Building Buildings

[IvyTechEngineer]

Hello

I have been interested in adding arches to cylindrical buildings in Second Life. I typically use the default SL viewer and only use Firestorm to save dae files and with Opensim.  My basic thoughts on workflow, if the building starts in SL, is to

1. build the basic structure in SL
2. export as a DAE file (using linked objects)
3. import into Blender and edit.
4. export as as DAE and upload to SL

I tried to edit the structures in SL but was unhappy with the results, i.e. the arch between the tunnel and the cylindrical walls had gaps.

Suggestions?

Thanks ivytechengineer 

[ChinRey]

50 minutes ago, IvyTechEngineer said:

 i.e. the arch between the tunnel and the cylindrical walls had gaps.

...

 

This is where you use the Knife tool in Blender. I'm not sure how familiar you are with it. Let me know if you need more detailed instructions and I'll try to post it - unless somebody else beats me to it.

[IvyTechEngineer]

Thanks ChinRey,

I had hope that I could do everything in SL. I am rusty with Blender but this forum has provided a lot of help in the past. I will take your advise to try to use the original and edit in Blender...

Thanks

[IvyTechEngineer]

Ok, I used the knife tool in Blender and then just deleted faces. It was a little tuff because I was using my laptop but got it done. I then uploaded the model and picked the options shown in the picture. I then  picked the Medium LOD for the physics model and uploaded but I cannot walk through the doorways or fly into the top and walk around to see if I could get to both sides. What did I do wring? OBWT - pasteall.org has retired, any good options to share Blender files?

[arton Rotaru]

Physic shape type is set to Prim?

Furthermore, make a very simplified physics mesh for it in Blender. Do NOT press the simplify button in the importer, though.

[benchthis]

At the time of uploading did you go to the physics tab and analyze your models physics? If not please see attached image for how I set my settings. Also when Arton mentioned changing the physics shape to prim this is important because even though after it's physics analyzed during upload, will not be able to walk through knife cuts unless after model is uploaded/right click model/edit click features tab & change physics shape type to prim. 

 

[IvyTechEngineer]

Thanks, I made a new lower prim physics model that is pretty good I think. I may even modify it a little and use it as the mesh. Not sure I want to spend the time to texture it or just try to do that in SL.

After all that work when I tried to upload I get the error message that I have "triangles that are too small"!  dang it : ) Looks like I have more work to do ...

 

[IvyTechEngineer]

tried again and got the same results after I simplified the mesh...

[Aquila Kytori]

16 hours ago, IvyTechEngineer said:

After all that work when I tried to upload I get the error message that I have "triangles that are too small"!  dang it : ) Looks like I have more work to do ...

 

In the mesh uploader's preview window you will find that the  "triangles that are too small" are indicated by thick black edges and vertices in the SL viewer and by red edges and vertices when using the Firestorm viewer. You may have to zoom in on the objects in the preview window to see them.

Then you have to go back to Blender, search the area of the physics model indicated in the mesh uploader's  preview window and get rid of them.

 

In the example below there are a couple of vertices at the cut-out for the tunnel that are causing there to be very narrow triangles when the physics model is triangulated.

When using the SL viewer :

 

Firestorm viewer :

 

Back in Blender, checking the areas indicated in the Preview window for the problematic triangles that are causing the errors :

 

When you think you have corrected the Physics model re-export and try uploading again. If you have no more errors then you're  done, if not its back to Blender and more searching.

Note: There are two types of model that we can create in Blender to use as our Physics model :

1. Planes (triangle) type physics model.
2. Box (hull) type physics model.

Planes type is when we construct our physics model using quads and triangles (planes) as you are doing now with the physics model for your building.

Box type is when we construct our collision model using "box" shapes. See below for an example of a Box type physics model for one of your circular rooms.

 

In the Mesh uploader > Physics tab, when using a Planes type physics model we don't touch anything in Step 2 or Step 3 , the mesh uploader leaves our physics model just as we created it. That is a mesh constructed of Triangles. Our collision surfaces will be Triangles.

When we give the mesh uploader a Box type physics model to use for collisions we need to ask the uploader to Analyze it in Step 2 of the Physics tab. The uploader is then tasked to convert the model we gave it into a collection of Hulls ("boxes") We left a little space between each of our boxes when constructing our physics mesh in Blender so that the uploader can more easily create ""hulls" where we want them to be. When Analyzed the collision surfaces will be a collection of Hulls.

But don't worry about the Box type, for buildings its usually best to do as you have been doing, using the Planes type physics. And all you need to remember is when using the Planes type Physics  DON'T  touch anything in Step 2 or Step 3 of the Physics tab of the mesh uploader.

 

 

A quick recap of the 3 rules that should be followed when creating a physics mesh.

1.  Each visual model (object) has to have its own physics model.
2.  The Bounding Box (BB)  X, Y and Z dimensions of the physics model should match the BB dimensions of the visual model.
3.  Keep the physics model as simple as possible.

 

Your physics model is falling foul of rule N° 3,  The mesh uploader doesn't like to find very small, very thin  or degenerate triangles in the physics mesh.

The "very small, very thin" are relative to the size of the model.  What is classed as a 'too small' triangle in a large mesh would not necessarily be a problem in a smaller physics model.

A Degenerate triangle is a triangle with zero area. Two (or 3) of its vertices are occupying the same point in the 3D space.

 

On 2/20/2023 at 9:13 PM, IvyTechEngineer said:

OBWT - pasteall.org has retired, any good options to share Blender files?

 

For short term file sharing you could use Litterbox. https://litterbox.catbox.moe/

Just make sure that you set it to use the 1 or 3 day option.

 

 

 

 

Edited February 22, 2023 by Aquila Kytori

[IvyTechEngineer]

After all my effort it just didn't work. I even did some additional edits in Blender to align the vertical edges between the walkway between the circular buildings. SL is still not happy, lol. I will look closer at the file in Blender. OBTW, attached the existing picture from the SL Viewer.  I thought that if selected 4 vertices that I could use the F to create a new face. I am not sure how to split the faces?

[ChinRey]

1 hour ago, IvyTechEngineer said:

After all my effort it just didn't work.

Two very quick examples. Ideally you want hull (that is analyzed) physcics for a wall but that's a little bit more complicated than surface (unanalyzed) physics for walls as complex as this and I'll try to keep it as simple as possible. For a build like yours it doesn't make that much of a difference anyway.

For a archway/tunnel like this:

You probably want a physics model like this, that is without the small polys along the edge:

Even this is probably too complex a physics model even though it won't cause any upload issues. Something like this would be even better:

 

---

Now for an arched hole in the wall:

Try this:

or this:

or even this:

---

What is important to remember here, is that the only function the physics model for a wall has is to prevent avatar from walking through the wall. Avatar movements aren't very precise so you don't need detailed physics. And you probably don't need the physics model to cover the area above the opening since there's not much chance an avatar will ever end up up there.

Edited February 23, 2023 by ChinRey

[IvyTechEngineer]

I believe I have uncovered part of the error after much trial and error. I must have had some vertices that were very close together. So I selected everything and the merged by distance the vertices and that seemed to fix it. I will probably use the latest physics model for my building. Thanks for your help ...

[Claurice]

Another thing I have found with Blender and uploading Collada from it is, manually triangulate your mesh within blender and disable the option in the upload settings in blender "Triangulate Mesh". I have found that SL triangulates it automatically if it doesn't like the way it was triangulated. This way you can also see if you have any extra verts where they should not be and gives you an idea of where the small triangles are.

Where SL has troubles with buildings is if there are a lot of doors and windows. Also, when you build your physics model be sure to delete any surface on the tops and bottoms of all doors and remove all surfaces inside the windows, so you are only left with inside and outside walls. And all doorways remove the headers as you will not be walking above the door opening lol.

This is how I find the easiest and best way of making buildings and exporting to SL thanks to all the great help from these forums. Your physics model has to be as simple as possible to cut down on LI.

[IvyTechEngineer]

Thanks for the info Claurice, have you found any modifier that can eliminate small tris in Blender? This would be a good addon especially because this is where I got hung up ...

[IvyTechEngineer]

Just a follow-up on this. I just tried to use a medium LOD physics option for a large model and it didn't quite work. In this thread I pretty much decided that I needed a physics file but I still have issues with my models. I just noticed that the physics model I tried to use is being modified in SL where quads are converters to tris? 

[Quarrel Kukulcan]

Judging from how SL didn't triangulate two faces that look like quads, you have some geometry that looks connected but really isn't. Like here.

The thing that looks like a quad on the right really isn't. The lime-colored edge does NOT stop at the vertex in the middle. It's a separate edge that goes directly from end to end. That messes up your surface -- the triangle on the right doesn't share any edges with the two triangles on the left, and there's a zero-width gap between them.

[IvyTechEngineer]

Thanks, I am not sure how that happened. Is there a modifier in Blender to eliminate these problems? 

[IvyTechEngineer]

Final question, which I probably asked before, lol. I have fixed the physics file I think and now I want to texture the mountain. Ideally, I would like it to look like the terrain texture that SL has vs something else. Any suggestions on the least painful way to do that? 

Thanks

IvyTech

[Quarrel Kukulcan]

20 hours ago, IvyTechEngineer said:

Thanks, I am not sure how that happened. Is there a modifier in Blender to eliminate these problems? 

There's no modifier to eliminate them, but there is a built-in plugin that can help find them. Go into Preferences->Add-ons, search for "3D-Print Toolbox" and enable it. You'll get a new tab that you can use to analyze a mesh for geometry errors that'll mess with 3D printing -- most of which will also mess with SL physics. Go into Edit Mode on your mesh and click "Check All" in the 3D-Print tab. Pretty much every error except Sharp Edge and Overhang Face could impact SL physics. If you have any, you can click on the error name to select all the parts of your mesh causing it.

[Wulfie Reanimator]

19 hours ago, IvyTechEngineer said:

Final question, which I probably asked before, lol. I have fixed the physics file I think and now I want to texture the mountain. Ideally, I would like it to look like the terrain texture that SL has vs something else. Any suggestions on the least painful way to do that? 

Thanks

IvyTech

It's not really possible.

The reason why it's not really possible is because SL terrain uses repeating textures that blend between each other (based on height -- like the grass and rock textures in your image).

While you could create a texture for your mesh that blends between two kinds of textures (by doing that manually), the resolution couldn't be anywhere near as sharp as regular SL terrain, because SL terrain uses repeating textures to cover the large surface.

And while you could create your land mesh with repeating textures in mind, your current geometry wouldn't work for it, and you'd lose the ability to blend textures arbitrarily.

Edited March 31, 2023 by Wulfie Reanimator

[IvyTechEngineer]

Thanks for the feedback. So are you telling me that texturing in SL would be better for large objects?

[ChinRey]

10 hours ago, IvyTechEngineer said:

Thanks for the feedback. So are you telling me that texturing in SL would be better for large objects?

Yes and no.

I've done a lot of ground meshes and I've found that 32x32 m is the largest surface a single non-repeating 1024x1024 texture can cover with acceptable resolution and even that is pushing it a bit. For a larger surface you either split it up into several faces (and load the viewer down with a lot of 1024s) or you use a repeating texture. I do both: custom baked textures for areas where the difference really matters and a standard tiled one for the rest of the ground.

[IvyTechEngineer]

Also, I am wondering if I should add some more geometer to improve the texturing of an large object that I upload into SL. The image on the left would be harder to texture with an image? Of course the results are the tri/quad count goes up...

[Frionil Fang]

24 minutes ago, IvyTechEngineer said:

Also, I am wondering if I should add some more geometer to improve the texturing of an large object that I upload into SL. The image on the left would be harder to texture with an image?

The amount of 3D geometry does not define how much texture detail you can fit in, the UV map does. To have more texture detail in a given area, the polygons need to be larger on the UV map, having more of them won't help. Extra geometry could help with distortion, but it depends on the use case if it's worth it. 

Shoddy simplistic example: unwrapping a split plane gets you this:

Subdividing the split part and unwrapping gets you the exact same texture area for the split part, so there's exactly the same texture detail available in those 16 quads as the original undivided one:

To get more texture detail into the split part, you'd need to scale it on the UV map:

[ChinRey]

6 hours ago, IvyTechEngineer said:

The image on the left would be harder to texture with an image?

I don't think it would make much difference if any at all but try both and see. Btw, you do have access to the beta grid so you can do test uploads without paying for them right?

5 hours ago, Frionil Fang said:

Subdividing the split part and unwrapping gets you the exact same texture area for the split part, so there's exactly the same texture detail available in those 16 quads as the original undivided one

That's almost correct but there are no quads in SL, only tris and that can sometimes make a difference. Look at these two cones:

The one to the left has tris going all the way from top to bottom, the one to the right are split in four segments vertically and you can see how that improves the UV mapping. Here they are in wireframe mode:

As I said, I do not think it will make a difference worth mentioning in this particular case but it's worth a try.