The Right Physics

[Rosanna Ewing]

i made a build with 3 floors in blender and i have try to make own physics for it. When i uploaded it to SL and set it to prim everything is fine - except the 3 floors: when i'm standing on the floor my feets go through it!

So my question is: what is the right method in my own made physics for the 3 floors in the mesh build? It's a mesh cube build really simple 3 loops for the floors and each one flat face. Do i need in my physic cube for each floors a plane above and below?? What i want to note: ii don't prefer the normal prim solution.

Quick help would be nice thx in andvance :-)

[Pamela Galli]

Mesh less than .5 m thick will act like Convex Hull. 

[ChinRey]

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Rosanna Ewing wrote:

What i want to note: ii don't prefer the normal prim solution.

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Just one comment first: the prim solution is not the "normal" one, it's an emergency fix for mesh makers who don't know how to make mesh for SL.

 

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Rosanna Ewing wrote:

So my question is: what is the right method in my own made physics for the 3 floors in the mesh build?

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If the floors are separate meshes, the easy way out is to make their physics models from cubes and use analyzed physics. Use as few cubes as possible for each floor and if a floor needs more than one, make sure there's a slight gap between them. This is not an ideal solution since you don't really want to use anayzed physics for walkable surfaces but it's fairly easy to do and the disadvantages are usually trivial enough to be ignored. It is possible to use unanalyzed mesh for individual floors - there are several workarounds to the 0.5 m limit Pamela mentioned - but that's when it gets a bit complicated.

If the floors are parts of a larger mesh, well normally that's not a good solution but it is a quite common one and at least it allows us to use unanalyzed physics:

• Make sure the floor surfaces are positioned at exactly the same position on the physics model as on the main visual model.
• Make sure the overall dimensions of the visual and physics models are identical. If they are not, the uplaoder will resize the physics model and that can lead to all kind of unexpected results.
• Make sure the normals for the floor surfaces are pointing upwards. Unanalyzed physics is directional so this is crucial.
• Because of the directional nature of unanalyzed physics you probably want to include physics for the ceiings too, not just the floors but that shuoldn't affect the walkability of the floors.
• Make sure there are no smooth normals in the physics model.

 

[Rosanna Ewing]

Thx ChinRey for your quick response.

First i want to mention that i mean with "normal prim solution" not that this is the "normal" solution i only mean with "normal prim" the in-world-prims often named as  "normal prims" and i have heard that also "experienced" mesh makers work from time to time with these prims in combination with their mesh creations.

Indeed the floors a part of a larger mesh build so i will pay attention to your points thx :-)

[ChinRey]

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Rosanna Ewing wrote:

and i have heard that also "experienced" mesh makers work from time to time with these prims in combination with their mesh creations.

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Not experienced ones, no. But even the most experienced ones may have had to do it before they became experienced and later decided it wasn't important enough a problem to be worth the time and effort fixing. You can often link a lot of prims to a mesh without increasing the land impact so although it's not something you're likely to do once you udnerstand how mesh physics work, it's usually not big enough a deal to worry much about either.

[Chic Aeon]

There was a time when mesh was new that physics wasn't working -- well it wasn't working well.  You would fall throught the end of a thick cube floor even with a physics model. Back then, the somewhat obvious solution was to mix prims with mesh. I did that four years ago as the strange things we had to go to to let folks walk on floors was less than fun AND while it worked for awhile, "someone" changed things and then it no longer worked.

 

Happily physics has been much improved since then. 

One thing you might find easier would be to import your model in sections -- each with a physics model. That way you can test as you go along. You can of course upload the whole thing as a giant linkset with corresponding physics models but that does get trickier. 

 

There is also something to say for "modular" buildings as they can often be reused in part or modified for other uses. 

Be sure and test that you can rez an object on your floor to see if you have the physics correct *wink*. That pesky rezzing in the middle of the air OR outside (OMG I have one of those -- not mine thank goodness) is a pain. 

 

Good luck. 

[Pamela Galli]

Tip: Stretch an invisible prim over the entire floor, very slightly above the floor surface. Or just under. 

[Chic Aeon]

LOL. The point of the OP was "correct physics" not "cheating". I don't have issues any longer; a correct physics model solves that. As written in my comment ---- that was four years ago .  And if you were really righting to the OP, I think they knew that work around already *wink*.

[Pamela Galli]

People mention that annoyance often, how they have to drag things outside etc., and the tip is an obvious one but some have not thought of it yet  :-) 

[Rosanna Ewing]

Thx Chic for your comments. As you described i did my build years before with mixed prims because of the problems especially with the floors. I wanted to rebuild it and find a "correct", elegant and prim save solution concerning the physics. And i find it interesting to hear your experiences and tips :-)