Auto Exposure

-- @ CloneTrooper1019, 2019

local Players = game:GetService("Players")
local Lighting = game:GetService("Lighting")
local RunService = game:GetService("RunService")

local player = Players.LocalPlayer
local up = Vector3.new(0, 1, 0)

local function getBrightness(color)
    local h, s, v = Color3.toHSV(color)
    return v
end

local function computeOcclusion(origin, dir)
    local occlusion = 0

    local ray = Ray.new(origin, dir.Unit * 5000)
    local ignoreList = {player.Character}

    while occlusion < 1 do
        local hit = workspace:FindPartOnRayWithIgnoreList(ray, ignoreList, false, true)

        if not hit then
            break
        end

        if hit.Transparency < 0.95 and hit.CastShadow then
            local opacity = math.clamp(1 - hit.Transparency, 0, 1)
            local blockDepth = (hit.Size.Magnitude * opacity) / 20
            occlusion = math.min(1, occlusion + blockDepth)
        end

        table.insert(ignoreList, hit)
    end

    return occlusion
end

local function update(deltaTime)
    local camera = workspace.CurrentCamera

    if not camera then
        return
    end

    local origin = camera.CFrame.Position
    local sunDir = Lighting:GetSunDirection()
    local dayLight = math.clamp(sunDir.Y * 10, -0.5, 1)

    if dayLight < 0 then
        sunDir = Lighting:GetMoonDirection()
    end

    local indoorLevel = computeOcclusion(origin, up)
    local sunOcclusion = computeOcclusion(origin, sunDir)

    local indoorLight = getBrightness(Lighting.Ambient)
    local outdoorLight = getBrightness(Lighting.OutdoorAmbient)

    local strength = 1 - (outdoorLight + ((indoorLight - outdoorLight) * indoorLevel))
    local target = sunOcclusion * strength * dayLight * 3

    local current = Lighting.ExposureCompensation

    if (current < target) then
        current = math.min(target, current + deltaTime)
    elseif (current > target) then
        current = math.max(target, current - (deltaTime * 2))
    end

    Lighting.ExposureCompensation = current
end

RunService:BindToRenderStep("AutoExposure", 201, update)