Lower poly model getting resized to match higher model and it gets distorted and clips in the process

[Katrina Kungler]

First of all, hey. Secondly. sorry if I explain this poorly.

Instead of letting SLs uploader create the ugly shrapnel low poly models for me, I'm trying to create my own. The problem being, since I've removed polys and the dimensions on both aren't exact (technically they can't be without distortion of the lower one, right? And it would be pretty finicky to get it exact. How would I even go about that?), the uploader is re-sizing and distorting the lower poly model to have the same dimensions as the higher one. The scale for both has been applied and the origin is the same. This wouldn't matter so much if it weren't that I have an overlay layer that I want to sit nicely on top still without clipping. However it's clipping horribly in SL even though it looks fine in Blender.

Aside from making an outer box around the entire mesh and making it transparent so that both have the exact same dimensions, is there any other way to make this work? How do other people do this? I've tried all sorts of searching around for an answer and haven't come up with much so any help is appreciated!

[Beq Janus]

Models have to share the same bounding box. they will get stretched to match. Same applies to physics as well. To fix this you need to place a single triangle at the extent of the BB where there is no other mesh to pad to the correct size. It can be a pain in the posterior but for now it is all you can do.

[ChinRey]

38 minutes ago, Katrina Kungler said:

Aside from making an outer box around the entire mesh and making it transparent so that both have the exact same dimensions, is there any other way to make this work?

To illustrate what Beq said, here's one I made earlier.

Fairly simple tree trunks with two branches:

Top ortho view:

Ideally I'd only keep the trunk (reduced down to nine tris) for the lowest model but that would change the size of the bounding box so I kept one triangle for each branch:

It's still only 11 tris so no big deal.

[Bitsy Buccaneer]

Before I start reductions, I make a mental note of what in the mesh is defining the edges of the bounding box. If the geometry isn't basic enough that measurements will suffice, then as I proceed with the reductions I make sure to keep at least a tri/vertex on each of those edges. What's done with the edge-defining tris/vertices depends on the piece. But the key is using the starting geometry rather than trying to figure out where to put something new.

[Beq Janus]

As both @Bitsy Buccaneer and @ChinRey have noted, the process of determining a "nice" LOD is dictated by the object you are working with. One of the common failings observable when people use auto generated LODS, is the loss of "silhouette". Where possible a good lower LOD loses the details and keeps as much of the shape and volume of the original as it can, this way switches become more transparent to the user.

[Katrina Kungler]

6 hours ago, Bitsy Buccaneer said:

Before I start reductions, I make a mental note of what in the mesh is defining the edges of the bounding box. If the geometry isn't basic enough that measurements will suffice, then as I proceed with the reductions I make sure to keep at least a tri/vertex on each of those edges. What's done with the edge-defining tris/vertices depends on the piece. But the key is using the starting geometry rather than trying to figure out where to put something new.

All of the replies have been helpful but this here made me realize what it is I needed to do to make both dimensions match. Was as simple as looking for the polys that extend furthest and matching those as best as I could to the high poly model and then copying the dimension values so it was exact. Needed a little more wiggling after that but then it was perfect.

Thank you everyone! Was much less painful than I was anticipating. :P

[Chic Aeon]

7 minutes ago, Katrina Kungler said:

All of the replies have been helpful but this here made me realize what it is I needed to do to make both dimensions match. Was as simple as looking for the polys that extend furthest and matching those as best as I could to the high poly model and then copying the dimension values so it was exact. Needed a little more wiggling after that but then it was perfect.

Thank you everyone! Was much less painful than I was anticipating.

Glad you figured that out. Since we really don't see this question coming up often your final thoughts were my original ones LOL. But, that seemed way too simplistic so I just kept quiet. Sometimes is really IS best to understand from the inside out.  

 

Logically if you "take away what isn't really needed" on a model to make a lower LOD, then that solves much of the issue as what you have left is often  the exterior shape of the item. 

 

 I hope it all works out well for you. 

[Bitsy Buccaneer]

1 hour ago, Katrina Kungler said:

All of the replies have been helpful but this here made me realize what it is I needed to do to make both dimensions match. Was as simple as looking for the polys that extend furthest and matching those as best as I could to the high poly model and then copying the dimension values so it was exact. Needed a little more wiggling after that but then it was perfect.

Thank you everyone! Was much less painful than I was anticipating.

I'm so pleased to hear this ❤️

My other trick is to save and export frequently while I'm removing bits in Blender, with the number of tris included in each name. When I go to the beta grid to test, I try different combinations in the uploader to see how it affects LI and upload the most promising. Then I zoom in and out on different graphics settings to get a feel for how the LoDs shift. If the initial upload(s) do unsightly things, or could just be better, I have a pile of other daes ready to try instead. (And if I have to back track to try a different route, I have a range of very useful mid-point files to start from.)

This works better for me than trying to plan ahead for the middle two, and anything which makes this process less stressful is a big plus . I'm just saving and exporting as I work my way down to the lowest. This approach has also taught me a lot as it makes it simple to experiment, looking for a good balance between efficiency, detail, and preserving visual continuity. Sometimes bits which I think matter turn out not to and can be safely gotten rid of, or doing something slightly differently makes the LoD sequence flow much more smoothly. Important to remember to keep track of which files I've used, so my beta grid tests will generally include strings of numbers (the tri counts) in their object names. When I decide a final combination, those go in one subfolder labeled "Used" and the rest in "Unused" as it does get messy otherwise 😬

For all I know this might be common practice and I've just never heard anyone else mention it. Or maybe they all have better ways. All that matters in the end though is that you find a workflow which suits you.

Good luck with your mesh. It can be unbelievably frustrating, but it's also very rewarding.