Physics problem

[Tealthantos]

So I've put together some modular normal mapped streets, however when I go to upload a shape for the physics all I seem to get is a closed hole across the top of the mesh even though the shape shows ok when I go to upload, (interestingly enough the physics on the underside appear to conform to the shape of the model) anyone have a clue what might be causing this?

 

 

[Drongle McMahon]

How are you uploading the physics shape? Analyzed (convex hull decomposition) or not (triangles)? Then, when you have rezzed it, have you set the physics shape type to "Prim"? (can have concave surfaces) or left it as "Convex hull" (can't have concave surfaces)? Is its bounding box the same as that of the high LOD mesh? Have you looked at the physics shape using menu item Develop->Render Metadata->Physics shapes? A picture of that would help. It it's triangle-based, it will show the triangulation edges. If it's comvex hull(s), it won't. If it's triangle-base, but any dimension of its bounding box is less than 0.5m, it will behave as if its shape is set to convex hull, although it won't appear to be. There is a secret switch on the server that the viewer doesn't know about! It's to avoid shapes with thin triangles, which are the enemy of the physics engine.

 

[Charles Hera]

OK. I just had the exact same thing happen with a roof. Sides were fine but I fell through the roof. I had done Solid, Analyze and set to prim. I had applied Location, Rotation and Scale to both model and physics model. When I looked at the physics it was missing one side of the flat roof part of the physics.  I went back in and looked at the physics dae and I had at least one normal flipped (maybe two as there was an edge that was sticking out the side when it shouldn't have been).  .

 

I just uploaded the same roof DAE with the new Physics DAE and all worked great. You could actually see that there was an issue with the extra physics sticking out in the upload window. I can never see the preview as well in LL viewer as in FS though.

 

It now works perfectly. I had never had a physics cube flip normals before, but good to know what to watch out for.

Rereading the original post, this might not be the exact same thing, but something to check anyway.

 

[Tealthantos]

Unfortuantly neither of the above seem to be solutions, I've tried to increase the thickness of the box but regardless of all options I try, the shape constantly set itself to a box and all normals are correct.

 

It appears I'll have to abandon the project and write it up as another loss to the SL shocking mesh upload system

[Domsson Lean]

Wow, you're giving up fast on this one.

Why don't you try and supply Drongle with a bit more info? He's like a mesh physics magician so chances are he might be able to help with more input.

[Codewarrior Congrejo]

As Domson already said:
if you do not provide a bit more information and also maybe screenshots of the actual physics model etc it is hard to help you.

The SL mesh upload system is actually not shocking. it might have its little quirks and some bugs, but generally you can make things work when you know how they work.

 

Giving up so easily without even really trying is a big nono =) so if you feel like giving it a second try just drop more info and more screenies and i am sure there will be a solution found.

[Tealthantos]

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Domsson Lean wrote:

Wow, you're giving up fast on this one.

Why don't you try and supply Drongle with a bit more info? He's like a mesh physics magician so chances are he might be able to help with more input.

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Not really, its been 4 days since I've tried to get the model on to SL only to be hit with the normal 6 veiwer crashes + 8 mesh upload premission bugs a day until I've just about thrown my keyboard in frustration through my screen and thats even before I even get to deal with the mesh - I just don't have the time in the real world to go through drama -every- -single- -time- on what should be very basic minor projects. (to give you a example, I've tried to get on just before work now as I'm writing this to get you the screens but SL beta has crashed twice, SL normal is refusing to render mesh at all and firestorm might make it - but I've only got 10 minutes before I need to go - and it only even seems to happen whenever I need to try and do something).

 

Anyway I've managed to get on with firestorm - this is what they look like.

[Drongle McMahon]

I cant see anything wrong with those. They look like they are "Analysed". One possible problem - the avatar doesn't actually touch the surface of a prim it walks on. Mine hovers about 0.075m above it. So if that is your kerb height, then maybe that's what's giving the impression that the shape is not concave. They way to get round that is to make the surface of your physics shape a bit lower than the visible road surface to compensate. Then when you stand hovering above the physics shape you appear to be touching the road. The bounding boxes still have to match up, so the visible mesh has to extend down to the bottom of the physics shape, (e.g. with an extra triangle).

Here is a physics shape I tried to check there wasn't a new bug. It's six simple boxes, shown by colours. They are all in the same mesh and are just not overlapping. Uploaded with the LOD mesh in the physics tab after clicking "Analyze".  I could walk on the depressd road surface as expected. Since it is not triangle-based, it works even if the mesh (visible+physics) is less than 0.5m thick.

Since you describe connection problems, I wonder bif your connection could be flaky. The physics is all done on the server - so a poor connection could lead to all sorts of physics errors, which might include not setting the av height correctly.

ETA - I here because the page-blanking problem went away, at least for a while.

 

[Tealthantos]

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Drongle McMahon wrote:

I cant see anything wrong with those. They look like they are "Analysed". One possible problem - the avatar doesn't actually touch the surface of a prim it walks on. Mine hovers about 0.075m above it. So if that is your kerb height, then maybe that's what's giving the impression that the shape is not concave. They way to get round that is to make the surface of your physics shape a bit lower than the visible road surface to compensate. Then when you stand hovering above the physics shape you appear to be touching the road. The bounding boxes still have to match up, so the visible mesh has to extend down to the bottom of the physics shape, (e.g. with an extra triangle).

Here is a physics shape I tried to check there wasn't a new bug. It's six simple boxes, shown by colours. They are all in the same mesh and are just not overlapping. Uploaded with the LOD mesh in the physics tab after clicking "Analyze".  I could walk on the depressd road surface as expected. Since it is not triangle-based, it works even if the mesh (visible+physics) is less than 0.5m thick.

Since you describe connection problems, I wonder bif your connection could be flaky. The physics is all done on the server - so a poor connection could lead to all sorts of physics errors, which might include not setting the av height correctly.

ETA - I here because the page-blanking problem went away, at least for a while.

 

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Thats not it either, if you this pic where I adjusted the middle lower, I still get the same result, which is that I'm standing about .5m above the ground, also this is a new poly cube I've put together instead of the plane I used last time and the results are still the same - its filling in that middle area for some reason and there seems to be no reason for it.

 

Anyway, this is becoming a real waste of time and a money sink - I just don't get what the problem is

[Tealthantos]

but to add to this and its just happend now, I switched the shape to prim and it switched to the shell it was meant to be, which should be impossible

[Drongle McMahon]

I don't understand this. You do have to switch the shape type to "Prim". Leaving it as "Convex hull" tells the server to use the default convex hull of the whole physics shap, which would fill in the depression of the road. But the physics shape pictures you showed did have the depression - meaning they must have been type "Prim". No? Maybe the shape display isn't working properly. Here it is for my simple thing - using physics shape for visible too...

Top is the visual mesh, then the default convex hull you get when it's set to shape type "Convex hull". (Note that this doesn't quite fill the bounding box. I reported that as a bug, but I guess it's intended for some unknown reason.) The convex hull fills up the road space, as expected. So you don't sink into the roadway depression. Both the models below have the same default convex hull when the shape type is "Prim".

Next is the physics shape uploaded using "Analyze", and set to shape type "Prim". It's a set of six convex hulls corresponding to the six separated parts. The roadway depression is now clear, and you can walk on it.

At the bottom is the same model, but not using "Analyze". That results in is a triangle-based shape, as shown by the appearance of the triangles. This also lets you sink into the roadway depression. (The triangle-based shape isn't recommended for this model because the small triangles along the kerbs and the edges of the roadway cause a high physics weight.)

Notes - pictures taken with water, surface patch and sky turned off (Advanced->Render types menu) fot clarity.

[Tealthantos]

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Drongle McMahon wrote:

I don't understand this. You do have to switch the shape type to "Prim". Leaving it as "Convex hull" tells the server to use the default convex hull of the whole physics shap, which would fill in the depression of the road. But the physics shape pictures you showed did have the depression - meaning they must have been type "Prim". No? Maybe the shape display isn't working properly. Here it is for my simple thing - using physics shape for visible too...

Top is the visual mesh, then the default convex hull you get when it's set to shape type "Convex hull". (Note that this doesn't quite fill the bounding box. I reported that as a bug, but I guess it's intended for some unknown reason.) The convex hull fills up the road space, as expected. So you don't sink into the roadway depression. Both the models below have the same default convex hull when the shape type is "Prim".

Next is the physics shape uploaded using "Analyze", and set to shape type "Prim". It's a set of six convex hulls corresponding to the six separated parts. The roadway depression is now clear, and you can walk on it.

At the bottom is the same model, but not using "Analyze". That results in is a triangle-based shape, as shown by the appearance of the triangles. This also lets you sink into the roadway depression. (The triangle-based shape isn't recommended for this model because the small triangles along the kerbs and the edges of the roadway cause a high physics weight.)

Notes - pictures taken with water, surface patch and sky turned off (Advanced->Render types menu) fot clarity.

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No, I skipped part of the sentence in a "lack of caffeine" haze, What I wanted to say was that it added 15 LI to the model when I did so from a fresh upload.

 

So I've gone back and done the mesh from scratch from a cube instead of a extruded plane, on re-upload the hull checked out correctly with a 3 LI.

 

Conclusion? I still don't know what the problem with the original model is, but I suspect the problem was the base polygon.