tokyo-wangan-racing/tools/diag_steer4.luau

--[[
	diag_steer4.luau -- isolate the real constraint on steering.

	Prior runs had a CONFOUND: every hoisted/static test commanded exactly
	-MaxSteerAngle, which is exactly the servo's LowerAngle limit. Sitting a
	servo precisely on its own limit can deadlock it. The isolated 2-part
	servo (target -30, limits +/-35) worked perfectly, so the API is fine.

	This matrix commands -20 deg (well INSIDE the +/-35.08 limits) and varies
	one thing at a time.
]]

local ServerScriptService = game:GetService("ServerScriptService")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RunService = game:GetService("RunService")

local out = {}
local function log(...)
	local parts = {}
	for i = 1, select("#", ...) do
		parts[#parts + 1] = tostring((select(i, ...)))
	end
	table.insert(out, table.concat(parts, " "))
end

local Shared = ReplicatedStorage:FindFirstChild("Shared")
local Cars = require(Shared.Cars)
local Chassis = require(Shared.Chassis)
local Server = ServerScriptService:FindFirstChild("Server", true)
local CarManager = require(Server.CarManager)

local pad = Instance.new("Part")
pad.Size = Vector3.new(3000, 8, 3000)
pad.Position = Vector3.new(0, 5000, 0)
pad.Anchored = true
pad.Material = Enum.Material.Concrete
pad.Parent = workspace
local padTop = pad.Position.Y + 4

local car = Cars.Get("gtr_r34")
local tuning = Chassis.tuningFor(car)
local LIMIT = tuning.MaxSteerAngle
local INSIDE = -20 -- comfortably inside +/-35.08

local function build(y)
	local m = CarManager._buildForDiag(car, tuning)
	m.Parent = workspace
	m:PivotTo(CFrame.new(0, y, 0))
	return m
end

local function servosOf(model)
	local servos, motors = {}, {}
	for _, d in ipairs(model:GetDescendants()) do
		if d:IsA("HingeConstraint") then
			if d.Name == Chassis.STEER_SERVO_NAME then
				table.insert(servos, d)
			elseif d.Name == Chassis.WHEEL_MOTOR_NAME then
				table.insert(motors, d)
			end
		end
	end
	return servos, motors
end

-- Run one case: returns the CurrentAngle trace.
local function runCase(label, opts)
	local m = build(opts.hoist and (padTop + 40) or (padTop + 3))
	local body = m.PrimaryPart
	local servos, motors = servosOf(m)

	if opts.hoist then
		body.Anchored = true
	end
	if opts.noWheel then
		for _, d in ipairs(m:GetDescendants()) do
			if d:IsA("BasePart") and d.Name:sub(1, 6) == "Wheel_" then
				d:Destroy()
			end
		end
	end
	if opts.motorOff then
		for _, mo in ipairs(motors) do
			mo.Enabled = false
		end
	end
	if opts.noLimits then
		for _, s in ipairs(servos) do
			s.LimitsEnabled = false
		end
	end

	for _ = 1, 60 do
		RunService.Heartbeat:Wait()
	end

	if opts.speed then
		body.AssemblyLinearVelocity = body.CFrame.LookVector * opts.speed
		for _, mo in ipairs(motors) do
			mo.MotorMaxTorque = 0
		end
	end

	for _, s in ipairs(servos) do
		s.TargetAngle = opts.target
	end

	local trace = {}
	for step = 1, 120 do
		if opts.speed then
			for _, s in ipairs(servos) do
				s.TargetAngle = opts.target
			end
		end
		if step % 24 == 0 then
			trace[#trace + 1] = string.format("%.1f", servos[1].CurrentAngle)
		end
		RunService.Heartbeat:Wait()
	end
	local final = servos[1].CurrentAngle
	local ok = math.abs(final - opts.target) < 5
	log(
		string.format(
			"%-42s target %6.1f -> [%s]  final %6.2f  %s",
			label,
			opts.target,
			table.concat(trace, " "),
			final,
			ok and "*** TURNS ***" or "stuck"
		)
	)
	m:Destroy()
end

log(
	string.format("limits +/-%.2f deg | INSIDE target %.1f | AngularSpeed %.1f rad/s", LIMIT, INSIDE, tuning.SteerSpeed)
)
log("")

runCase("A1 hoisted, target INSIDE limits", { hoist = true, target = INSIDE })
runCase("A2 hoisted, target AT limit", { hoist = true, target = -LIMIT })
runCase("A3 hoisted, LimitsEnabled=false", { hoist = true, target = INSIDE, noLimits = true })
runCase("A4 hoisted, wheels removed", { hoist = true, target = INSIDE, noWheel = true })
runCase("A5 hoisted, wheel motors disabled", { hoist = true, target = INSIDE, motorOff = true })
log("")
runCase("B1 ground static, target INSIDE", { target = INSIDE })
runCase("B2 ground static, motors disabled", { target = INSIDE, motorOff = true })
log("")
runCase("C1 ground coasting @60, INSIDE", { target = INSIDE, speed = 60 })
runCase("C2 ground coasting @120, INSIDE", { target = INSIDE, speed = 120 })

pad:Destroy()
return table.concat(out, "\n")