I've been going through a lot of portfolios for people creating game assets, and I've noticed that some of the pieces to a whole object arent fully connected by polys, they're just kinda "sitting/ floating" in the main piece. Is it ok to not have every thing fully connected in a model? For example, take a look at the SCAR that this guy created:

http://www.mikebrainard.net/IMG/fnscarh_wires.jpg

If you look closely, you will notice that some pieces aren't connected.

Is it ok to do that, especially if you are putting it into a game engine, such as UDK?

Is it ok to do that, especially if you are putting it into a game engine, such as UDK?

Yup

As long as they're merged under one mesh for one draw, then yes, it OK.

Wow I had no idea... since I started modeling a few months ago, I've been trying to make sure that everything was fully connected. Now with this knowledge, I can save some polys! Thanks guys!

Save some polys, sure, but you'll also save countless scores of man hours.

Its certainly not essential,you need to use your judgement as to when its worth the extra polycount. you can see if you look at the linked model that where the mesh is floated there is a harsh seam between the elements.

Here are some advantages of modeling solid

Baking setup is easier:
If you have a solid mesh there is rarely any reason to explode the mesh before baking. since there is no overlapping you just push the cage out and bake.

Baking results are better:
Since the entire mesh is solid you get much better quality concave bevels. when you split the mesh you tend to miss information when you are baking which creates seams and other artifacts. (these meshes could be much more optimal)

Also keep in mind that these problems get worse when the texture mips




Less Wasted UV space:
Because your not putting geometry ontop of geometry you end up with less invisible uv space.

Baking results are better:
Since the entire mesh is solid you get much better quality concave bevels. when you split the mesh you tend to miss information when you are baking which creates seams and other artifacts. (these meshes could be much more optimal)

Also keep in mind that these problems get worse when the texture mips

This is the part I don't get. In an example like that, there's practically a 90' angle between the two parts, with the length of the cylinder being pretty long. So there's a good chance that they're going to have to be on separate UV islands anyway (especially in OP's example, where many of the knobs are more complicated in their nature and could also move around for animation, meaning they'd be physically seperate in reality). So wouldn't the UV map usage and mips be the same?

The seam on that example also looks a bit exaggerated towards bias too, as if no padding was used?

The padding won't change anything as the plane isn't cut anywhere.

Originally Posted by cryrid

This is the part I don't get. In an example like that, there's practically a 90' angle between the two parts, with the length of the cylinder being pretty long. So there's a good chance that they're going to have to be on separate UV islands anyway (especially in OP's example, where many of the knobs are more complicated in their nature and could also move around for animation, meaning they'd be physically seperate in reality). So wouldn't the UV map usage and mips be the same?

The seam on that example also looks a bit exaggerated towards bias too, as if no padding was used?

Im not advocating merging moving parts, just saying there are advantages to solid modeling, and making sure new modelers are not dismissing it.

The UV split doesn't change anything. the error is because the rays are not cast from a continuous surface. the cylinder and the plane are cast separately so you miss details and get a seam. (this is the same thing that happens with smoothing groups and ray distance)

Like Noors said about the padding, the renderer wont pad that area as it will pickup the high poly plane underneath and return the normals from it, again creating a seam. also FYI both maps were rendered with loads of bleed and 64 pixel padding.

Setup that example and bake it yourself if your critical.

The UV split doesn't change anything

It changes the part where you say that polygon islands wastes UV space. If the island has more surface area than you can cram into the same UV island and get away with, then the UVs are going to wind up being pretty identical?

Setup that example and bake it yourself if your critical.

I did, and I've seen quite a few examples of it being done and looking swell without sudden black lines highlighting the difference. Hence my confusion.

A UV seam doesn't matter. What matters is a hard edged seam from having two intersecting meshes. With a "merged" model you will never get that, with intersecting models you will always get aliasing.

What Fletch is saying is entirely correct. Just look at his example. The less hard intersections the more seamless and "highpoly" your bake will look.

If you've got a complex mesh, the UV savings really start to add up, and you can cram random little bits into the "uv holes" created by merging bits together.

If you have split objects and bake them without explode baking, you can get some really nasty errors. Especially on complex meshes(ie: not a simple plane) where your mesh normals will be bent and the two objects simply wont match up without extra geometry to soften the normals(at which point any savings from split meshes is lost).


Personally I merge as much as I can, splitting meshes where things need to animate, parts can be toggled on/off or where bakes with become really complex and produce errors(complex overlaps etc).

Can you make nice looking meshes with lots of intersections? Sure, but it won't look as good, it will be more work, it will be less efficient with UV space, and it won't really save you many verts(which is generally the important thing, not triangles).

So whats the big benefit to doing it? Saving a tiny amount of time while doing the initial lowpoly modeling work?

I'm not saying the result of a merged mesh wont look superior if you take the extra time to work on it, I just don't see it saving any UV space if the UVs need to be split anyway, nor do I see the connection point looking so unacceptable.

Originally Posted by cryrid

I'm not saying the result of a merged mesh wont look superior if you take the extra time to work on it, I just don't see it saving any UV space if the UVs need to be split anyway, nor do I see the connection point looking so unacceptable.

In the split version there is a circular area in your uv tile which is dead space. In the merged version there is a circular hole which you can put other uv islands into
It may seem like a small saving but it adds up
the only way to use the space in an overlapping mesh is to do 2 bakes and merge them after the fact.

Originally Posted by r_fletch_r

In the split version there is a circular area in your uv tile which is dead space. In the merged version there is a circular hole which you can put other uv islands into

Unless I'm misunderstanding what you're trying to say here, you can use the overlapped space of a split model just as well to put other UV islands into; it'll just have that other bit of texture underneath your overlap, but you can't see it on the model anyway. That said, it is a bit more troublesome to do, since you'll have to bake twice and combine your maps, I think.

Originally Posted by Zwebbie

Unless I'm misunderstanding what you're trying to say here, you can use the overlapped space of a split model just as well to put other UV islands into; it'll just have that other bit of texture underneath your overlap, but you can't see it on the model anyway. That said, it is a bit more troublesome to do, since you'll have to bake twice and combine your maps, I think.

yup

Originally Posted by Zwebbie

Unless I'm misunderstanding what you're trying to say here, you can use the overlapped space of a split model just as well to put other UV islands into; it'll just have that other bit of texture underneath your overlap, but you can't see it on the model anyway. That said, it is a bit more troublesome to do, since you'll have to bake twice and combine your maps, I think.

Yeah I really wouldn't bother with this, it would be way way more of a hassle than its worth, plus weird mipping issues and things of that nature, really not a good idea.

Originally Posted by cryrid

I'm not saying the result of a merged mesh wont look superior if you take the extra time to work on it, I just don't see it saving any UV space if the UVs need to be split anyway, nor do I see the connection point looking so unacceptable.

the UV's need to be split anyway, yes, but there is no extra space to UV where the mesh protrudes into the other mesh. Theres going to be extra space no matter what if you split the models because you need to have mesh padding so that the edge of the mesh you are inserting into another mesh doesnt show.

while this amount can be pretty negligible, it can add up.

Originally Posted by r_fletch_r

In the split version there is a circular area in your uv tile which is dead space. In the merged version there is a circular hole which you can put other uv islands into
It may seem like a small saving but it adds up
the only way to use the space in an overlapping mesh is to do 2 bakes and merge them after the fact.

this also, so i guess you just would add the top of that cylindar to the circular hole and have the side of the cylindar somewhere else as a UV island

Originally Posted by cryrid

I'm not saying the result of a merged mesh wont look superior if you take the extra time to work on it, I just don't see it saving any UV space if the UVs need to be split anyway, nor do I see the connection point looking so unacceptable.

Your main problem is you think this takes a significant amount more of time to do. The extra lowpoly modeling should be extremely fast to do, and it saves massive amounts of time dealing with bake setup etc(especially doing test bakes, revisions, etc it really adds up). In reality it SAVES time.

Practice your modeling a bit if you would spend that much time merging meshes together. =P

would be very time consuming and a nightmare if every model was made from 1 solid mass i would think..

everythings in sections and makes it more managable..

am no 3d expert tho and pretty much amature at it but am sure thats the case

Originally Posted by cdavidson

would be very time consuming and a nightmare if every model was made from 1 solid mass i would think..

everythings in sections and makes it more managable..

am no 3d expert tho and pretty much amature at it but am sure thats the case

You'd be suprised the time it can save actually. Since I've started merging i spend less time cleaning up my bakes.

You can always start with seperate shapes and merge at the end, most block outs I see are overlap heavy.

Your main problem is you think this takes a significant amount more of time to do

And your main problem is thinking the word 'extra' somehow means 'significant'.

I don't think this kind of modeling is significantly faster, merely I don't think it is as bad as it is being portrayed here.

Originally Posted by cryrid

And your main problem is thinking the word 'extra' somehow means 'significant'.

I don't think this kind of modeling is significantly faster, merely I don't think it is as bad as it is being portrayed here.

Hey, you can do whatever you want, create models however you want, whatever gets the job done. But when it comes to giving advice to others on how to do things, its important to look objectively at the pros/cons of different methods. When one method has many cons and few pros compared to another, why insist on doing it anyway, or suggests others do the same?

When one method has many cons and few pros compared to another, why insist on doing it anyway, or suggests others do the same?

Dude, that's not even the conversation. The guy wanted to know if every polygon had to be connected in game engines. They do not (as many games will prove), so that was my answer to him. I've yet to advocate one method over any other other, that just appears to be your assumption because I've been questioning the notion that such a practice instantly means a noticeable loss of UV space while creating large black seams around the connection. If AAA games are throwing out models that are made of several islands because they think the results are acceptable to them, I don't see how that warrants you trying to attack my own skill level?

Practice your modeling a bit if you would spend that much time merging meshes together. =P

:/

Is this really necessary?



Anyways, these things are so context and situation based, I feel like sometimes it does save you some time to not make every surface contiguous, and other times it's necessary.

I kinda agree with cryrid, it's not the worst thing ever, but you don't want it up in your face with something like say an fps weapon model.
I'd try to make the context clear for people learning this stuff, that there's no right or wrong way... just what works for when.