Restructure points and segments

[TheDuckCow]

Right now, we have RoadPoints as children of a points node which needs to be added as a spatial to the scene.

However, there are new oddities introduced if the player then tries to move/rotate/etc the "points". Furthermore, this points node would have to remain as a Spatial if RoadPoints are to be parented to it, otherwise we can't get the benefit of chained parent-child transform chaining.

The proposal, which is not backwards compatible:

• Make it so that all RoadPoints need to be direct children of their corresponding RoadNetwork
• Remove the need for the points node.
• We could furthermore make the segments node hidden int he editor, and strictly always placed as a direct child (removing the option for users to move this around as they please). RoadSegments would still be parented to this node, and it still needs to be a spatial for show/hide to work correctly.

[TheDuckCow]

Update to this task: We are going to go down this route described below, as it will better serve many details later. Instead of the initial proposal above which keeps a Segments spatial, everything will be hierarchical to RoadPoints instead.

So the idea is that in a formed scene, you might have a structure like this:

• RoadNetwork
  • RoadPoint A
    • RoadSegment
      • Generated geometry, collision mesh, etc
    • RoadLanes (connecting RoadPoint A to B)
    • Additional curves to represent the outside edges of the road, for dynamic content placement (to account for lane changes etc)
  • RoadPoint B
    • RoadSegment
      • Generated geometry, collision mesh, etc
    • RoadLanes (connecting RoadPoint B to C)
  • RoadPoint C
    • Disconnected, so no children
  • Intersection Scene [nested pre-formed scene]

Some rationales for this structure:

• Each RoadPoint is only responsible for its "next" roadpoint
• This way, we could even add preview visualizations (where if you select a roadpoint, it auto-shows LaneSegments in the editor, as a convenience to imply the section you have selected)
• By correlating a RoadPoint and a RoadSegment, you then will have a way to access the segment to add additional elements to, like railings or sidewalks.
• Also each RoadPoint greedy-generates the RoadSegment between itself and other roadpoints (greedy in that it'll try to generate it, unless it's already been generated before)
  • It's an option that we switch now to deterministic generation: a roadpoint is only responsible for generating it's own (though its neighboring RoadPoint could politely ask it to self generate, for the same "greedy" effect)
• This paves the way to supporting custom road mesh scenes, so users can bring their own model. Prefab scenes to build roads are what a lot of users expect, and so being able to have RoadPoints in their own subscene is an important step to be able to do that.
• Open issue: Right now RoadPoints don't care about directionality, so they can face either way and generate segments all the same. But now, the direction matters.
  • Two RoadPoints who both list each other as the "next" one: We'll have to pick one of them, probably the higher one in the scene hierarchy. Likely they'll both have the same outcome.
  • Tow RoadPoitns facing away from each other, both listed as the "prior" for each other: This is the bigger problem, as nothing is taking ownership of that middle roadpoint. We'll have to think of some solutions, but one example could be to insert another roadpoint that overlaps and points one way to own the generation. This way, there can be arbitrary flips through the road without consequence or need to "normalize" directions, which could undo scene artist work.
• Intersections are a broader point, but this just shows how they'll fit in above, as nested scenes that have their own structure. Everything else above is directly a node (but not all will be made visible in the editor immediately, since they could be re-generated).

I'll update this task as I refine it further, but it is the first major work to take on to get this all working.

[TheDuckCow]

This task is in progress, and arguably done.. however the result has exasperated underlying issues that have to do how geo is transformed from local to global space.

Due to RoadSegments now being children of RoadPoints, which are themselves rotated by the user, we have cascading transforms to inverse and undo. I made an initial quick fix that seemed to undo rotation and was evidently working well, but upon further review I found that connecting road segments with non-xz flat orientations created weird twisting that was not present before. Additionally, when it comes to intersections and prefab scenes, we know it will be important to be able to rotate and translate entire road networks without consequences. Right now translation is fine, but rotation has long been a no-go (in fact, the very original version of the RoadNetwork class actually had it as a base Node object, not a spatial, to try and prevent any transformations).

So, instead of continuing to build on a stack of cards, I'm rolling up my sleeves and trying to get my head around the particular points of issues. What I've come up with is the following areas needing fixing

1. Where we calculate the normal used to extrude geometry from a single loop within the middle of a road segment generation (need to fix this first! Cascading effects otherwise)
2. Where we se the handle in-out points of the RoadSegment's curve
   • (simplified for now by zeroing them out, always straight lines now, zero magnitude)
3. Where we calculate the last loop within a road to ensure things are connected
   • (simplified for now by not generating that loop, to avoid further confusion)

These changes are all going into the 74-restructure-points-and-segments because I don't want to merge this branch if it creates new quirks that weren't present before. Stay tuned as I wrap my head around the right sequence of xform and xform_inv's...

[TheDuckCow]

The good news is this branch is just about ready finally! I was able to resolve the last of the consistency issues yesterday. However with some QA playing around with it today, there's one annoyance now with the new structure:

When you select a roadpoint, you see a bounding box around the road segment contained within it. While in one way this is actually nice as it clearly indicates which roadpoint owns that segment of road, it's rather distracting especially as you rotate or move the roadpoint around (since the box continually is resizing). It would be nice to have control over how we visualize the owned roadsegment by disabling this selection box outline.