Monomesh Question(noobish)

d1ver · Aug 2008

Hey,everybody,whatsup!
I'm pretty much in a need of advice here...
Well,I'm supposed to model a building and it is supposed to be a monomesh.Being simple I consider a monomesh to be an object which has only one element as subobject,the meshflow is never interrupted throuhgout the whole model.Giving it a thought I came up with one thing that bothers me.Basicaly you can make any two elements of an object have one common edge,so they would be one element,as shown on picture "A".

The wall and the prortruding object are connected only by the edge number 1.There's a gap between edges 1 and 2,but if I pull edge number 2 underneath theese little arces the gap won't be seen.So everything will look as intened without any significant number of triangles used.
BUT,most of the examples I've been shown look more like picture "B",where all the werticles are welded into the mesh.(I didn't weld it all on this picture,just a couple of them to give you the idea).
Even knowing, that game engines could be significantly different I ask you to give me any comment on that.If you think that this is appropriete or not and how may it affect anything in any way.

I thinks that it's still monomesh and everything should be okay,but I really don't want to mess up with this one,so you can never be to sure.

Looking forward to any answers and Thanks in advance!

MoP · Aug 2008

Usually if a game engine wants everything to be a solid mesh, it's because of performance reasons (mainly shadow casting or collision detection).

The model you show in image B. is a really nasty mesh - it looks solid but it isn't. This could be bad in an engine. Usually what I'd do is either make the protruding part completely separate and solid (not attached to the wall behind in any way), or actually connect it up fully.

To be honest, it's only an extra 8 or 10 triangles if you do it that way anyway, and the end result will be more predictable and easier to work out what's happening just at a glance.

renderhjs · Aug 2008

what is a monomesh,- never heard of it, googled for it and came to this thread again back.

If you want to save triangles and work:
- build the wall as flat rectangle and attach the window/door decoration

why do you need to cut several into a face when you wont see a difference in the end and you could as well go with just 2 triangles (a rectangle)

d1ver · Aug 2008

MoP ,
Thanks,well just as I thoguht.I'm gonna do it all solid,but still,I'm just interested if "A" is appropriate or not.I've read somewhere,that even different smoothing groups slow performance of a game engine(the guy there discussed renderware as far as i remember). may be the engine would just process elements in different passes.And if element is considered as a diferent object(or just a different bunch of vertices) and I for example have 20 pertruding parts in a single building then there's gonna be a whole lot of "objects" in a single scene and it's gonna be harder for a GPU.And if a different structure is created so store ever single "bunch of polygons" then it'll be a hit on free RAm memory too.
Well.It's as far as I am able to think of it.If I am in any way correct then method "A" woulnd't be all that bad.But I don't know about shadow casting and colission in that case.
About "b" not being a solid mesh:"(I didn't weld it all on this picture,just a couple of them to give you the idea)".
I just hoped I won't have to do this=)

renderhjs,
yeah,I tried to google it too,but didn't find a thing=(
that's just what the guys i'm doing a test task for told me.I thought I was that noobish not knowing what it is...
The first test I did just as you said.Attached stuff and bla-blabla...
Then I showed to the Lead Art of the studio and he said that it wasn't monomesh.i was like wtf%\ but man...I have no choice and have to redo it,'cause I need a job and we only have just a couple gamedev companies in belarus and none of the are hiring wright now,except for this one...

Sage · Aug 2008

If they want a water tight mesh that usually means no holes in it. I had to do this and the reason given was how shadows worked. If the model isn't solid the engine doesn't cast shadows properly. A would be terrible. Not only would the model have holes in it but odd polygons. And the smoothing would be wrong, but that would depend on the engine. Anywhere where there are holes there would be a hard edge. I did what Mop suggested. If you are lucky that is all you have to do to make it work for your project. I would ask the lead again if what Mop said is good enough for their needs since it's way faster than having to account for mesh flow.

Alex

renderhjs · Aug 2008

but that is a pain in the ass to work for when you want to work for example with modular building blocks - because in the end they will be placed intersecting at times into each other - will this cause also errors in those engines?

MoP · Aug 2008

renderhjs: Depends on your engine. The one we work with always does a compile process to generate decent mesh data for a level. Obviously you can supply a mesh which isn't watertight/solid, and it will work in game, it's just not optimal for performance and you may get visual artifacts with shadows if seen from certain angles.

renderhjs · Aug 2008

thanks for the answers guys, I wasn´t aware of all that.

d1ver · Aug 2008

neither was I
thanks a lot everybody

Jeremy Lindstrom · Aug 2008

So is monomesh just another name for contiguous mesh?

danr · Aug 2008

this is an art test? There might be no technical reasons for a watertight mesh other than to see if you can do it effectively without pissing away loads of polys - it's a good way of testing consideration for your poly usage while imposing a tight restriction. Anyone can do a low poly building by intersecting elements, but a really good watertight mesh brought in to a budget should show that you can make clever choices with shape and detail

well, thats one possible reason anyway

i once did a bunch of buildings like this so i could rig and animate them in cartoony dancy ways without them falling apart around seperate elements, it was actually really good fun. Contest!

Monomesh Question(noobish)

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