Mesh Origin issue - offset to ground

[Morris Venenbaum]

Hello,

 

I have created three objects (that I upload at one in SL), and set the origin in Blender to 0,0,0.

After uploading in SL the mesh rezzes above ground.
And it keeps the the same offset even if I try to rezz it on a prim (to sort out that it was caused by a mesh floor).
Even more interesting is the fact, that the offset to the ground scales with object size (small object=small offset, large object=large offset).

 

Any ideas?

[Drongle McMahon]

Do you mean you exported three Blender objects in a single collada file, without joining them, getting a linkset of three objects in SL? Or did you make/join them into one Blender object? In either case, how did you make the physics shape(s)? Did you look at the physics shape (Develop->Render Metadata->Physics Shapes)? Can you show us a picture?

One thing to note - the origin in Blender is not relevant. A new origin is effectively placed at the geometric center of the xyz-aligned bounding box of any object's geometry. This is part of the method used to maximise geometric precision within the limitations of the 16-bit internal vertex data format. After that is done for the high LOD, all the other LODs and the physics shape are stretched or squeezed to fit the same bounding box, one object at a time.

[Morris Venenbaum]

Thanks for your response. It is greatly appreciated.

 

To answer your questions:

I exported three objects into one collada file without joining them.
This creates three linked objects.

 

Regarding the physics shapes:
I assume you refer to the tab in the SL import window?
I have not considered it at all. Maybe that is already causing the problem?

The activation of the Metadata Physic Shapes shows... nothing. Except of that some surrounding objects (the skybox that is) turn blue.
What is this menu about?

 

[Drongle McMahon]

I assume you refer to the tab in the SL import window?

Yes. If you did nothing with it, then your three objects should each have the default physics shape. That is, for each separately, the "convex hull" of the low-LOD version of the visual mesh. I don't think this would extend below the visible mesh. In that case, I can't right now see how it could account for the whole thing floating. However, as long as it is a linkset, then it could be that only one of the three objects rests on the ground.

Metadata Physic Shapes ... What is this menu about?

(In LL viewer) It's supposed to show you the physics shapes. They are usually light blue, but go through beige, orange, red as the physics weights become excessive. For triangle based shapes you can see all the internal edges. For hull-based shapes, you just see solid blue (etc). Sometimes you will see objects with just an outline of the bounding box, no blue. I'm not sure what that is meant to be, but it happens at least with some invalid physics shapes, or sometimes when the server decides for some unknown reason. Mesh with None physics shape type are also just barely visible ghosts.

 

[Reven Rosca]

I suppose your origin is at Blender's center <0,0,0> ?

The only way you can accomplish this and keep this origin after import to SL is to add an extra face below the visible mesh, so that the point you want to be your origin is in the center. 

A mesh will rez with it's lower bounding box side level with the floor or ground where you rez it. the distance from the ground vil vary depending on size just as you describe.