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How to reduce prim count on large buildings?


Naiman Broome
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Posted (edited)

Make them smaller. Beyond about 45m object radius you get no LI reducing benefit from medium/low/lowest LOD levels so it's all about how much geometry you have in the highest LOD.

Edited by Candide LeMay
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When it comes to Li, scale is your enemy.

Really big structures will be MUCH cheaper to make from prim if you can.

This can be easier to accomplish for large structures if they are not designed to be habitable / host avatars. Move away from architectural design and towards paper craft / popup book. Think in terms of textured surfaces, creating an illusion of depth with alpha masked layers. By all means create a full model, but use that as an intermediate step to generate image maps.

If your structure needs to host avatars, only build out those specific sections.

Create the build with specific viewing conditions in mind. 

 

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5 hours ago, Naiman Broome said:

Is there any trick or system to redouce Land impact of huge structures imported into SL ?

Yes, there are a lot of tricks but the most important ones in a case like this are to never make a big house as a single mesh and never mix large and small tris in the same mesh.

The walls of a building is usually made from fairly few big tris while details like windows, doorframes etc. are made from a fairly large number of small ones. So keep those separate.

And here's a bonus trick that doesn't affect land impact but has other positive effects: Never upload identical meshes!

If your building has several identical windows (they nearly always have) or pillars or whatever, make and upload a single copy of it and duplicate it in-world. You save a bit of upload fee that way and it also reduces the bandwidth and load time for the building.

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6 hours ago, Coffee Pancake said:

Really big structures will be MUCH cheaper to make from prim if you can.

Just wanted to note that is not necessarily true.  CAN be instead of WILL be would be more appropriate. I'll let others explain, but didn't want that to go without comment.  And there are oh so many things that you can build in mesh that you cannot build in prims.  I "LIKE" prims; they are just not always the answer -- or even "often" these days. 

One trick I will mention (and hardly ever use because I am a minimalist gal) is that you can separate the inside from the outside IF you build is complex AND you want all those details to be made into the mesh (think interior arches and such or some other detailing that is part of the main structure).   You can upload the INSIDE with very different LODs since people will not be seeing those parts from a long distance. Upload the outside separately and make sure your LODs are good for "at least" the folks at LOD2.  

 

TEST TEST TEST and the beta grid is your friend if you can get there (not sure how that is working since our new owners but some things have changed I hear).  

 

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  • 3 weeks later...

Make custom LOD's, they'll look nicer and you can selectively axe the stuff people won't really notice from afar. The example I can think of off the top of my head is like with a car, you probably won't notice the suspension or interior from 50+ meters away, so removing or reducing it significantly in the high to medium transition is probably fine. A good rule of thumb is making each LOD transition about half the verts/faces as the last, and doing a custom one also keeps your pretty model from looking like a bush of triangles.

For large objects you can degrade LOD a lot faster, since it will transition at much farther ranges, a large blimp or so will still show up in high LOD way outside the range that the car will drop in detail. If the object is large enough you /can/ get away with making the LOD drop to minimal after high, because realistically nobody will see that at any reasonable distance away but its one of those things where you really have to give it some thought beforehand.

The advice others gave like using smaller objects or removing unseen faces is also great for dropping LI.

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syzmtowerexterior.thumb.jpg.7a7d233032265c891edaa25f95354d46.jpg

Possibly SL's best large building. Go to NTBI region; you can't miss it.

It's fully detailed inside. Lobby, offices, elevators, escalators, parking garage, mall, restaurant, restrooms, emergency stairs...

 

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One thing not mentioned here is the importance of knowing how to get the best out of your physics mesh

If the physics mesh is one complicated mesh that is all joined together, the physics weight of the object skyrockets and in turn the LI.

You can still have fairly accurate physics on a building, but the trick is to make a physics mesh out of many separate mesh cubes (with no vertices joined to other cubes). Has something to do with how the havok engine does things.

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