Design notes

Associated data / ECS

So far, the different structures for representing everything associated with a road/intersection/etc strongly resembles ECS. Would explicitly using an ECS library help?

http://www.gameprogrammingpatterns.com/component.html

Road has different representations:

protobuf
runtime map_model (mostly focusing on the graph)
UI wrapper + geometry for simulation (should probably tease this apart)
"control" layer for editable policies
Queue of cars on the road

It could be useful to bundle together a context-like object of Map, GeomMap, ControlMap, DrawMap, etc.

Need to figure out how to handle reaping old IDs for transient objects like cars, but also things like modified roads. Slot maps?

Immediate mode GUI

Things organically wound up implementing this pattern. ui.rs is meant to just be the glue between all the plugins and things, but color logic particularly is leaking badly into there right now.

Strawman driving model

Show the FSM
Explain how the model is based on best-case bounds
Position is derived lazily from time
How accurate could it be? Based on inner-city speeds and timesteps
problems
- straw model has some quirks with queueing
  - after the lead vehicle starts the turn, the queue behind it magically warps to the front of the road
  - the first vehicle in the turn jumps to a strange position based on the front/back rendering
- at signals, cars doing the same turn wont start it until the last car finishes it

Stop sign editor

Stop signs are FIFO, except that many intersections only have a stop sign for some sides. Going straight on the priority roads is immedite, and left turns from those priority roads also take precedence over the low-priority roads. So should the stop sign controller mark individual turns as priority/not, or individual roads, with implied semantics for left turns? There are really 3 priorities if turns are considered...

Figuring out nonconflicting roads seems tricky. For now, going to have a complicated UI and let individual turns be classified into 3 priority classes. First group can't conflict, second and third groups can conflict and are FIFO. Will probably have to revisit this later.

Sim state equality and f64's

Currently using si::Second for time, which means comparing sim state by deriving Eq is a headache. Since the timestep size is fixed anyway, this should just become ticks. Was tempted to use usize, but arch dependence is weird, and with a 0.1s timestep, 2^32 - 1 ticks is about 13.5 years, which is quite a long timescale for a traffic simulation. :) So, let's switch to u32.

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