Solved Confusion with Blender vs RoR axes

[grahamjamesaddis]

I've raised a ticket against the ror_import and ror_export scripts to load truck files into Blender.

Import into Blender switches x and y axes · Issue #2531 · RigsOfRods/rigs-of-rods

Using the Blender importer the X and Y axes are swapped. https://github.com/RigsOfRods/rigs-of-rods/blob/master/tools/blender/ror_import.py The exporter swaps them back so when used together there ...

github.com

It seems the x,y,z axes in Blender don't line up with the RoR axes after importing.

The exporter makes the reverse translation, so the RoR file lines up again, so it's not actually a problem during use.

Some possibilities.
1. It does work correctly and I'm getting very confused (quite likely)
2. There's a good reason for doing it this way.
3. It's wrong and nobody noticed, or cares.

I'd prefer option 1 or 2...

Any thoughts/explanations?

I've added a very simple blend and truck file to the ticket to describe the problem.

 

[4x4convoy]

the blender and ror axis are different. im not sure how the 2.79 importer worked but it accounted for this rotation on import then on export.

 

[grahamjamesaddis]

the blender and ror axis are different. im not sure how the 2.79 importer worked but it accounted for this rotation on import then on export.

That would be option 2 then,

Funny, it seemed the same to me and I couldn't understand why the translation. Any idea where it's documented?

Thanks.

 

[4x4convoy]

in RoR x is front-back, y is up-down, z is side to side
in blender x is side to side, z is up-down, y is front-back

 

[grahamjamesaddis]

in RoR x is front-back, y is up-down, z is side to side

That explains a lot, much appreciated

So, if I get this right, for RoR coordinates:
+X towards the vehicle rear.
-X towards the vehicle front.
+Y towards the vehicle top.
-Y towards the vehicle bottom.
+Z towards the vehicle port.
-Z towards the vehicle starboard.

Correct?

I can't find this described in the RoR documentation anywhere.

Is it convention?

I can understand that the up-down axis needs to be fixed so RoR knows which way up to place a vehicle, but could left-right and front-back work the other way around?