confused where all these polys were coming from