[GMod] Car Physics Jitter Fix Test

gmod-car-physics-jitter-fix-test.lua

--@name Mini Car Test
--@author Name
--@server

local owner, client, chip, world = owner(), player(), chip(), entity(0)

-------------------------------------------

local custom_forces = true -- Set this to `true` to workaround a physics jitter bug
local size = Vector(32, 20, 2)
local body_mass = 100

local convexes = {
	{
		-- Vector(0, 0, 20),
		Vector(size.x / 2, -size.y / 2, -size.z / 2), Vector(-size.x / 2, -size.y / 2, -size.z / 2), Vector(size.x / 2, size.y / 2, -size.z / 2), Vector(-size.x / 2, size.y / 2, -size.z / 2),
		Vector(size.x / 2, -size.y / 2,  size.z / 2), Vector(-size.x / 2, -size.y / 2,  size.z / 2), Vector(size.x / 2, size.y / 2,  size.z / 2), Vector(-size.x / 2, size.y / 2,  size.z / 2),
	}
}

local body = prop.createCustom(chip:getPos() + chip:getUp() * 22, chip:getAngles(), convexes, true)
local body_phys = body:getPhysicsObject()
body_phys:setMass(body_mass)

-------------------------------------------

local wheels = {
	{ origin = Vector( size.x / 2,  size.y / 2, -size.z / 2), holo = hologram.create(Vector(), Angle(), "models/holograms/cube.mdl", Vector(0.2)) }, -- Front Left
	{ origin = Vector( size.x / 2, -size.y / 2, -size.z / 2), holo = hologram.create(Vector(), Angle(), "models/holograms/cube.mdl", Vector(0.2)) }, -- Front Right
	{ origin = Vector(-size.x / 2,  size.y / 2, -size.z / 2), holo = hologram.create(Vector(), Angle(), "models/holograms/cube.mdl", Vector(0.2)) }, -- Rear Left
	{ origin = Vector(-size.x / 2, -size.y / 2, -size.z / 2), holo = hologram.create(Vector(), Angle(), "models/holograms/cube.mdl", Vector(0.2)) }, -- Rear Right
}

local suspension_length = 20
local suspension_rest_length = 10

local suspension_strength = 150
local suspension_damping = 10

-------------------------------------------

-- hook.add("Tick", "", function() -- works as well
body:setPhysicsUpdateListener(function()
	local force_linear, force_torque = Vector(), Vector()
	local suspension_direction = body:getUp()
	
	for _, wheel in ipairs(wheels) do
		local origin = body:localToWorld(wheel.origin)
		
		local ray = trace.line(origin, origin - suspension_direction * suspension_length, body)
		wheel.holo:setPos(ray.HitPos)
		
		if ray.Hit then
			local suspension_velocity = suspension_direction:dot(body_phys:getVelocityAtPoint(origin))
			local suspension_offset = suspension_rest_length - suspension_length * ray.Fraction
			local suspension_force = (suspension_offset * suspension_strength) - (suspension_velocity * suspension_damping)
			
			local linear, torque = body_phys:calculateForceOffset(suspension_direction * suspension_force, origin)
			force_linear = force_linear + linear
			force_torque = force_torque + torque
		end
	end
	
	if custom_forces then
		body:setCustomPropForces(force_torque * 10, force_linear * 100, 4)
	else
		force_torque = body_phys:localToWorldVector(force_torque)
		body_phys:applyForceCenter(force_linear)
		body_phys:applyTorque(force_torque)
	end
	
end)