Multiple light sources in a tile-based lighting system - lua

Question

I have made a rudimentary tile based lighting system in ROBLOX by changing color based on distance from lightsource. I want to be able to put multiple lightsources, but I've ran into some problems:
The performance goes down a bit (from full 60 to 45-50) when I try to add another light source.
It doesn't work correctly, the lightsources cut out eachother's light and such.
my code:
local sp = script.Parent
local lightBrightness
local lightPower = 1
local grid = game.ReplicatedStorage.Folder:Clone()
grid.Parent = workspace.CurrentCamera
local lightSource = game.ReplicatedStorage.LightSource:Clone()
lightSource.Parent = workspace.CurrentCamera
lightSource.Position = grid:GetChildren()[math.random(1,#grid:GetChildren())].Position
for _, v in pairs(grid:GetChildren()) do
if v:IsA("Part") then
game["Run Service"].RenderStepped:connect(function()
local lightFact = (lightSource.Position-v.Position).magnitude
lightBrightness = lightPower - (lightFact*10)/255
if lightFact < 35 then
v.SurfaceGui.Frame.BackgroundColor3 = v.SurfaceGui.Frame.BackgroundColor3.r >= 0 and Color3.new((100/255)+lightBrightness*.85,(50/255)+lightBrightness*.85,10/255+lightBrightness) or Color3.new(0,0,0)
elseif lightFact > 35 and lightFact < 40 and v.SurfaceGui.Frame.BackgroundColor3.r > 0 then
v.SurfaceGui.Frame.BackgroundColor3 = Color3.new(0,0,0)
end
end)
end
end

Answer 1

The reason your code is running slowly is because the RenderStepped event runs every frame render, which is (typically) every 1/60th of a second. Try using the Stepped event to improve performance, as it only fires ever 1/30th of a second.
As for your light sources cancelling each other out, it appears from looking over your code that each light source affects the tiles around it without checking what light sources were affecting the tile before.
For example, light source A has a lightFact of 37 affecting tile A, so tile A changes it's appearance. Then, light source B, which is later in the loop, has a lightFact of 32. Well, the final lightFact value for that tile is going to be 32, effectively cancelling out the initial light sources effect.
In order to fix this issue, you need to store the current lightFact variable for each tile as you progress through the loop. My recommendation (alas, maybe not the fastest) would be to create a new Instance of IntValue inside of each tile, storing the current affecting lightFact value on the tile. Then, whenever a light source is about to check the tile, check if it has a child lightFact, and if it does, add that value to the lightFact value in your code. Therefore, the lightFact value you use to apply to the tile doesn't cancel out the last light source, because it incorporates that other lightsources lightFact value in its own calculation. Make sense?