Confused by odd collision shape

[Indigo Mertel]

I am not sure to understand what I am doing wrong with the collision shape of a mesh model I am making. This image shows the model:

 

And here is the collision shape I made for the stairs:

 

 

However, when I check the collision shape of the stairs in Aditi this is what I get:

 

 

Any idea on why the shape is all messed up?

 

[Aquila Kytori]

Hi

Not sure whats wrong with physics your mesh once it has been uploaded (looks like its being stretched) but you could try the following :

1: In Object mode with the Physics mesh selected Apply Rotation and Scale.  ( Ctrl + A )

2: Make sure that if your stairs are a single mesh object then the  physics mesh is also a single mesh object.

3: When exporting the physics mesh make sure that you have Selection Only checked in the Collada export panel.

Ideally your physics mesh should consist of non overlapping convex hulls ( boxes) and be Analyzed in the uploader, or simple planes, and not analyzed. Your physics mesh looks as if its a bit of a hybrid 

Perhaps you may get a clue to whats going on if you try uploading your Physics mesh as the high LOD mesh an see how it looks when rezzed

 

 Edited to add :

An  after thought , maybe you have used a mirror modifier when creating the physics mesh ? If so check to see if has been applied or check the Apply Modifiers box in the Collada export panel.

 

[Sassy Romano]

A simpler but obvious question, did you actually specify your collision object as the object to use for physics in the uploader?  As in this (apologies if this is blindingly obvious and yes, of course you did this) :-

[Chic Aeon]

You already received a great answer .

As a rule I know always apply location, rotation and scale before uploading as well as moving origin to geometry. Simple and it does solve some physics (and other) problems along the way.

The only thing that I see that looks problematic on your physics model is that the top edge of the stairs are at an angle and not separate cubes.  While I am SO not a physics pro I don't think your model needs to be as elegant as Aquila's. .   Her's are always SO pretty. Mine are not. Mine still work - LOL.

What is important is the cube or simple planes idea. The upload will make the adjustments needed for you. You can also SEE in the upload window if there is going to be a problem with the physics shape, so just looking at that panel will let you know.

Good luck. Nice looking stairs. I am wondering what is going to happen with those really thin wire pieces though. Might easily be a viewing problem. Let us know how it works out.

[Drongle McMahon]

Just in case...

Is your model made of several Blender objects? If so, the physics model needs the same number of objects, each being the shape for the corresponding visual mesh, each having the same bounding box as the corresponding visible mesh, and with corresponding meshes in the Collada file in the same order in visual and physics model files (done by appropriate naming and checking "Sort by object name" in the exporter). That's a tall order for something like this staircase, and you would probably be better off joining it as one object, unless there is a special need for separate objects in SL.Then follow Aquila's advice for the physics model.

[Indigo Mertel]

Thanks a lot for the great tips, guys! I think you have nailed the problem and I am going to try what you suggest after this reply. Here are some additional info:

 

• Rotation and scale are already applied. I have noticed before how these can cause problems
• I believe the problem is that the model is made of different objects while the collision shape is a single object. Thanks for pointing this out, I was not aware of it.
• Chic, the model looks really nice inworld. The wires don't cause problems. LI is 11, a tad high but I may be able to reduce it further.

Thanks again, you have been of great help. 

 

 

[Drongle McMahon]

COncerning the LI, if you need to reduce it...

Not sure, as it depends on the exact size, but I suspect the low LOD (rather than the lowest) will be the most important to simplify for low LI. You can probably remove the wires completely at that LOD, and maybe the upright bannisters too. If you want to be sophisticated, you can replace the wires and bannisters with planes (four, to face both ways for each side) with an alpha texture with the wires and bannisters, for the low and lowest LODs. It has to be on its own material, of course. Use a hidden triangle for that material at the higher LODs. That's the way railings were done before mesh, and at the low LOD distance, it should be adequate. This is the same technique used with window frames, fences, etc. It can provide very low LIs with very acceptable appearance. The alpha glitch is unlikely to be a problem at the low LOD distances.

[Indigo Mertel]

Thanks for the tips on LI reduction, Drongle. I have not worked on the lower LODs models yet. Actually, as I have been experimenting with the result on Aditi I have set the lowest and low LOD to 0 in the uploader. I am not even sure about the medium LOD, as the stairs will be in a room so I don't need it to be visible at a great distance. Previously, the uploader estimate was a 46 LI.

[Drongle McMahon]

Oh yes. I should have looked first - more than 12000 triangles. So it won't get very low whatever you do with the LODs.