Issue with collision in mesh

[Naiman Broome]

Hello I uploaded several models but just now I realized that the collisions do not work as showed in the preview ...

 

why? why the collision ingame looks like a big shape block and instead mine is more precise one , accepted and upload is instead messed up like that?

 

I have 4 linked objects as mesh and 3 have null collision one is set to full collision and is the trunk ...

 

thanks for any answer ...

 

[Nalates Urriah]

I can't tell if you made a physics layer or let the viewer make one.

The trunk looks too complicated for the physics engine. I would have made the collision layer from 2 to possibly 4 cubes or triangles. The curved trunk if used for physics would drive the LI too high.

If you allowed the viewer/physics engine to build the physics layer, it will be had to know what you are going to get when it actually uploads.

I'm not that good with physics layers, so hopefully someone else will add more.

[Naiman Broome]

Seems I just had to put the physic to prim rather than convex hull ...

this seems to work .

[Drongle McMahon]

In the picture you show, it looks as if you have made a physics mesh (as you have selected from file). It isn't clear whether you are going to upload this without clicking "Analyse" or after clicking it. If you don't "Analyze" you will have a triangle-based physics shape. This shoulf work, but with the small triangles for the trunk in your physics mesh, it might have a high physics weight, which might lead to high LI. If you do "Analyze", you will get a hull-based shape - the uploader will make a set of convex hulls approximating your shape. Looking at your mesh, this might be expensive too. If you are going to use a hull-based shape, the most effective way to get a good shape is to use a model that is already a collection of non-overlapping convex hulls. That gives you the closes control. If you have to start using the Analyze parameters inatead, it becomes difficult to avoid the filling in of parts where you don't want it.

The picture of the physics shape display is no very clear because of the thing in the background, but I think it may be revealing why your collision shape isn't what you expected. Whatever you do on the physics tab in the uploader (including doing nothing), the uploader always makes a default convex hull for the whole (of each) mesh object. This is what you get if you leave the physics shape type set to "Convex Hull". It is NOT the same as the shape generated by "Analyze". It has all the concave spaces filled in. It's not what you want here.

To use either triangle-based or Analysed, hull-based shapes, you have to set the type to "Prim". Whether it's triangle or hull based then depends on what you did in the uploader. You can't switch between those after upload. The shape you show for the trunk looks like the default convex hull. So my guess is that it is set to type "Convex hull" when it needs to be "Prim". Over-use of the Analyze simplification parameters could have a similar effect. I can tell it's not a triangle-based shape because those show the edges of the tringles in physics shape view. So if you didn't Analyze, then it's certain that you have the type set to Convex hull.

For your tree trunk, my physics shape would be something like this, using Analyze to make a hull-based shape. This is four simple non-overlapping (gaos exaggerated) boxes, each a convex hull. After Analyze, this ahould give 4 hulls and 32 vertice, and the uploader will report that at the bottom. That should give a physics weight of 1.44, which won't increase the LI above 1.

ETA: I see I was too slow, as you found the answer already. :matte-motes-frown: