Environment structure: Object grouping and coordinate systems unclear

[LudwigFriedmann]

Describe the bug
Texts and illustrations in documentation chapter 7.3.4 Environment Structure, more precisely

• Grp_Terrain
• Grp_Environment_Objects
• Grp_Buildings
• Grp_Vegetation
• Grp_Road_Network
• Grp_Sidewalks
• Grp_Road_Marks
• Grp_Road_Objects
• Grp_Signals

are potentially misleading.

Text and iluustrations read as the corresponding group nodes describe single objects.
The illustrations even show individual coordinate systems.
However, this is not the case. The group nodes share their origin with Grp_Root, i.e. the reference coordinate system.
We have to decide here whether we are talking about individual objects or overarching groups here.
In the former case, we may have to define coordinate systems.

To Reproduce
Steps to reproduce the behavior:

1. See Documentation 7.3.4 Environment Structure

Expected behavior
We have to decide here whether we are talking about individual objects or overarching groups.
In the former case, we would have to define coordinate systems.
In the second case, we have to adapt the texts and illustrations and state that the objects share the coordinate frame of Grp_Root.

Screenshots

System Information (please complete the following information):

Additional context

[ClemensLinnhoff]

You are right. The Grp Nodes don't have transforms. The images show individual objects within this group that may have their own coordinates. We need to clarify this in the text.

[lyndyRott]

In the original description of the environment objects, a class item was described as a multitude of objects of the same type (or simply plural). This was changed by the linguistic review:
see commit 6a56d53 from November 27th

transformations (T) were removed before this on Nov 22nd

I assume that this is the ambiguity you are referring to?

Maybe someone can make the choice and adjust the description and possibly the transformations if needed, after deciding on a strategy, as I am not familiar with the details.

[LudwigFriedmann]

All right, then we're clearly committed to the group/layer based approach.
I can clarify this with 1-2 sentences per paragraph and will create a corresponding PR.

Before we update the images (i.e. remove the coordinate systems), I'd like to discuss whether an introductory illustration featuring an overlay of all layers would be useful?

[ClemensLinnhoff]

Before we update the images (i.e. remove the coordinate systems),

I don't know if we should remove the individual coordinate frames, as they show that each object in that group can have its own coordinate system. But I also see, that it might be confusing. What do you think about having these coordinate frames in a different color? Or just a lighter shade of blue?

whether an introductory illustration featuring an overlay of all layers would be useful?

Yes, I think this might be useful. We have that for the bones in the human class and it gives quite a good overview.

[LudwigFriedmann]

I think bounding boxes, such as those in illustration for 7.3.4.3.4 Grp_Environment_Objects, would be better.
In my opinion, this would be sufficient to illustrate that we might be dealing with individual objects.