Problem with physics

[Gordon Nadezda]

I've created a simple building in Blender 2.83. I'm just trying to understand how physics work when uploading the mesh to SL. So far, my efforts have been mostly a failure. 

In Blender, I have the building as one object and the physics as a separate object. The physics object is just above the floor of the main mesh. I've exported the building and physics separately. Before exporting, I've applied all transformations and set origin to geometry for each object. 

In SL's mesh upload UI, I select the Collada file for the building and, on the Physics tab, selected my physics file. I have tried using both the Analyze tool and not using it. 

When I upload the model to SL and rez it in Firefox, I edit the Features tab by selecting Prim instead of Convex Hull. But, as you can see in the screenshots, the physics is way off; my avatar is way above the floor. In Blender, the physics object is not as high up as it shows in SL. 

Below are screenshots of the model (the main mesh and the physics mesh) and how it looks in SL after uploading:

I know this is very simple. But, what could I be doing wrong that's making the physics so much higher than the floor?

[ChinRey]

4 hours ago, Gordon Nadezda said:

I know this is very simple. But, what could I be doing wrong that's making the physics so much higher than the floor?

Did you make sure the visual and physics models are exactly the same size? The uploader will scale the physics (and all LoD models) to the same size as the main visual model so if tehya ren't to start with, you can get unexpected results like this.

Edited June 26, 2020 by ChinRey

[KT Kingsley]

As ChinRey suggests, it looks like your physics model is a simple 2D plane, while the building has height. Try adding a vertical plane, perhaps corresponding to one of the walls of the main model, to the physics model.

[Gordon Nadezda]

1 hour ago, ChinRey said:

Did y9u make sure the visual and physics models are exactly the same size? The uploader will scale the physics (and all LoD models) to the same size as the main visual model so if tehya ren't to start with, you can get unexpected results like this.

You were right. The plane in the physic model had to be exactly the same size. I also added a few vertical planes for the walls. They also had to be the same size. Thanks for everyone's advice.