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Physics Issue


BenjilaBonj
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Hello, i've encountered an issue which I can't seem to get my head around.

When importing objects into SL, I've been importing mesh with a physics shape too, which is analysed and imported. When the mesh is set to 'prim' the physics works perfectly. However when objects are linked together and set to prim, sometimes it doesn't work. Which is fine, so I then go and unlink the objects to their individual parts, set them each back to prim to apply the physics shape only to find that they now will not apply the map at all. Leaving objects being completely phantom. I cannot get my head around how to get the physics shape to apply again.

Incidentally, I'm also having an issue where if I duplicate a mesh object, for example something i'm using as a floor. The duplicated object doesn't have any physics applied to it either, despite whether it's in PRIM or Convex hull.

Is there anything I can do? 

Edited by BenjilaBonj
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2 hours ago, BenjilaBonj said:

Hello, i've encountered an issue which I can't seem to get my head around.

When importing objects into SL, I've been importing mesh with a physics shape too, which is analysed and imported. When the mesh is set to 'prim' the physics works perfectly. However when objects are linked together and set to prim, sometimes it doesn't work. Which is fine, so I then go and unlink the objects to their individual parts, set them each back to prim to apply the physics shape only to find that they now will not apply the map at all. Leaving objects being completely phantom. I cannot get my head around how to get the physics shape to apply again.

Incidentally, I'm also having an issue where if I duplicate a mesh object, for example something i'm using as a floor. The duplicated object doesn't have any physics applied to it either, despite whether it's in PRIM or Convex hull.

Is there anything I can do? 

You haven't pasted any screenshots of what you are doing so difficult to tell. I cannot remember ANYONE posting this issue before. That doesn't mean it is new or just you but I have been watching this forum for many years :D.  It sounds like your physics models aren't correct. 

 

You analyze your model when you are using CUBES (or other simple shapes) as your home made physics model. Those various shapes should NOT touch each other.  You also need to apply location, rotation and scale to BOTH the main model and the physics model. "I" always move the origin to the geometry also.   Linking objects should not change their physics models. So my conclusion is that there is something incorrect with how you are making the models.  

 

Even a very complex item will work using this method.

 

image.png.79f8f66e587078900dc668d93ca67969.png

 

Here is a video on house physics which might help you spot your problem.   

 

 

Edited by Chic Aeon
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2 hours ago, Wulfie Reanimator said:

I'm not sure about the missing physics issue, but don't analyze it if you're using a custom physics mesh because that will create a new and different physics shape, which might have holes or something in it.

If your object breaks down well into solids, set it to "Solid" mode, do an "analyze", and look in the upload window to see what you got. Use Firestorm; it has a resizable upload window, and you'll need to make it bigger.  In that window,  you'll see different colored solid objects, and you can space them apart with the slider.  You want to see nice solid objects. You can try "simplify" if you have too many little pieces.  Solid mode does a decomposition into convex hulled objects, which, put together, add up to the original object.

The convex decomposer (from Havok) isn't very good. That's why the advice to break up things like houses into pieces with a gap between sections. That forces the convex decomposer to break the physics model apart where you wanted. Otherwise, you tend to get a model broken up at rather dumb points. If you see long skinny wedges in your physics model, you may need to fuss with that.

"Surface" mode generates poorer physics models. There's no inside/outside for a surface physics model - it's just a flat surface. So getting caught inside is more likely. The physics engine works better on "solid" models.

At the object level, "prim" mode means "use the model for each prim in the linkset".  "Convex hull" mode means "make one convex hull around the entire linkset."

What's happening isn't all that complicated but the documentation is terrible and the interface is confusing. Once you realize that a physics model is always either a collection of convex hulls or some flat surfaces, it gets clearer.

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