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Complex physic shape with little server load?


Drop Woodland
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Hello.

My use case: Have a project idea that would benefit of a detailed llCastArray() friendly surface. Which i think is a physic shape, but the down side is un-necessary load on the server as it can be complex or many small ones that will add up, when its only purpose is to be invisible and an be an recipient surface llCastArray().

So my question is: Can a physic shape be made server friendly in the sense of a medium/high vertex count ?

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5 minutes ago, Drop Woodland said:

Not be able to measure is a plus in my book : )

I think you misunderstood Coffee there, physics load is very closely monitored and controlled by the software, it's just about the only part of the weights/land impact system that really works well.

I don't think we should be too afraid of physics load though, as long as we are sensible about it that is.

I happen to be working on a mesh ground for Keswick right now so I think I can show you an example (sorry about the texturing and the dodgy prim water, this is vey much a work in prgoress):

image.png.a7de08ea9c2209a1c4af0c78452b9abb.png

This covers pretty much the whole sim. There are some holes for the few parcels I don't own and also for houses that need basement and for various underground installations but these holes don't reduce the physics weight, they increase it.The ground is as detailed as it needs to be (combinedtriangle count for the 24 meshes is 2678) and the physics follows the visual model exactly. Total physics weight for the ground is 114.8.

 

4 minutes ago, Drop Woodland said:

I would like to miniaturize a regions ground topology, each meter which I think is roughly 65536 point. 

Do you mean a full scale model of the ground or a scaled down one? At full scale you'll end up with about 6000 LI worth of download weight so physics cost isn't your only concern there. If you scale it down, you'll still end up with a very high download weight unless you totally butcher the LoD model and even if we ignore the physics weight issue, there is no real point because SL physics and ray casting isn't that precise anyway.

Here's a stack of four prim cubes:

image.png.faa763298f26bb3a0ea337117f0f06a9.png

And here's how Mesh Studio's weird and hardly ever used ray casting scan option sees it:

image.png.23f1e1369043e5906ce60a4985cd9620.png

I'm sure you can get a better result with a perfectly vertical ray cast down onto every single vertice but that seems rather pointless and there will still be significant deviations.

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9 hours ago, ChinRey said:

even if we ignore the physics weight issue, there is no real point because SL physics and ray casting isn't that precise anyway.

This isn't true. SL's ray casting is just as precise as it's supposed to be. I have no idea what Mesh Studio is doing but it looks like they just construct their own data poorly.

You can create fully functional ray tracers with LSL. If you were to script a raycast visualizer (to see how a single ray behaves), you would see that it has practically infinite resolution and doesn't care whether the object is convex or not.

However. Here's 8K tris (24K verts):

85e68dc345.png

Using this for highest LOD only (for visual representation) and physics shape, it's going to take up 49 LI at 1x1x0.5 because of the physics weight.

However, if I enable the rendering of physics shapes, this is the object at 29x29x113 and 191 LI:

0c4911ff79.png

It's just a cone. The sim optimizes it down to a more sane physics shape because it's not big enough for the amount of detail the actual shape demands. In fact, even at 64x64x64 the actual shape won't be used. If the goal is to use a physics shape with 65K verts (points), I don't think that's even possible.

Edited by Wulfie Reanimator
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