General

Dimensions

The unit used for object dimensions is meters.

Coordinate systems

The local coordinate system is a right-handed coordinate system according to ISO 8855 with the axes pointing to the directions mentioned below. For a non-rotated coordinate system, the following applies:

  • Forward matches x-axis

  • Left matches y-axis

  • Up matches z-axis

TODO: Add images similar to OpenDRIVE? See https://publications.pages.asam.net/standards/ASAM_OpenDRIVE/ASAM_OpenDRIVE_Specification/latest/specification/08_coordinate_systems/08_04_local_coordinate_system.html

The coordinate system is in line with the standards ASAM OpenDRIVE, ASAM OpenSCENARIO, and ASAM OSI.

Origins of the coordinate frames for specific object classes are under discussion.

Naming conventions

The following naming conventions apply to ASAM OpenMATERIAL geometry files:

  • The name of a 3D model file shall have the prefix omg_ to indicate that the file complies with the ASAM OpenMATERIAL geometry specification.

  • The 3D model file and the related 3D asset file shall have the same base name.

Putting more information in file name to be discussed for specific object classes.

3D asset file

The 3D asset file provides meta data as well as a mapping table to ASAM OpenMATERIAL material property files. This information extends the geometry of an asset given in standard 3D model file formats, e.g. glTF, FBX or USD. The 3D asset file is in JSON format with the file extension xoma. As indicated above, the asset file has to have the same file name as the accompanying 3D model with the prefix omg indicating, that the 3D model file is structured according to the ASAM OpenMATERIAL geometry specification. This is an example of a 3D model file in glTF format with an accompanying 3D asset file:

  • omg_my-model.glTF

  • omg_my-model.xoma

Each 3D asset file contains the following information:

  • Metadata

  • Material mapping (with possibility to easily change assignment)

  • Optional link to another asset file to facilitate instancing (same asset file for different 3D models)

  • Semantic information (labels) for sub-meshes ?

  • Description of coordinates, pivot points and so on instead of hierarchy in 3D model file ?

  • Assigning data streams (for example, wheel rotation) to certain sub-meshes ?

TODO: Add short descriptions and references

Requirements

Materials shall be separated.

TODO: Extend rule and find better location. What do you want to express, that two materials with different properties need to be modeled by separate objects? Are there any other requirements regarding quality, semantic/animation/material structure?

Recommendations

  • The same texel density should be used within a file. (asset file?)

  • For each object class, the recommended mesh resolution should be used.

  • To improve performance of vegetation objects, alpha textures should be used.

TODO: Move recommendations to descriptive sections, e.g. object class recommendation to section "Object Class".