What is the purpose of these "extra" cubes

[Chic Aeon]

I have been noticing these lately. Sure that they aren't a new thing, but what ARE they are why are they there?

This is nothing that is scripted like a hinge on a door. They appear in all sorts of H and G items. Just wondering LOL.  Thanks.

 

[Rolig Loon]

H & G?  As in Home & Garden?  Hang & Glide?  Happy & Gay?

My guess is that they really are handles for the book covers, which are separate prims that could be scripted to open if you wanted to.

[Chic Aeon]

Home and Garden (now you are smarter LOL).

Nice guess but this is ONE SINGLE mesh .5 li for all four books. Other things were even less likely to be scripted (like a table). So I am guessing that it has something to do with the SOFTWARE that was used. Likely not Blender.

So stay tuned as "someone" must know the answer

 

 

[ChinRey]

17 minutes ago, Chic Aeon said:

So I am guessing that it has something to do with the SOFTWARE that was used.

Or with whatever game it was ripped from.

[Chic Aeon]

1 hour ago, ChinRey said:

Or with whatever game it was ripped from.

I am thinking "no" on that. I see it from a lot of very good creators who have been around for a long while and who have very consistent styles.  AND it is differently slightly between the creators but there are always some extra cubes in there, sometimes floating, sometimes attached like you might do if you needed an extra prim for an animation.  

 

 

[ChinRey]

2 hours ago, Chic Aeon said:

I am thinking "no" on that. I see it from a lot of very good creators who have been around for a long while and who have very consistent styles.

It's hard to say for sure without examining the object closer but judging by the photo, that stack of book doesn't seem to be by a good mesh maker. It may be just the image resolution of course but all those staggered yellow lines look like a ton of wasted tris.

One trick makers of mesh bodies and high poly mesh clothes use to avoid the MAV_BLOCK_MISSING error, is to add one or more tiny cubes like these with a separate face to the mesh. It's been mentioned every now and then on the forums, for example in Vulpinus' reply to this thread:

 

I don't think anybody have been able to explain how adding more geometry can cure a problem that is caused by too much geometry in the first place but it does actually work.

An even bigger mystery is how on earth somebody can manage to make something as simple as a stack of books with a polycount so high it needs that trick but as I said, there seems to be a lot of superfluous geometry there so I won't rule it out.

Edited January 17, 2018 by ChinRey

[OptimoMaximo]

1 hour ago, ChinRey said:

One trick makers of mesh bodies and high poly mesh clothes use to avoid the MAV_BLOCK_MISSING error

MAV error is related to materials, not geometry. However, what i think this person did was to add invisible geometry in order to enlarge the bounding box artificially and obtain a better LoD by increasing the BB radius, letting lower LoDs kick in later/farther than they would have if the books were alone. 

EDIT: This is particularly true for indoor furnitures and objects. This way, you can zero out lowest and even the low LoD to lower LI, while the medium gets the same LoD as the high LoD. As a result, you get a indoor LoD stable model, intended to be put in places where the maximum viewing distance is capped by the room size. I have seen models made this way also make a linkset lower their overall land impact. Physics aren't a problem at this point: bigger objects can get a custom physics which wouldn't include the enlarging geometry, or it may be linked to something else and the new child can be turned as physics none.

Edited January 17, 2018 by OptimoMaximo

[OptimoMaximo]

1 hour ago, ChinRey said:

I don't think anybody have been able to explain how adding more geometry can cure a problem that is caused by too much geometry in the first place but it does actually work.

When you get animatable models online, you most likely find them as a native software file, where you might find groups and handles that work as parents. For collada, that's NULL GEOMETRY and it will export an empty transform, named after the group or locator (empty) that was the parent. MAV block is missing because there's a geometry that is empty though, there's no vertices to assign a material to, or there's no material to assign to the geometry block. Adding some geometry instead of the groups, assigns the unassigned material block to the new geometry, and the material/geometry match doesn't cause the error anymore.

VERY UNCLEAN practice, in my opinion

[ChinRey]

1 hour ago, OptimoMaximo said:

MAV error is related to materials, not geometry. However, what i think this person did was to add invisible geometry in order to enlarge the bounding box artificially and obtain a better LoD by increasing the BB radius, letting lower LoDs kick in later/farther than they would have if the books were alone.

That was my first thought too but why would they put them above the stack if that was the reason and why four of them? That doesn't make any sense at all. The common way of increasing the bounding box would be a single flat horizontal sheet at the bottom of the mesh. But of course, it doesn't make sense for the stack to be so extremely high poly it needs MAV_Block compensation either.

Then again, no matter which explantation is correct, that book stack is obviously not the work of a competent mesh maker. Maybe he or she had just seen those cubes in other meshes and added them without really thinking about it?

 

1 hour ago, OptimoMaximo said:

When you get animatable models online, you most likely find them as a native software file, where you might find groups and handles that work as parents.

That makes a lot of sense but it can't be the whole explanation. I have at least one outfit that I know were specially made for Second Life with Maya and the maker, who is a seasoned professional with lots of experience outside SL, still had to add several such cubes to be able upload it at all.

 

2 hours ago, OptimoMaximo said:

VERY UNCLEAN practice, in my opinion

You can say that again but to be fair, when it comes to commercial mesh bodies and clothing, what else can the creator do? The buyers demand the highest possible polycount and are oblivious to the consequences. So that's what you have to give them if yu want to sell much.

[OptimoMaximo]

33 minutes ago, ChinRey said:

That makes a lot of sense but it can't be the whole explanation. I have at least one outfit that I know were specially made for Second Life with Maya and the maker, who is a seasoned professional with lots of experience outside SL, still had to add several such cubes to be able upload it at all.

Instead, wihth this statement, to me it makes a lot of much more sense. You have to know that to export multiple material faces in Maya, you must have a plug in turned on for ANY exporter to account for multiple materials assignment, otherwise it exports one material definition only, with pointers to multiple, missing materials. Which is fine as long as you have to just move your content from a software to another. With Maya version 2015 this plug in was enabled by default, while previous maya versions had it in the list, just disabled. That behavior was most likely to result in mav blocks missing (vertex materials boundaries defined but missing the actual material definition, the block) and the work around was to assign those materials to other geometry in the export, so that they were written out as the single material pertaining to a single object. I found out this thing pretty soon, at the time, but i'm most technical on this stuff.

 

33 minutes ago, ChinRey said:

That was my first thought too but why would they put them above the stack if that was the reason and why four of them? That doesn't make any sense at all.

In a Blender perspective, it doesn't. In a 3DSMax scene, it does. Other softwares have proprietary objects/tools that can be exported as different node types, even as joints. Turning to geometry any NULL GEOMETRY item is common practice in 3DSMax. I had to work with a guy who used 3DSMax and what for him was a dummy object, when exported in fbx he changed them to locators (empty in Blender) for compatibility with my workflow. What if they converted all to geometry, thinking that a locator would convert to one single vertex when instead it didn't? Those four locators would have made a plane if they converted to vertices, making a overall bounding box that works, considering the lower plane being defined by the books, width , depth and height defined by this additional geometry. I'm with you that this guy might not be that experienced to know how the export would have been handled, and in the end the result they wanted was there. "who cares, as long as it works and i can sell it quickly" was the answer to the same question you had (why 4 cubes?)

 

33 minutes ago, ChinRey said:

But of course, it doesn't make sense for the stack to be so extremely high poly it needs MAV_Block compensation either.

AFAIK, material assignments (for SL meshes) are limited in the number of vertices per block, but i may well be mistaken here.

Perhaps @Beq Janus might have a tech explanation. I know that each material block is used to split the objects in submeshes during the upload. That might be the cause when polygon counts begin to skyrocket

Edited January 17, 2018 by OptimoMaximo

[OptimoMaximo]

Also, what if this guy used the 4 cubes as a mean for LoD reduction, removing 2 cubes for each lower LoD, or removing all the 4 at once just for the medium LoD and zero out the low and lowest LoDs? The uploader would see this as a lower number of vertices/triangles, while the books weren't actually affected at all.

[OptimoMaximo]

4 hours ago, ChinRey said:

It's hard to say for sure without examining the object closer but judging by the photo, that stack of book doesn't seem to be by a good mesh maker. It may be just the image resolution of course but all those staggered yellow lines look like a ton of wasted tris.

You can make a newly printed book with way less triangles, but those are a little worn and need to be bent and deformed. To me it seems it's not that big waste of triangles, considering the shape and the type of item the geometry is meant to depict. 

EDIT: not that the amount of deformation can be any noticeable enough from a distance to justify them in SL, but that's what you have to give your customers if you want to sell much (cit Chinrey)   and they want stuff that IF cammed in close have subtle details

Edited January 17, 2018 by OptimoMaximo

[Chic Aeon]

8 hours ago, ChinRey said:

One trick makers of mesh bodies and high poly mesh clothes use to avoid the MAV_BLOCK_MISSING error, is to add one or more tiny cubes like these with a separate face to the mesh.

OK. That could be it. I seldom get that error but when I have, it had nothing to do with too much geometry :D.   So the two things don't HAVE to go together but I understand that they certainly can.  

 

OK. I kept reading on this thread after replying and it was interesting. And I have to agree that for some of us details are important. "I" cam in a lot. However a lot of detail can be faked with textures (just like we did a decade ago :D).  I have to go back and FIND those books now (been decorating a sim so getting a little dizzy but I think I know where they are) and look a bit closer.   

Interesting conversation.  

Edited January 17, 2018 by Chic Aeon

[Chic Aeon]

So I went back to this book stack shown and to another that had one extra cube oddly at a corner. Neither seem to make any sense. The one with the open book and the cube at the corner was made by a full perm creator that I do not admire. The sell things with such obvious flaws (bad UV that have black areas showing (really?) etc.   

The other was made by (or listed as being made by) a fairly prominent creator who seems to put out good quality items. Now as said they both could be downloading models from the web and not cleaning them up appropriately. It had nothing to do with the weight of the meshes. They were fine. They were uploaded with (presumably) too high of LOD for the lowest (at least in my book) so they were a bit heavy LI wise. BUT the lods probably hold for the LOD1 crowd so if given a choice I would go with "heavy". 

 

I am pretty sure that some of the builders I know buy or download mesh and use it rather than making their own. It becomes obvious over time since one piece of mesh would be gorgeous and another something I might have made a few years back ^^. The person with this example seems VERY consistent in both work and style so I am having a difficult time thinking that they didn't actually make it. 

I also am having a hard time with four books needing to animate?  So like they would fall off the table neatly in this stack??? LOL.   So I guess we won't know.    

[OptimoMaximo]

4 hours ago, Chic Aeon said:

I also am having a hard time with four books needing to animate?  So like they would fall off the table neatly in this stack??? LOL.   So I guess we won't know.   

Thanks Chic, you just gave me a new idea for a plug in for Maya

[Chic Aeon]

5 hours ago, OptimoMaximo said:

Thanks Chic, you just gave me a new idea for a plug in for Maya

Always happy to help

 

[Beq Janus]

Looking back at the start of this thread my first assumption is aligned to what @OptimoMaximo said, that they wanted to boost the bounding box size so that the pile of books LOD switches at a higher distance. quite why they need so much geometry to achieve that is the only thing that makes me doubt that conclusion. 

Another thought would be that they were texture caching, again, for things such as imposter LODs...but then why would you put them up in the air and not bury them in the mesh. 

The mesh seems to be pretty well made (though the high LOD is pretty dense it is far from being bad) with reasonable LOD behaviour. So I think my first guess is closest but still...it's an odd way to achieve it. Curiously the 4 cubes have a texture face of their own.

Notice that at this scale the LOD on LL default LOD Factor switches at just 2.5m then 9.8m That is pretty reasonable for books that you might expect to be stacked in a room. Without the cubes, the bounding box radius would be less than half that and the LOD switching would occur far more rapidly, requiring the creator to invest more geometry in the LOW model. The question of "why 4 cubes" remains though. a single triangle on each extent would do just as well. 

So my theory is, the creator wants to have an object that is LOD resistant to a known distance and used those cubes to mark out the extents that they needed. after that, it does not matter how much of that volume the model itself uses it will still LOD switch at the expected distance. Just speculation but it makes sense to me for the most part. Note that they even have a deliberate physics shape that hugs the books.

 

 

Edited January 20, 2018 by Beq Janus

[Anna Nova]

11 hours ago, Beq Janus said:

 

 

Where on earth did that Edit panel come from?  My firestorm doesn't have those yummy mesh indicators.  Is this a 'yet to be released' version?

[OptimoMaximo]

13 hours ago, Beq Janus said:

So my theory is, the creator wants to have an object that is LOD resistant to a known distance and used those cubes to mark out the extents that they needed. after that, it does not matter how much of that volume the model itself uses it will still LOD switch at the expected distance. Just speculation but it makes sense to me for the most part. Note that they even have a deliberate physics shape that hugs the books.

Thanks for taking the time to inspect this case Beq. Another thing i thought, is that if the creator also wanted to make animated textures by switching them entirely, those transparent cubes could be used to hold the textures in cache, in order to animate the switch with no load time. I don't think this model does that, but this is an additional idea for that extra geometry.

[Whirly Fizzle]

5 hours ago, anna2358 said:

Where on earth did that Edit panel come from?  My firestorm doesn't have those yummy mesh indicators.  Is this a 'yet to be released' version?

It will be in the next Firestorm release, which all being well should be out next week.
If you want it now, join the Phoenix-Firestorm Preview Group (secondlife:///app/group/7ba4569c-9dd9-fed2-aaa7-36065d18a13c/about). The download link is the in group notices.

That feature was added by @Beq Janus who posted above.

[ChinRey]

4 hours ago, Whirly Fizzle said:

It will be in the next Firestorm release, which all being well should be out next week.
If you want it now, join the Phoenix-Firestorm Preview Group (secondlife:///app/group/7ba4569c-9dd9-fed2-aaa7-36065d18a13c/about). The download link is the in group notices.

That feature was added by @Beq Janus who posted above.

This is what we should have had right from the start when mesh was introcuded. Well done, Beq and Firestorm!

[iamyourneighbour]

Probably copied a la carte from whichever game it ripped from

[Chic Aeon]

On 1/20/2018 at 1:11 PM, Beq Janus said:

Note that they even have a deliberate physics shape that hugs the books.

My thought after we talked the other day was that this was an OK way to deal with nastly LODs (not so much on books which could have been more optimized but on some other types of items which could not) but I was assuming that having those floating cube would automatically give a nasty physics model so that you would have to walk OVER the books as if they were much larger. 

 

I just went over and tested and as you stated the physics model  is JUST around the books and you do not have to walk WAY above to get over them. 

SO HOW DID THEY DO THAT? It isn't a linkset that ignores the floating cubes. It is a single mesh. 

And yes that new panel looks spiffy. 

[Fluffy Sharkfin]

50 minutes ago, Chic Aeon said:

SO HOW DID THEY DO THAT?

Most likely by removing all but a single triangle/face from each of the cubes then using the Solid setting when analyzing the mesh to generate the physics model, since that ignores any part of the mesh which isn't "solid" (i.e. isolated triangles).

[Chic Aeon]

1 hour ago, Fluffy Sharkfin said:

Most likely by removing all but a single triangle/face from each of the cubes then using the Solid setting when analyzing the mesh to generate the physics model, since that ignores any part of the mesh which isn't "solid" (i.e. isolated triangles).

Except those are cubes, not triangles.  But I will try the solid with a triangle and see if that works -- just in case I need that some day :D.