Mesh Combine

# 1 19-04-2012 , 09:33 PM

Registered User
Join Date: Mar 2012

Posts: 31

Hi, very noobie question, but I was just wondering is it always better to combine objects in a mesh with adjoining edge vertex's or can you just merge them into each other like in the example, just want to know for when if making a complex model it could save on time

Thanks,

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# 2 19-04-2012 , 09:51 PM

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You can often leave them as separate objects. I'll let a more experienced modeller provide better advise.

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# 3 19-04-2012 , 09:55 PM

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Join Date: Jan 2004

Location: Michigan, USA

Posts: 2,998

Let me know if I understand your question...

You want to know if it is better to combine objects (mesh>combine) (the objects remain separate) or unify the objects into a single mesh?

That really depends on a lot of things, the most critical of which would be how close will the camera get to the objects and how long they will be in shot and how well lit they are. If the camera is sufficiently far from combined objects you will not notice the lack of the natural bevel that would exist on a unified part.

Also, components that have their junctions covered may be combined to save the time and effort it would take to combine them.

For close shots unifying objects would have the most realistic appearance. Light will reflect off the junctions of the object and look more natural. However, you need to consider the extra time needed to combine and then route geometry to be able to smooth the objects.

Scale effects alot of this too. For a gigantic 60' tall robot you are not going to notice whether a 2' square gear box is made of of 50 parts just stuffed into each other that would take you 3 minutes to assemble or the same part as a unified mesh that took 3 days to work out the topology.

In your example images above, if you intended to smooth that unified cylinder and box you would need to add support edges and would have to deal with puckering in the corners of the box/cylinder junction or creasing of the cylinder as a result of any support edges that ran the lengthwise.

So it really just depends. The camera distance, model scale, technical requirements, lighting, speed of the object in the scene, time the object will be in shot....

I know it's kind of a "cop out" answer but it's the best I can come up with. If I had unlimited time, don't know how close the camera will ever get to the shot, the geometry is not insanely complex, than I strive to unify and smooth as this will give the best result in all possible situations. But in production it's always a balance of time vs accuracy.

Maybe Jay would have a more meaningful opinion as he works in the film and entertainment industry and is always having to struggle with the time vs accuracy dilemma. So he might have some more structured rules for when to unify vs when to combine.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 19-04-2012 at 11:08 PM.

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# 4 19-04-2012 , 10:58 PM

Technical Director
Join Date: Feb 2004

Posts: 2,988

As Rick said above, it all depends. I generally like to merge my meshes together if they're part of the same object, but again, that takes time, something you don't have much of in production. I also like to do it as it keeps the scene clean in the outliner. If you're doing this for a personal project then go for it.

The only problem I've ever seen crop up when not combining objects, is when the two intersect. Some renderers, or techniques, may cause artifacts in those areas. It's also more of a pain to UV the model, as you have to keep jumping back and forth between the objects to make sure nothing is overlapping. Painting skin weights on multiple objects can be a pain as well.

Rule of thumb with everything in 3d: Deal with it later. If it causes a problem later on, fix it then user added image

As you get more and more experienced, you'll be able to preempt these problems, which will make you more efficient.

Imagination is more important than knowledge.

Last edited by NextDesign; 19-04-2012 at 11:01 PM.

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# 5 20-04-2012 , 10:28 AM

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Join Date: Jan 2012

Posts: 43

It is more and more frown upon, or totally forbidden in the industry to have intersecting objects.
There is a third solution, to cut the penetrating one and move the vertices as close as you can to the other surface.

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# 6 20-04-2012 , 12:32 PM

Technical Director
Join Date: Feb 2004

Posts: 2,988

There is a third solution, to cut the penetrating one and move the vertices as close as you can to the other surface.

Originally Posted by yoruneko

I have never seen that in production. That would cause horrible artifacting in renders, especially with raytracing.

Imagination is more important than knowledge.

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# 7 20-04-2012 , 01:03 PM

Lead Modeler - Framestore
Join Date: Feb 2003

Location: UK

Posts: 6,287

Swings and roundabouts. It really depends on the model and the time you have and what its for, how close is it going to be seen and so on

its a case of thinking about the topology, will you benefit from extruding say an air intake/scoop on a surface because it is moulded or shall I model a separate scoop with a nice bevelled edge and sit that on the surface so the light pick up the edges...this of course would mean intersecting geometry which is acceptable and for the most part unavoidable. Depends on the detail and the type of design you are doing.

You could build say a piece of footwear like a boot as one object and cut in the detail, or even use dispalcement, or if it is to be a high res boot then I would make it out of say four to five pieces of geo with nice edges and place them all accordingly, so you would have the sole, heel, and then maybe three bits of geo for the upper leather which would consist of the main leg/calf leather, heel leather and finally the main foot area at the mid going to the toes.

So as I said, with all in one meshes you have to think about the edge loops keeping the flow right, no odd geo and bevel to make edges sharp if need be, whereas with separate geo you still need to to keep the geo looking good but if the geo intersects just delete what you arent going to see. Plus the fact you arent going to worry about matching the geo edge for edge and so on...

to cut the mesh though and place the verts and snap them to others is pointless, firstly because it wont render correctly but also you may as well just merge into one mesh.

hope this helps

J

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