Micro-gaps between mesh components

[Orwar]

   I'm working on a mesh project that's going to contain 3 components - I've finished all my mesh models and uploaded them into SL. I've made each component modular for ease of use and everything seems to be working pretty well so far, except for one minor detail; in SL, I see a minor, flickering edge between one component and the next, a thin black line that's so small it was hard to even get a shot of it - I don't know if it's SL, or if I've gone mucked up somehow in Blender whilst rotating, but looking in Blender all the angles and lines are completely identical on both ends of the piece. 

   Seeing as the mesh is snap-fitted, and all the dimensions are fine according to both the in-world build tools and in Blender, I'm wondering if it's a limitation in SL's rendering capability or if I've gone goofed somehow. The lines aren't always there, and only show from certain angles. Other than that they appear to fit perfectly.

[Fionalein]

You could try making it overlap a bit 1 or 2 pixels of texture wide only... I have no idea what it is but I have seen similar in Prims so I always let them overlap slightly.

[OptimoMaximo]

it's most likely a vertex normal issue. To fix it, you should make sure that those lines of overlapped vertices share the same vertex normal orientations, or the lighting will make that line be visible (reason why it is visible only from certain angles). If you're exporting the pieces to one single file, there should be an option to weld the vertex normal of adjacent objects. instead, if you want to export the various pieces separately, you can try and edit the vertex normal, but i don't know whether Blender has this tool. If it doesn't, join the pieces together, merge the overlapping vertices so that their vertex normal get unified and split the parts back, so that the newly recreated rows of vertices share the same vertex normal orientation.

hopefully this helps 🙂 

[Chic Aeon]

While it COULD be  a vertex normal issue, from your screenshot it looks to me more like some vertices that "should" be welded are not OR you have vertices that are not aligned and so not all that easy to weld together.  For the best inworld look your mesh object should connect vertices together and not leave any just "out there" :D.   If you post a shot of the model it will likely be more obvious what the problem is. 

 So for example (without making one) if one side of your flat panel (wall?) has extra edge loops used for window openings for example and you don't have the same on the piece connected so that you can WELD them together as one -- you see this problem.

You can ad single vertices along the edge as needed and then weld to that.  

Good luck!

 

[Orwar]

   I see - I'm going to have to look into vertex normals, however I can't weld them as they're very much designed to be separate. They're snap-fit and made to be sold as modular pieces that ideally would be compatible with any room. By welding them, they... Won't be very modular, anymore. But it's only on this part, the other two sections go together without issue.

   I'll see if I can figure out the vertex normals - I -did- rotate in that piece so it sounds like it might be it.

   Thank you!

[Kyrah Abattoir]

Also keep in mind the higher you are the more visible floating point rounding errors are.

[Bitsy Buccaneer]

11 hours ago, Orwar said:

   I'll see if I can figure out the vertex normals - I -did- rotate in that piece so it sounds like it might be it. 

Because it's an easy mistake, both to make and correct, which can have strange consequences on uploading - it might be worth double checking that you did the Apply > Rotation thing too.

[ChinRey]

On 1/13/2019 at 7:04 PM, Orwar said:

   I'm working on a mesh project that's going to contain 3 components - I've finished all my mesh models and uploaded them into SL. I've made each component modular for ease of use and everything seems to be working pretty well so far, except for one minor detail; in SL, I see a minor, flickering edge between one component and the next, a thin black line that's so small it was hard to even get a shot of it - I don't know if it's SL, or if I've gone mucked up somehow in Blender whilst rotating, but looking in Blender all the angles and lines are completely identical on both ends of the piece.

Make sure the overall dimensions of each part is an even numebr of millimeters. That solves msot of the "unsolvable" alignment problems.

[Orwar]

12 hours ago, Bitsy Buccaneer said:

- it might be worth double checking that you did the Apply > Rotation thing too.

   The what thing? I duplicated the profile line, snapped my cursor to the far back bit that was in the corner and rotated the line 90 degrees with the cursor as my centre point. 

56 minutes ago, ChinRey said:

Make sure the overall dimensions of each part is an even numebr of millimeters. That solves msot of the "unsolvable" alignment problems.

 

   Yeah, I've gone over the lines and angles and all of them appear to be in order. 

21 hours ago, Kyrah Abattoir said:

Also keep in mind the higher you are the more visible floating point rounding errors are.

   It appears this may have been it; I tested it in my skybox. Went down to the ground level and I'm not having any issues with it here.

   Actually as I was writing the responses and testing it at the ground level I realised that I wasn't using the same setup as in my skybox - I'd gone from an inside corner straight to the outside corner, so I put down an inside corner to the straight - and there were the flickering lines. I guess I was looking for the problem in the wrong piece. I'll go have a look at that one instead.

[Chic Aeon]

To answer a question above about applying rotation --- a pro told me five or six years ago to ALWAYS apply Rotation, Location and Scale before exporting the file.  This is a rule for me now and has solved lots of issues. So far it seems like a good plan for most things in SL -- I haven't found any problems. 

Sounds like you may have it worked out your gaps -- but, from all this conversation it sounds like the final plan may not work as well as you suspect --  IF you are planning on selling these.  Most folks don't have "builder skills" or just minimal ones (placing furniture say) so I am not seeing how your modular build -- which has to be VERY exact it seems will work for sales. It sounds like a support issue waiting to happen ^^. Many of us like to avoid those at all cost LOL.   Maybe something with some paneling edges that don't need to be so precise would be better for the regular folks. Not everything we WANT to make here is practical -- sadly. 

But best of success and I hope it works out as you want it too. 

[Orwar]

5 hours ago, Chic Aeon said:

To answer a question above about applying rotation --- a pro told me five or six years ago to ALWAYS apply Rotation, Location and Scale before exporting the file.  This is a rule for me now and has solved lots of issues. So far it seems like a good plan for most things in SL -- I haven't found any problems. 

Sounds like you may have it worked out your gaps -- but, from all this conversation it sounds like the final plan may not work as well as you suspect --  IF you are planning on selling these.  Most folks don't have "builder skills" or just minimal ones (placing furniture say) so I am not seeing how your modular build -- which has to be VERY exact it seems will work for sales. It sounds like a support issue waiting to happen ^^. Many of us like to avoid those at all cost LOL.   Maybe something with some paneling edges that don't need to be so precise would be better for the regular folks. Not everything we WANT to make here is practical -- sadly. 

But best of success and I hope it works out as you want it too. 

   Oh, but the rotation will depend on the direction of your build - scale and location both work off of the centre of the grid and has been made in 1:1 through and through; 1 mm in Blender = 1 mm in SL. People who don't know how to snap to grid probably shouldn't be buying construction components to begin with, unless they're ready to read the instructions carefully and/or experiment their way until it works. If you buy a piano, you don't complain to the manufacturer because you don't know how to play it. I agree, the consumer attitude in SL can often appear rather entitled and, to be blunt, a little stupid; but if every creator was to simply give up because they're afraid people will whine at them or give them bad reviews, well, SL probably wouldn't be around.

   I found the error in the mesh, it wasn't on the piece I was looking at, but the piece adjacent to it. I see no reason it shouldn't work once I've re-created the faulty piece.

[Kyrah Abattoir]

A smart thing that some component creators do (in SL but also in the game asset world) is that they have seam pieces that are part of the different sections that you assemble that essentially hide the joining point. This also has the benefit of giving a bit of leeway to the end user for the final assembly when they are constrained by an existing structure.

This is what i'd call a bad example as the joining has to be perfect.

This, in my opinion is a much better approach and is probably a more useful kit in general. But it's also part of the style.

[Bitsy Buccaneer]

13 hours ago, Orwar said:

   The what thing? I duplicated the profile line, snapped my cursor to the far back bit that was in the corner and rotated the line 90 degrees with the cursor as my centre point.

In Blender, in Object Mode - Object > Apply > Rotation, as shown below. Location and scale too if you've changed those as well.

Things can look fine in Blender but then behave oddly when uploaded if any rotation, location and scale changes haven't been 'applied' to the object in Blender. It's easy to do so it's a useful routine to get into before exporting your work. Easy enough that IMO it makes sense to rule it out early on when troubleshooting.

Edited January 15, 2019 by Bitsy Buccaneer

[Orwar]

3 hours ago, Kyrah Abattoir said:

This is what i'd call a bad example as the joining has to be perfect.

   Yes, if the objects look like that, and have an object size that is irregular - which is something I've come across with plenty of 'modular' building components - putting it together can be Hell and a half. Especially if the curved section's connective bit is arbitrarily off centre, as they quite certainly will be if the mesh isn't anchored in its object boundaries.

3 hours ago, Kyrah Abattoir said:

 

This, in my opinion is a much better approach and is probably a more useful kit in general. But it's also part of the style.

   Where applicable, I agree. If the long stretches of outer walls were to have no posts, I think it would be aesthetically unbalanced - and it certainly makes it easier to eyeball it together. However, the opposite may be true for something that you want to be subtle. I'll consider adding a joint nonetheless, for those who prefer to use them.

47 minutes ago, Bitsy Buccaneer said:

In Blender, in Object Mode - Object > Apply > Rotation, as shown below. Location and scale too if you've changed those as well.

   Thank you, I'll give that a try!

[Bebe Bunny]

My mesh body has this kind of gap but I always assumed it was more about my graphic card or how close I was to it to see the lines.

[Beq Janus]

As noted above the height issue is the first thing to check. In these types of problems, my first advice is always to rez the items at sea level and check again. Rounding errors do occur and can affect all rotation and positional operations. Build platforms, despite their popularity, are in general, not the best idea we ever had as users 🙂

As @Orwarnoted scale affects these too. It all comes down to playing nice, When the viewer draws an edge on the screen it is a series of pixels in an approximation of a line, the length and angle of the line determine where the steps in the line occur and have lines of different lengths is asking for trouble. Similarly, within a mesh asset, all coordinates are stored as 16bit signed integer values (your mesh is effectively snapped to a grid of 65536 (64K) points when you upload it. If one part of your build was 64m high then the resolution of the points within it are quantised to just under 1mm (or to be exact to 1/1024th of a metre), while the 6m high piece next to it has 10 times that "internal" resolution. There are rounding and scaling operations taking place at all levels of a 3d scene, being aware of some of this can help you design your products to work with the renderer more smoothly.

Another common source of these is related and comes from bad topology, in particular from unconnected vertices. This gyazo shows an example I helped fix a few weeks back. In many cases such as the one below, the user is not intending to butt things up together and simply needs to change the construction (this build was prim2mesh it actually had more verts than I've shown but none of them were  aligned/merged), when you do need to then carefully thinking about the design will save you a lot of pain.

 

Edited January 15, 2019 by Beq Janus
Corrected stupid unit error ~1mm not ~1cm (good spot Optimo)

[OptimoMaximo]

1 hour ago, Sylvannas Zulaman said:

My mesh body has this kind of gap but I always assumed it was more about my graphic card or how close I was to it to see the lines.

That's another issues that has to do with rigging, actually

[Christhiana]

I've found that aligning things high up in the sky or at a sim corner will often not work properly. I would get round off errors. Mostly items rotating slightly by themselves. I would correct them and a few days later the errors were back. I used to build on a platform at 1000m above my shop which is at the corner of a sim. I have bought a small parcel away from my shop that is not at a sim corner so I can build at ground level. I haven't had any alignment issues since.