Mesh objects not swapping LODs at the same distance.

[arisaie]

9 objects uploaded as 1.

I have been trying to optimise my mesh LODs for the lowest LI but running into a problem where 4 (2 mirrored) objects Med>LOW  LOD swap distance is 49m, while the other 5 objects have Med>Low LOD swap distance 77.6 - 78.2m.

This is kind of breaking the LOD1 impostor swapping in as between 49 and 78 m camera view theres an empty space in between and it doesnt look good.The impostor is part of the 78m Object and is both sided planes with baked material (so it looks like the object from far away but its actually just planes). The 49m object gets  removed in LOD1 and LOD0 and is replaced by the impostor. I have tried leaving triangles at the edges on all sides where the 4 objects  are to keep the object same proportions but that didnt seem to help.

49m seems far enough,  who cares about LODs! /s

Is it something to do with bounding boxes?

The whole object bounding box is <7.522, 1.66, 3.922>. Only importing the part with the "bad" LOD swap gives me a bounding box of <7.340, 1.32, 3.7468>. 

I managed to make it swap correctly once or twice when trying uploads with lowest LI but I have since merged/deleted objects/faces and I cant seem to make it so it swaps at the same distance again.

Thanks.

Edited October 5, 2022 by arisaie

[arton Rotaru]

For non-rigged objects the swapp distances are indeed depending on the bounding box sizes of the individual meshes.

[ChinRey]

As Arton said, you there is no way to get objects with different bounding boxes to swap LOD in sync. Usually this is a feature since it allows us to dial in different swap distances for different parts of a larger build but sometimes, like in your case, it is a problem.

However:

1 hour ago, arisaie said:

I have tried leaving triangles at the edges on all sides where the 4 objects  are to keep the object same proportions but that didnt seem to help.

That should minimize the problem. Are you sure the bounding boxes of all parts are not only the same size but also in exactly the same position?

It won't completely eliminate the problem since there's always a bit of random delay in the LOD switching process but under normal circumstanbces this should hardly be noticeable.

[arisaie]

Turns out I was doing it wrong...

For some reason I was making the LODs fit the bounding box and not the main object mesh and also doing the mirrored objects at once so I actually only had half the bounding box.

This time I made triangles diagonal across each other on X and Y and Z axis for each mirror and now the bounding boxes and LOD swap distance is identical across the objects.

[Quarrel Kukulcan]

5 hours ago, arisaie said:

For some reason I was making the LODs fit the bounding box and not the main object mesh

The lower LODs should fit the main object's bounding box because SL will rescale them to match if they don't, and that can throw your alignment off.

Physics frame too.

[arisaie]

Yep, all fits now! No changing size between LODs.

I had issue with physics shape though. Had to be set to PRIM but sometimes the LI jumped from 10 to 24, the other time the LI actually increased when scaled down and stayed the same when scaled up.

So I fixed it by making a separate object with the physics set to convex hull, joined them, and set the original to NONE. No LI increase so its propably fine.

Edited October 8, 2022 by arisaie