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MissBegotten

I'm working on my first build (a house) and need to pick some brains.

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I'm building in world with prims. My plan is to export my build when finished and make it a mesh before uploading it again.  But, having never done this before, I don't know how to prepair for it.

 

I know how to export as a collada.  Then I have to play with it in blender a little before uploading it.  What exactly is saved when I export?  If my build has things inside will they be lost if the outside is a box without any holes?  Maybe I should export the roof as another file and put the two parts together after uploading them?

 

Also will I be able to texture the item after I upload it or must I texture  before uploading?

 

Thanks for helping!

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I am sure there are others that can give you a much better answer to this but my suggestion is build some very simple structures, just a few prims and texture them and then download them and upload to the beta grid (free).

Try different viewers, I don't think there is a standard method for downloading as mesh.

Make very sure that every texture you use was uploaded by you, otherwise it won't download.

Find out/experiment with the Physics Shape Type setting in the edit box on the Features tab.

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Hi :)

So i'm guessing the goal of this Project is to end up with a building with a lower LI than one if it had been made with prims.This would mean reducing the triangle count in Blender as much as possible and having walls etc that are texturable + having correct Physics. Thats quite a big ask for someone who is only just starting out. Let me try to walk you through a very "simple" example, a cube and point out some things to look out for and to do further research on.

I created a cube in SL , resized it , rotated it about the Z axis and then gave each face of the cube a colour. Using the Singularity viewer I exported it to my hardrive and opened it in Blender. Before I forget let me mention that Singularity's .dae exporter has a couple of Options worth mentioning. Consolidate Faces, "Export faces that have the same texture as one." and Skip transparent faces, any faces that are made 100% transparent will not be exported as part of the mesh.

First thing to note is in Object mode we can see that the  6 coloured faces have been imported along with the cube and second is that the scale is 2 in all axis and the rotation in the Z axis is 180°.Cube Object mode.png

Not having the rotations set to zero and scales not set to 1 can cause problems later on so lets fix this first :

1: In Object mode with the cube selected use the short cut keys Ctrl + A to open the Apply menu and choose Rotation and scale.

Next  have a look at the imported cube in Edit mode.

Cube Edit mode.png

First thing to note is the Vertice/Triangle count 96/108 . a basic cube only needs 8 vertices and 12 triangles so these have to be reduced.

Second we see that the cube is devided into triangles, its better they are changed to Quads while working in Blender. (The Quads will be automatically converted back to Triangles when the mesh is exported to the Collada .dae format for uploading back into SL)

Third the cube is made up from separate faces, the edges of the cube are not joined to each other.

And Fourth the UV mapping of the cube has been exported along with the mesh when converting to .dae in Singularity. In the UVmap all 6 faces have been stacked on top of each other, which is correct for the SL cube. UV's are very important, each vertice of the mesh in 3D space is mapped to a point in 2D space (UV map) so that each pixel of  a texture using this same UV space can be mapped back to the correct point on the surface of the 3D mesh. Its a must to understand what UV's are and the different ways of producing them inside of Blender. Google Google Google.

So lets get started on reducing those vertices:

2 3 4 .png

2: Just shows the cube asit is when brought into Blender.

In edit mode and all the vertices selected:

3: To convert the Triangles to Quads,     Ctrl + F   to open the Face menu and choose Tris to Quads. Doing this makes it alot easier to select edge loops later on.

4: To get all the edges joined together we can use the Remove Doubles option. This will join together into one vertice any vertices that are occupying the same place in 3D space.  Ctrl + V to open the Vertices menu and choose Remove Doubles.

5 6 7  .png

5a: and 5b: All vertices that are not contributing to the shape of the mesh can be deleted. To do that select all the vertices that are not the corners of the cube and delete them. With those vertices selected use the X key to open the Delete menu and choose Edge Loops.

The cube is now optimized and if you look at the UV's you will notice they are still intact. Which means the when the cube has been uploaded into SL it will still take taextures as before.

ready to export to SL.png

6: Because the cube is so simple a copy of this cube can be used as the Physics/ Collision mesh. In Object mode make a copy of the cube, Shft + D and move it to another layer with the M key. Then in Object mode you can remove all the materials from this Physics cube.

The cube is now ready to be exported back to SL, In Object mode, with the cube selected: Edit > Collada (.dae) and in the Collada export menu check the Selection Only check box. and save.

Repeat for the physics cube.

In the mesh Uploader, load up the cube.dae file in the LOD tab and the Physics cube.dae in Step 1 of the Physics tab

When rezzed inworld edit the cube and in the Features tab change Physics Shape Type from ConvexHull to Prim.

Ok, that may or may not seem like alot of "playing" about in Blender for a simple cube, Try it, then try it with a little open room. With Prims create a floor, 3 walls and a flat roof, give the walls and floors etc their own colours faces and link together and export .......................In Blender, Object mode with all the parts selected,   Ctrl + J  will join them into a single mesh object. You are going to need alot of patience  to Optimize this imported room from the 438 vertices/480 tris to 16verts/28tris.

Producing a physics/ Collision mesh wouldn't be to hard......

BUT And you will probably have to UV unwrap this new mesh room from scratch ! ........ 

Now think about what will be involved in doing this for a whole building !

Plans are made to be changed right ..........you are going to have to learn some Blender basics so why not do the whole thing in Blender ?

You will find a nice series of  Blender tutorials here 

 

BTW have you heard of prim to mesh software? Google or ask in the Builders Brewery Group chat about that. If i remember correctly they even hold classes for at least one of them.

 

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I haven't exported a prim model to Collada in a long while so I don't remember all the details, but if I remember well the exporter lets you export all the objects you have selected.

So, if you have a house made by several parts, all the parts you select will be exported as a coalesced model. All the linked prims will be exported as a single object, thus if your house is made by 2 or 3 linksets the exported model will be made or an equivalent number of objects. I suggest you link as many prims as possible into a number of linksets you are comfortable with. Any prim object that is not selected won't be exported, so unselected things inside your build won't be exported.

Once you import your model into Blender you'll see that there is quite some optimization to do. Prims model have a number of faces that are not required in a well built mesh model.

For texturing, you can do it either way. Texturing with an external tool will give the best results if you know how to do it.

UPDATE: Oops! I see that Aquila just posted a much more extensive and detaiiled answer.

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What's even the point in building with prims if you are going to export and reupload it as mesh. The modifications you'll have to do in blender to optimize your build is as much or even more work then when you would have modelled your build in blender in the first place.

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True.

 

Aquila did a wonderful job of setting forth steps necessary to do what you want, MisBegotten. You're going to have to learn Blender to accomplish it, so it's probably inefficient to start in world with prims because of the extra work you'll have to do in Blender. Just my two cents.

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Building a prim mockup inworld to be exported is actually very useful when you need to build to measure for a building to fit in in an environment, mostly when the terrain is not flat. Trying to build a house on a hill or sloping ground is a hit-or-miss exercise which may lead to far more work. It also helps to get an idea of the scale of the building. There is no need to build the entire model down to the small details, just a simple mockup is enough.

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I think building with prims is good to learn for everyone who wants to build. Even if you plan on making mesh only.

I use inworld prim building for mockups a lot too. I just don't export into blender. I take the measurements and start a clean build in blender, it's a lot faster and cleaner that way...

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I think you should use whatever method you're happy and comfortable with. There's more than one way to skin a cat. :matte-motes-smile:

 

But that being said, I can't really see any practical reason for redoing with Blender prims work I've already done with SL prims. Mesh Studio at least creates wonderfully clean dae files that are excellent starting points for editing in Blender. The only limitations that script has in that respect are those of the prim system.

Then there are textures. There's no doubt that Blender's UV mapping tools are more suitable than SL's for large even surfaces but for smaller details that require irregular "organic" texture mapping, texturing is often far easier in SL than in Blender. In Blender you often have to spend ages moving vertices on the UV map or resort to lag inducing custom textures to get the same lively result you can get with a few little tweaks in SL.

SL texturing can also have an advantage for simplest texture map: a single repeat across a square/rectangluar surface. Blender sometimes has an annoying tendency to shift the vertices slightly away from the corners of the UV map even when we tell it not to. Add the texture as exactly one repeat across a prim face, export with Mesh Studio and that problem is solved.

And finally there's a question of LI and I'm not really sure about this - need to do some tests here...

My builds tend to have significantly lower LI than comparable builds by others. There are many reasons for that but I believe on of them is that most of my builds started off as prims. As I said, I haven't done any scientific tests but after tens of thousands of uploads of files made with various software, I have a very strong impression it si so. It's not impossilbe btw. Drongle has shown several times in this forum how even minor changes in the syntax of a dae file can affect the LI you end up with.

This little example I made for a completely different topic may be interesting here - although hardly conclusive:

https://community.secondlife.com/t5/Mesh/UV-Unwrapping-increase-land-impact-alot/m-p/2879847#M30202

Later in the thread Drongle reproduces my example with models built from scratch in Blender and he ends up with download weights 20-30% higher than what I got.

This is hardly firm enough vidence for a conclusion but it's certainly worth a closer look. I don't have time to do any experiments right now but if anybody else would like a go at it, please do! We would need several tests with different shapes to reach a conclusion, one try woudln't be enough.

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MissBegotten wrote:

Then I have to play with it in blender a little before uploading it.  What exactly is saved when I export?  If my build has things inside will they be lost if the outside is a box without any holes?

I think the best answer is, export, open file in Blender and see what you've got. :matte-motes-smile:


MissBegotten wrote:

Maybe I should export the roof as another file and put the two parts together after uploading them?

Making a complete house as a single mesh is hardly a good solution any way you look at it. If you want the lowest possible LI, you'll need to "balance" the weights, that is make the download weight and server weight roughly similar (the third weight, physics weight, shouldn't be a significant factor for a house in any case). Splitting up a mesh into separate parts will usually reduce download weight but will always increase server weight. Getting the balance right there is one of the most important parts of the art of meshing for SL.

(Edit: speaking of splitting meshes, you do not want to mix small and big tris - say a wall and a window frame - in the same mesh. It can be done effectively but you have to know exactly what you're doing or you'll end up with horrendously high LI or, even worse, poor LOD or - most likely - both.)


MissBegotten wrote:

Also will I be able to texture the item after I upload it or must I texture  before uploading?

Both. The textures you apply before meshing will be lsot but the mapping reain so afterwards all you need to do is drag the textures from your inventory onto the faces of the mesh.

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