# Centroid calculations for Combined Solid Objects

By combined objects I mean objects with differing unit masses, and get the centroid of the entire assembly. I can do this in AutoCAD but it’s slow and not much fun - I have to use an ‘abstract’ model instead of the actual real-world geometry. And literally all I need is the centroid (for this particular task).

Is it possible in Rhino? Maybe with Karamba or another plugin? I can’t find an exact example of this on Karamba’s site, but only because I think the program goes way beyond that and therefore wouldn’t advertise a feature.

Note that I’m not a Grasshopper user (not yet at least). To be honest I’d rather spend money opposed to spending time on a GH script (of my own that is).

How many objects are we talking about? If it’s less than 5, you could do it manually by getting the centroid of each object and drawing lines and points in relation to their weight according to each other.

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PetersTools lets you assign densities to solids, and then find the center of gravity of a bunch of objects. Is that what you’re looking for?

Thanks Peter - that’s pretty much exactly what I’m looking for!

It’s less than 5 different unit weights, but roughly 100 objects. I can reduce the object count but that reduces the overall utility of performing the task. If not for that your line idea would be a pretty slick solution and would save me much of the tediousness of my first idea

My original idea was to resize objects based on their mass (hence the reference to the “abstract” model). I would just pick an arbitrary cross sectional size for say, the lightest element, and increase the cross-sectional areas of other members relative to their units weights. This was my method in AutoCAD. I’d then “Union” everything into a single solid (ACAD’s union will join solids even if they aren’t touching) and I could get the centroid in a single go. This is how I’ll likely verify whatever method I find in Rhino is correct. The drawback I found with this method is that I’ll spend time modelling something I can’t re-use for anything else.