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Mesh looks completely different at lower LOD


kennychronic
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Hi there,

I'm uploading the following mesh item and have created low poly versions for different levels of detail. It seems that the Medium and Lowest versions aren't being parsed correctly. Sometimes pieces are stretched way out of proportion, but the current issue is that both pieces of the symmetrical mesh is being mirrored along the X-axis.
If I select the medium detail version as the main mesh, it previews fine. As soon as I choose to use one at a lower LOD, it screws up.

I've had a very similar issue before with a simple mesh whereby a cube was losing edges at lower LODs. Scale and rotation have all been applied. I've recalculated all normals and even tried using the default SL client (I use Firestorm). I've tried the default Collada exporter and Avastar's exporter. All produce the same results.

Sorry, I can't figure out why [img] tags won't work on this board so the screenshots are just links.

Here is the high detail version:
http://i.imgur.com/Tr2XI5B.png

And the lower detail version:
http://i.imgur.com/Oy0PiQQ.png

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I suspect you allowed the mesh upload  to generate the lower LOD's. Thus the problem you have.

I make most of my own lower poly LOD's and especially the lowest poly one. In some cases people will make the low LOD a cube and paste a picture of the hi-rez version on the sides, At the distance where people can see the thing, they can't tell the difference.

Search on re-topologize for infromation on how to reduce poly count without having to model every level.

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You are showing us what the uploader previews.

Have you actually UPLOADED?

 

I have found HUGE diffrences in what the preview window shows and what you see -- both with LODs set at 4 and at 2.

 

If you haven't uploaded on the beta grid, best to do that and see if there is a real prooblem.

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To me it looks like you upload a dae file which contains multiple meshes. In this case the meshes have to appear in the same order in the dae files for each LOD and the physic as well. Or the lower LOD meshes will be assinged to the wrong mesh parts. Like in your case, the left horns is applied to the right horns and vice versa. Because they appear in that order in your medium LoD file.

Easiest way to fix it is merging all the pieces into a single mesh piece.

If that's not an option for you, you have to make sure the export order is correct. How to achieve that depends on your modeling program.

For Blender you can name your meshes alphabetically, and check some checkbox "Keep Order" (or something like that, I don't use Blender myself) in the export section.

In Maya I think you can re-order the meshes in the Outliner.

In 3ds Max they will be exported in the order of their creation in the scene. To re-order them you have to link them to a box, and unlink them in the same order for each LoD export. (Note it's Link/Unlink, not Attach/Dettach)

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I am sure Arton is right. That is also consistent with your description of other cases. The lower LODs of each mesh get stretched or squeezed to fit the bounding box of the high LOD. So if the wrong ones are associated at different LODs, the lower LODs come out distorted as well as moved. In case you are using Blender, here's how you get the naming right: name each mesh with a name shared between LODs, then a postfix for the LOD, as in left_antler_hi, right_antler_hi; left_antler_med, right_antler_med; and so on. Then check the "Sort by Object Name" option in the export settings (this should be automatic in the SL-specific modes).

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Arton, you were absolutely right. I went through my different LOD models and renamed the sub-meshes so there was no disparity. Everything works fine now, and I suspect the same will be for the model I first encountered this issue with too.


Thanks for everyone's responses and suggestions.

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