Invisible bots

[dufft-angrygermantryhard]

Hi, I had some issues stopping bots from turning invisible on my server and eventually realized this seemed to be an ongoing issue (seemed to still be marked as TODO within supervisor.lua). I mostly managed to solve this (models may still bug out, but atleast they dont turn invisible anymore)
Is there a chance this could be the actual fix? Is there maybe more that needs to be done than I first realized? This so far seems to have worked fine for me.

Main differences were the use of SetTransmitWithParent, checking for potential invalid alpha levels, and trying to use different render mode. At the same time, i tried giving the application of the status in gamemode/init.lua a quick timer application (timer.simple with 0.1 delay) because i feel like it couldve been a race condition?

Within gamemode/init.lua (at local overridemodel = pl:GetZombieClassTable().OverrideModel):

local overridemodel = pl:GetZombieClassTable().OverrideModel
		if overridemodel then
			timer.Simple(0.1, function() if not IsValid(pl) or not pl:Alive() then return end
				local current = pl:GiveStatus("overridemodel")
				if current and current:IsValid() then
					current:SetModel(overridemodel)
					current:SetOwner(pl) -- Ensure owner is explicitly set to attempt to fix the problem
					current:ResetBones()
					pl:CallZombieFunction1("ManipulateOverrideModel", current)
					
				end
			end)
			
		else
			pl:RemoveStatus("overridemodel", false, true)
		end

Within zombiesurvival/entities/entities/status_overridemodel.lua:

AddCSLuaFile()

ENT.Type = "anim"
ENT.Base = "status__base"
ENT.RenderGroup = RENDERGROUP_TRANSLUCENT

function ENT:Initialize()
	self:SetSolid(SOLID_NONE)
	self:SetMoveType(MOVETYPE_NONE)
	self:SetTransmitWithParent(true)		-- attempt at fixing the issue with invisibility, as parents seem to break on ModelOverride
	self:AddEffects(bit.bor(EF_BONEMERGE, EF_BONEMERGE_FASTCULL, EF_PARENT_ANIMATES))
	--self:SetRenderMode(RENDERMODE_TRANSALPHA)

	local pPlayer = self:GetOwner()
	if pPlayer:IsValid() then
		pPlayer.status_overridemodel = self
		if SERVER and (pPlayer:Team() ~= TEAM_UNDEAD or not pPlayer:GetZombieClassTable().NoHideMainModel) then
		
			-- more attempts at a fix by using different render mode
			--pPlayer:SetRenderMode(RENDERMODE_NONE)
			-- should hopefully fix issue (i dont think this worked lol)
			pPlayer:SetRenderMode(RENDERMODE_TRANSLAPHA)
			pPlayer:SetColor(Color(255,255,255,0))
		end
	end
end

function ENT:PlayerSet(pPlayer, bExists)
	if SERVER and pPlayer:Team() ~= TEAM_UNDEAD or not pPlayer:GetZombieClassTable().NoHideMainModel then
		-- more attempts at a fix by using different render mode
		--pPlayer:SetRenderMode(RENDERMODE_NONE)
		-- should hopefully fix issue (i dont think this worked lol)
		pPlayer:SetRenderMode(RENDERMODE_TRANSALPHA)
		pPlayer:SetColor(Color(255,255,255,0))
	end
end

function ENT:OnRemove()
	local pPlayer = self:GetOwner()
	if SERVER and pPlayer:IsValid() then
		pPlayer:SetRenderMode(RENDERMODE_NORMAL)
	end
end

function ENT:Think()
end

if CLIENT then
	function ENT:Draw()
		local owner = self:GetOwner()
		if owner:IsValid() and (not owner:IsPlayer() or owner:Alive()) then
			local pcolor = owner:GetColor() or Color(255,255,255,255)	-- failsafe attempt
			
			-- Attempt at a fix; trying to failsafe the alpha levels
			if pcolor.a <= 0 and (not owner.SpawnProtection) then
				pcolor.a = 255
			end
			
			if owner.SpawnProtection then
				pcolor.a = (0.02 + (CurTime() + self:EntIndex() * 0.2) % 0.05) * 255
				pcolor.r = 0
				pcolor.b = 0
				pcolor.g = 255
				render.SuppressEngineLighting(true)
			end
			self:SetColor(pcolor)
			
			-- trying to force the game to realize if theres some issues 
			if not (owner.SpawnProtection and owner:GetZombieClassTable().NoHideMainModel) then
				if not owner:CallZombieFunction1("PrePlayerDrawOverrideModel", self) then
					self:DrawModel()

					owner:CallZombieFunction1("PostPlayerDrawOverrideModel", self)
				end
			end

			if owner.SpawnProtection then
				render.SuppressEngineLighting(false)
			end
		end
	end
	ENT.DrawTranslucent = ENT.Draw
end

[Dadido3]

Just for completeness, the following issues show the same or similar problems:

• Bots occasionally lose their playermodels #64
• Invisible zombies (GAMEBREAKING) #69 and its followup with a solution: Update about invisible bots. #74

Is there a chance this could be the actual fix? Is there maybe more that needs to be done than I first realized? This so far seems to have worked fine for me.

The last issue i linked above seems to point to the same mechanic (OverrideModel), so i guess that's where the bug originates from. But no idea if your code fully fixes the problem, or just makes it more unlikely to appear. I don't have deep knowledge of the different ZS codebases, so i would need to tinker/debug that myself to figure out the root cause. But anyways, thanks a lot for the investigation and for your solution.

[Dadido3]

Just a quick question: how likely does the bug appear for you, and what is your setup (Exact ZS version, any addons used)? I would like to test and reproduce this here (some time in the future).

Maybe there is a way to adjust bot (re)spawning in a way that stops triggering this.

[dufft-angrygermantryhard]

My apologies for not noticing the previous threads. Ill make sure to search next time and add to those

Yeah im highly certain that OverrideModel is the cause. During a small timeframe where i accidentally bricked the OverrideModel code without realizing it, the bug completely stopped appearing but instead broke some custom models like the Chem Zombies or Skeletal Crawlers

Regarding But no idea if your code fully fixes the problem, or just makes it more unlikely to appear.
I have not seen this bug happen since I implemented my fixes, but I have seen models break like the Chem Zombies on rare occasions where the Chem Zombies on our server just instead started using the Skeleton model in a T-Pose position
I can provide a picture of how it looks like when the zombie model is now "broken" but it basically means the failsafe mustve worked somewhere, as before that, they were completely invisible (will also provide that)
Need to dig through my recordings to show the still images to you, but I will do it as soon as possible in this thread

Regarding what is your setup (Exact ZS version, any addons used)
We have been using our own version of ZS which was branched off of Noxiousnet and was passed on to me under the name Bol Shodka ZS, it incorporates the TFA Base and BS Content 1-4 + "dufft_zs_content_test" in the Workshop, but nothing else than that outside of maps. I think this can be pulled off with standard nox aswell and I can try to help if needed, you would just have to let bots spawn as classes that they normally would never pick (like headcrabs and chem zombie)

Regarding how likely does the bug appear for you
Ever since the fix attempt, not at all. Before that, it seemed to happen basically at any point past wave 2, but most commonly during wave 2-4; I tracked it down to chemical zombies, frigid revenants and Crawler classes causing the issue, especially the dark black zombie models (i forgor name)

According to another developer that I was speaking to via discord (The Bassline Father), this bug seems to get more common the more you mess with zombie classes and their models, but from what I noticed, it seems to happen commonly with classes that have completely different model structures (e.g. headcrab -> suicide -> bot swaps to Chem Zombie, or chem zombie -> suicide -> crawler)

[dufft-angrygermantryhard]

Broken chem zombie

Normal chem zombie

Cant seem to reproduce the fixed-but-wonky-due-to-failsafe chem zombie right now, but I will add onto this comment if I see it happen during normal play
Also no stress, im happy to help out <3

[Dadido3]

I currently don't have a setup to test with a specific gamemode, can you check if the problem still appears when there are no suiciding bots?

Comment out these lines (And look for similar lines in case you have added stuff to D3bot):

• D3bot/lua/d3bot/sv_zs_bot_handler/handlers/undead_headcrab.lua

  Line 66 in 37c28f8

  if majorStuck and GAMEMODE:GetWaveActive() then bot:Kill() end

• D3bot/lua/d3bot/sv_zs_bot_handler/handlers/undead_fallback.lua

  Line 82 in 37c28f8

  if majorStuck and GAMEMODE:GetWaveActive() then bot:Kill() end

• D3bot/lua/d3bot/sv_zs_bot_handler/basics.lua

  Line 20 in 37c28f8

  bot:Kill()

This should stop bots from killing themselves. It's possible that the way they suicide is somehow triggering the issue. Just a guess, but may be worth a try.

Or did you encounter invisible zombies that were definitely killed by survivors prior to respawn?

[dufft-angrygermantryhard]

Yeah, we have encountered invisible zombies that were definetly killed by survivors before sadly, its why the issue was so hard to track down at first for me. I dont think stopping them from suiciding would change anything

[dufft-angrygermantryhard]

One of my guesses could be that some form of ragdolling has something to do with it aswell. We had adjusted the quicksilver to ragdoll and knock down zombies on hit - i ended up having to remove this (seperately from the bugfixes above) as it caused a zombies model to completely break if they never went back to the normal Zombie at any point in time. Eradicators became completely invisible on a knockdown for example. ZS really doesnt like it when you try to ragdoll-knockdown zombies

So far though from quick testing while trying to replicate the fucked models; when it normally wouldve gone invisible, they immediately become visible after spawning instead of staying "invisible until leaving the spawn", though im not sure if it is something related to a stack overflow fix attempt on our server.

In my server update log i wrote this down on 23th february 2026, since then we havent seen this bug again, so I think its an issue with the way the models didnt carry over the parent model before?

23/02/2026-A
attempt fix #4
kill me
Added SetTransmitWithParent and tried to fix a potential race condition within the visibility code