Model Building

[IvyTechEngineer]

On 10/14/2020 at 6:10 PM, Aquila Kytori said:

To get a download cost of 90 using a similar object to yours  ( proximately 2000 triangles ), the model had to be 40 x 40 x 40m !

 

 

If your model is not this size then something else is going on.

Can you upload your .blend file to this Blender file sharing site so that we can check it out and do our own test uploads?

https://pasteall.org/blend/

 

For reference: When dimensions set to 1 x 1 x 1m,  the mesh set to Smooth Shading,  UV's zeroed and using default upload settings the result is :

 

When read your initial post I skipped over the "UV's zeroed". Is this done in SL or Blender? Thanks

[arton Rotaru]

23 hours ago, IvyTechEngineer said:

When read your initial post I skipped over the "UV's zeroed". Is this done in SL or Blender? Thanks

I guess Aquila meant that she just hasn't done a proper UV mapping on this test mesh, to get the UVs out of the equation. Since UVs will have an impact on the download weight. You certainly need to properly unwrap your mesh to be able to apply a meaningful texture to it.

[Aquila Kytori]

22 hours ago, IvyTechEngineer said:

When read your initial post I skipped over the "UV's zeroed". Is this done in SL or Blender? Thanks

This is done in Blender but it is not something you would normally do on a model.  Zeroing out the UV's means selecting all the UV islands and scaling them down to zero so that all the vertices on the UV map are mapped to a single point in the UV space. Normally not a very useful thing to do.

So why did I do that and then mention it in my post ?

This was about Land Impact right and I said:

" For reference: When dimensions set to 1 x 1 x 1m,  the mesh set to Smooth Shading,  UV's zeroed and using default upload settings the result is : "

• Size.
• Shading.
• UV's

Amongst other things those 3 things effect the LI (Download) cost of the model.

So that you or anyone else following along could get the same (or very similar) results they would have to have a model the same size using Smooth shading and have the same UV unwrap (mapping).

Zeroing out the UV's like that ensures that you or anyone else would be using the same UV layout as in my example. 

 

In the following images notice how the Triangle count in the mesh uploader remains the same but the Vertex count changes depending on the UV layout.

The first image shows the vertex count when uploading the model which had the UV's Reset then scaled to zero and then positioned at the lower left hand corner of the UV space:

 

The next is the same model which has had had seams added along the hard edges of the 1/4 spheres and along the middle of the central sphere:

 

Model UV unwrapped using the Smart UV Project method :

 

and the same Smart UV project unwrap followed by scaling the UV's to zero:

 

Note: It is OK to have the UV's scaled to zero if you are just going to apply a single color to each material face when you have it rezzed inworld.

It is also sometimes used in Low poly texturing. See this video at 2:11, the section on Colorizing low poly objects :

https://www.youtube.com/watch?v=1jHUY3qoBu8

 

[ChinRey]

2 hours ago, arton Rotaru said:

Since UVs will have an impact on the download weight.

The UV mapping can actually have a slight impact on the download weight. It can be worth keeping in mind when the weight is close to something-point-five and you want it to be rounded down rather than up.

Since this old thread has resurfaced, I think I should remind of something I said in my first reply. This specific build is a very clear example of "Mesh for Mesh' sake". It would have been much more efficient as prims.

[Coffee Pancake]

17 hours ago, Aquila Kytori said:

The next is the same model which has had had seams added along the hard edges of the 1/4 spheres and along the middle of the central sphere:

 

As an aside.

Models do not always need to have a unique texture space for every face. identical UV islands can be perfectly overlapped to share the same final texture. It can be a bit fiddly to work out in blender so bakes aren't destructive in ways you don't want (as areas will be rendered over the top of each other doing this).

In the case of this fancy cube - the top and bottom will need there own space, the visible 2 sides could share with the rear 2 sides.

Also not all faces need be equal in the amount of texture space they get. interior parts could be much smaller.

As an aside to an aside ... if textures are being rendered in blender and object orientation isn't going to be fixed, lightmap packing can be very efficient. This does however make manually editing textures later in 2D paint program impossible.

17 hours ago, Aquila Kytori said:

Note: It is OK to have the UV's scaled to zero if you are just going to apply a single color to each material face when you have it rezzed inworld.

There are special effect purposes for doing this (like making neon, scrolling colors, or emulating nearest neighbor texture filtering with geometry), but in general it's to be avoided. SL's renderer can get glitchy if specular /shiny is applied to faces with zero'd UVs. Especially as shiny is used in SL as shorthand for "I didn't make a texture for this".

[IvyTechEngineer]

I wanted to talk about another model. This one was developed in Maya by another person shared with me for Second Life. It is an obj file. I imported it into Blender with no problems. It is a very small model - triangles = 54, faces = 27, edges = 58 and, vertices = 32. There is also an image (texture) that came with the model as well. I recented it in Blender and just did an export as a dae file. 

Here is the Blender file https://pasteall.org/blend/c6191221dda340e2a82ac00cdc303bf3

and the image file.The finished file looks great in Blender and even in Second Life. The final model - Upload fee - L$ 11, Land impact 0.500, Download 0.064 Physics 0.360 and Server 0.500. The only thing I was uphappy with was the Lowest LoD. Any suggestions of how to make this look better without too much of a negative impact? 

 

[ChinRey]

2 hours ago, IvyTechEngineer said:

Land impact 0.500, Download 0.064 Physics 0.360 and Server 0.500. The only thing I was uphappy with was the Lowest LoD. Any suggestions of how to make this look better without too much of a negative impact?

You can probably use model above for all LoD level and still keep it at 1 LI.

If that doesn't work, remove a few of the tris for the lowest LoD model only. You should be able to get that LoD model down to less than 20 with no visible deterioration and that should be more than enough to keep it at 1 LI.

[arton Rotaru]

For more complex meshes it's often best to create a second texture just for the Lowest LOD. In 3ds Max I project the texture of the hi LOD onto an imposter model. In this case this would be just a bottomless cube. With leaving some room for the imposter UVs in the original UV layout it's even possible to have those 2 textures just as one, which is preferable indeed.

[Aquila Kytori]

Chinrey has already explained that all you need to do is use the high LoD model in the High, Medium and Low LoD slots then create a Lowest LoD model by making a copy of the High LoD and removing as many faces as you can being carefull to keep the remaining mapped to the texture.

And now arton has suggested other methods,

1: Using a bottom less cube for the Lowest LoD model, creating a new much smaller texture and map the cubes faces to  it. 

or

2: Rework the original texture to leave space for the faces of the bottom less cube. This would also mean a little editing of the original High LoD's UV's.

Example :

Texture modified (in Gimp) to add ( cut and paste) small imposter images that will be mapped to the faces of the cube :

 

Cube for Lowest LoD model, UV unwrapped and the faces mapped to the little imposter images that were added to the modified image texture :

 

Example Blend file with packed image texture :  https://pasteall.org/blend/3235adc051d6450dacc39d722fe52314

 

In the SL mesh uploader :

Load up the High LoD model as usual.

For the Medium and Low LoD slots use the Use LoD Above option.

Load up the Cube in the Lowest LoD slot.

For Physics, in Step 1: you can use the Lowest LoD model option, and Analyze in Step 2.

 

Note that you can save image textures in the .blend file by checking the  File > External Data > Automatically pack Into Blend option before saving.

Edited October 1, 2021 by Aquila Kytori

[IvyTechEngineer]

Thanks to all of you for answering my questions. I appreciate it...

[IvyTechEngineer]

Several of you have suggested in the past that models could be built in SL. I would like to build some simple roof truss structures in SL and I assume the SL Viewer is probably not the best to use? I have not used Firestorm but I believe it might have more features?  Anyone have a good links to videos to show how to create structures? 

Thanks

ivytechengineer

[Mollymews]

4 hours ago, IvyTechEngineer said:

these trusses can be built with inworld prims

using what we call prim torture (cut path)

going left to right, top to bottom of the drawing

1)  3 prims (3 triangles) for 1.5 LI linked

2)  4 prims (4 triangles) for 2 LI linked

3)  2 prims (1 triangle and 1 strut) for 1 LI linked

4)  4 prims (3 triangles and 1 strut) for 2 LI linked

5) 4 prims (3 triangles and 1 strut) for 2 LI linked

6) 5 prims (4 triangles and 1 strut) for 2.5 LI linked

a advantage of buildng these with prims is that the LI cost is the same up to a span of 64 meters. And the prims will hold their visual shapes

experienced mesh makers tho can significantly reduce the LI for the overall structure by making multiple trusses as a single mesh object

we can use any viewer for this kind of inworld prim building. I would suggest tho using a  TPV viewer that can export the prim trusses to a .dae file (the standard Linden viewer doesn't do this).  Then you can load the file into Blender/Maya and play with combining/cleaning them up to be a lower LI mesh model that can then be uploaded to SL

quite a few people have learned Blender/May  this way.  The loaded .dae is visually the same as the inworld prim model

 

Edited November 2, 2021 by Mollymews

[ChinRey]

10 hours ago, IvyTechEngineer said:

Several of you have suggested in the past that models could be built in SL. I would like to build some simple roof truss structures in SL

If you want to make them as illustrations for your classes, this is one of the fields where prims really excel. The method is very similar to how construction is done in RL and you can also build (manually or with a script) while the students are watching so they see the whole process not just the end result.

A friend of mine, DV Signature, is doing something very similar on Kitely, only the topic is health and safety, not structural engineering. Here's a snapshot from his region there (with more Howe trusses than you can shake a stick at):

I strongly suggest you create a Kitely account and visit his region there (it's named Signature Safety LLC) and also try to get in touch with him. I think you have a lot to share with each other.

If you haven't already, you should also attend some of the basic prim building classes at Builders Brewery or HHBS or some of the other inworld building schools.

Anyway, assuming you know nothing about prims (sadly way to common these days), you make them by opening the Create tool (Ctrl+4):

Then click on the ground to make a 0.5x0.5x.05 m cube

Once you have created the prim, you can resize, reposition, rotate and reshape it to your heart's content either by typing values into the number fields or by dragging (hold down the Ctrl key to rotate manually, Ctrl and Shift to resize manually):

For beams like this, always use the Z axis for its length.

The by far most useful prim twist function for such projects is the Slice. Set the beginning or end value to 0.5 to cut away half the beam so you have the pivot point and nominal center at one of the ends rather than at the physical center of the beam:

Remember to tick the "Stretch Both Sides" checkbox if you resize manually after slicing.

Then of course, combine several beams to make the model:

I probably shouldn't have gone for a Fink truss with such a high pitch but this was just a quickie and you get the idea.

There are of course a lot of tricks and techniques to speed up the process but describing them all is a bit too much for a forum post.

Edited November 2, 2021 by ChinRey

[IvyTechEngineer]

13 hours ago, Mollymews said:

these trusses can be built with inworld prims

using what we call prim torture (cut path)

going left to right, top to bottom of the drawing

1)  3 prims (3 triangles) for 1.5 LI linked

2)  4 prims (4 triangles) for 2 LI linked

3)  2 prims (1 triangle and 1 strut) for 1 LI linked

4)  4 prims (3 triangles and 1 strut) for 2 LI linked

5) 4 prims (3 triangles and 1 strut) for 2 LI linked

6) 5 prims (4 triangles and 1 strut) for 2.5 LI linked

a advantage of buildng these with prims is that the LI cost is the same up to a span of 64 meters. And the prims will hold their visual shapes

experienced mesh makers tho can significantly reduce the LI for the overall structure by making multiple trusses as a single mesh object

we can use any viewer for this kind of inworld prim building. I would suggest tho using a  TPV viewer that can export the prim trusses to a .dae file (the standard Linden viewer doesn't do this).  Then you can load the file into Blender/Maya and play with combining/cleaning them up to be a lower LI mesh model that can then be uploaded to SL

quite a few people have learned Blender/May  this way.  The loaded .dae is visually the same as the inworld prim model

 

Thanks, I have Blender and Maya on my work PC but want to use Blender if possible. So the workflow would be to

1.) Create truss inworld using a viewer like Firestorm

2.) Export as a DAE file and modify in Blender and reupload file. 

I have not totally mastered the use of Blender but it seems to have excellent support, is free and I have used it to convert STL files to DAE files in the past. I typically draw CAD files using a program called Solidworks and then attempt to reduce the mesh using various techniques in Blender. 

[Quarrel Kukulcan]

1 hour ago, IvyTechEngineer said:

1.) Create truss inworld using a viewer like Firestorm

2.) Export as a DAE file and modify in Blender and reupload file.

If the goal is to generate an illustrative, example structure in-world for other residents to log in and look at, the workflow is

1) Create truss inworld

 

There's no reason to export and re-import unless your main goal is to create a Blender model, in which case modeling the truss in Blender is faster and easier anyway.

[IvyTechEngineer]

4 hours ago, ChinRey said:

If you want to make them as illustrations for your classes, this is one of the fields where prims really excel. The method is very similar to how construction is done in RL and you can also build (manually or with a script) while the students are watching so they see the whole process not just the end result.

A friend of mine, DV Signature, is doing something very similar on Kitely, only the topic is health and safety, not structural engineering. Here's a snapshot from his region there (with more Howe trusses than you can shake a stick at):

I strongly suggest you create a Kitely account and visit his region there (it's named Signature Safety LLC) and also try to get in touch with him. I think you have a lot to share with each other.

If you haven't already, you should also attend some of the basic prim building classes at Builders Brewery or HHBS or some of the other inworld building schools.

Anyway, assuming you know nothing about prims (sadly way to common these days), you make them by opening the Create tool (Ctrl+4):

Then click on the ground to make a 0.5x0.5x.05 m cube

Once you have created the prim, you can resize, reposition, rotate and reshape it to your heart's content either by typing values into the number fields or by dragging (hold down the Ctrl key to rotate manually, Ctrl and Shift to resize manually):

For beams like this, always use the Z axis for its length.

The by far most useful prim twist function for such projects is the Slice. Set the beginning or end value to 0.5 to cut away half the beam so you have the pivot point and nominal center at one of the ends rather than at the physical center of the beam:

Remember to tick the "Stretch Both Sides" checkbox if you resize manually after slicing.

Then of course, combine several beams to make the model:

I probably shouldn't have gone for a Fink truss with such a high pitch but this was just a quickie and you get the idea.

There are of course a lot of tricks and techniques to speed up the process but describing them all is a bit too much for a forum post.

Thanks for your feedback ChinRey. I have created a few things inworld using the SL Viewer. My objective is to 1.) build the roof trusses myself or 2.) have the students build them. All my engineering classes use CAD programs like Solidworks or AutoCAD. I have then been saving the files as STL files and importing them into Blender to reduce the mesh size. This has sort of worked but others have suggested just building objects IW and I thought I would try it for these trusses. Creation of objects using prim inworld seem awkward vs using a CAD program.  

I signed up for Kitely and will reach out to your friend once I can figure out how to login with Firestorm, lol

[ChinRey]

3 hours ago, IvyTechEngineer said:

Creation of objects using prim inworld seem awkward vs using a CAD program.

That depends on what kind of object. For ones that are made from simple euclidian shapes like those trusses, I'd say SL's prim system is the easiest options - once you're familiar with the most important tools of course. It's a different story for more complex and/or organic shapes though.

 

3 hours ago, IvyTechEngineer said:

I signed up for Kitely and will reach out to your friend once I can figure out how to login with Firestorm, lol

You need the opensim version of Firestorm. Apart from that logging in is just like SL.

[ChinRey]

18 hours ago, IvyTechEngineer said:

Creation of objects using prim inworld seem awkward vs using a CAD program.

A second reply to this since I got curious and had to do a test.

Here's a 5:12 pitch Howe roof truss made in-world with prims. Eight prims, 4 LI. It took me six minutes to make - or 5:58 to be exact - including the time I spent calculating angles and lengths.

 

I tried to mesh it too:

• Exporting with Firestorm and cleaning up in Blender: 3 minutes
• Creating LoD and physics models: 4 minutes (or 6-7 minutes to do it properly I didn't really reduce LoD models as much I I could and should, I stopped once I had it down to 1 LI)

All new tools are awkward at first of course and if you're already comfortable with a method that'll do the job, it may not be worth the effort to learn a new skillset. But prims have a very gentle learning curve compared to any other 3D modelling system/software I am aware of.

[IvyTechEngineer]

ok, I am attempting to draw beams in SL with angle cuts on each end. Consider a beam that is 4.7 meters long as measured on along the outside edge of the beam. How would I cut both ends. One cut is at a 25 degree angle relative to the horizontal plane and the other end is 65 degrees relative to the top beam edge and the vertical axis. 

Suggestions?

Thanks

ivytechengineer

[ChinRey]

21 hours ago, IvyTechEngineer said:

One cut is at a 25 degree angle relative to the horizontal plane and the other end is 65 degrees relative to the top beam edge and the vertical axis.

Oh. Well yes, that's where it gets a little bit tricky. I would actually still have made the structure with prims but if I needed details like that, I would export to Blender and fix it with the knife tool there.

There is one workaround though, let to beams overlap like this (I've made one beam a bit darker to show it better):

You might want to make one of them a little bit narrower than the other, like this although not nearly as exaggerated:

 

[Mollymews]

On 11/9/2021 at 2:32 PM, IvyTechEngineer said:

ok, I am attempting to draw beams in SL with angle cuts on each end. Consider a beam that is 4.7 meters long as measured on along the outside edge of the beam. How would I cut both ends. One cut is at a 25 degree angle relative to the horizontal plane and the other end is 65 degrees relative to the top beam edge and the vertical axis. 

Suggestions?

Thanks

ivytechengineer

experiment with

Path Cut:  B = 0.25  E = 0.39  (about)

Hollow: = 80.0 (about)

Size: X = 2.5 Y = 7.0  (about)

these give you (about) something to see how it can be done

the main thing is to get the Size ratio and Path Cut: E to line up when Path Cut: B = 0.25

 

[IvyTechEngineer]

On 11/9/2021 at 6:06 PM, ChinRey said:

Oh. Well yes, that's where it gets a little bit tricky. I would actually still have made the structure with prims but if I needed details like that, I would export to Blender and fix it with the knife tool there.

There is one workaround though, let to beams overlap like this (I've made one beam a bit darker to show it better):

You might want to make one of them a little bit narrower than the other, like this although not nearly as exaggerated:

 

ok, I understand. I was thinking that maybe overlapping elements was the way to do it. Just trying to be as accurate as I can with the drawings. OBTW, is there a way to hid the avatar when you are drawing? Also, I was thinking about adding a ground grid or layout template on the program. Maybe this would make things easier.  

[IvyTechEngineer]

On 11/10/2021 at 3:40 AM, Mollymews said:

experiment with

Path Cut:  B = 0.25  E = 0.39  (about)

Hollow: = 80.0 (about)

Size: X = 2.5 Y = 7.0  (about)

these give you (about) something to see how it can be done

the main thing is to get the Size ratio and Path Cut: E to line up when Path Cut: B = 0.25

 

wow, I would never had figured that out. I will give it a try. Thank you Mollymews. 

[ChinRey]

27 minutes ago, IvyTechEngineer said:

OBTW, is there a way to hid the avatar when you are drawing?

You can always use Ctrl+Shift+Alt+4 to hide and show avatars but I think most builders simply cam away from their avatar.

Camera control is a rather important skill for builders btw. So:

• To focus on and object: Click on it while holding down the Ctrl and Alt keys.
• To shift camera sideways or up and down, hold down Ctrl, Alt and Shift and use arrow keys or move the mouse
• To rotate camera, hold down Ctrl, and Alt and use arrow keys or move the mouse
• To cam in and out, either use the mouse wheel or old down Alt and use arrow keys or move the mouse
• To revert to default camera position, hit the Escape key

One of the requirements to become a real SL builder is to fall off your work platform without noticing because you and your camera are too focused on your build.

 

40 minutes ago, IvyTechEngineer said:

Also, I was thinking about adding a ground grid or layout template on the program.

There are several free builder grid textures available. Carl Metropolitan's is probably the most common and you can pick it up at MP: https://marketplace.secondlife.com/p/Basic-Builders-Grid-Texture/8534776 or here: https://marketplace.secondlife.com/p/Basic-Builders-Grid-Decimeter-Scaled/8667959

Or maybe you want to make your own. Metropolitan's grids only cover a 10x10 msurface since that was the size limit back when he made it. I used to solve that limitation with texture repeats but maybe it's time to come u with a new 64x64 m one?

 

 

[IvyTechEngineer]

On 11/15/2021 at 5:16 PM, ChinRey said:

You can always use Ctrl+Shift+Alt+4 to hide and show avatars but I think most builders simply cam away from their avatar.

Camera control is a rather important skill for builders btw. So:

• To focus on and object: Click on it while holding down the Ctrl and Alt keys.
• To shift camera sideways or up and down, hold down Ctrl, Alt and Shift and use arrow keys or move the mouse
• To rotate camera, hold down Ctrl, and Alt and use arrow keys or move the mouse
• To cam in and out, either use the mouse wheel or old down Alt and use arrow keys or move the mouse
• To revert to default camera position, hit the Escape key

One of the requirements to become a real SL builder is to fall off your work platform without noticing because you and your camera are too focused on your build.

 

There are several free builder grid textures available. Carl Metropolitan's is probably the most common and you can pick it up at MP: https://marketplace.secondlife.com/p/Basic-Builders-Grid-Texture/8534776 or here: https://marketplace.secondlife.com/p/Basic-Builders-Grid-Decimeter-Scaled/8667959

Or maybe you want to make your own. Metropolitan's grids only cover a 10x10 msurface since that was the size limit back when he made it. I used to solve that limitation with texture repeats but maybe it's time to come u with a new 64x64 m one?

 

 

Thank you this was very helpful. I like the grids.