Incendiary: Fixed explosion sometimes missing fire (#1544)

Fixes #1427

This pullrequests fixes the issue with incediaries not spawning fire
particles (or spawning them in the next room if there is any) when
exploding close to a wall. The relevant change for this fix is in the
base grenade file:


![image](https://github.com/TTT-2/TTT2/assets/13639408/64c9b037-0143-4c20-9164-ecc40e8fbf98)

This is not a TTT2 issue, it also [exists in vanilla
TTT](https://github.com/Facepunch/garrysmod/blob/master/garrysmod/gamemodes/terrortown/entities/entities/ttt_basegrenade_proj.lua#L54).
The issue exists because the trace, that should detect the ground, does
not ignore the grenade itself and returns therefore a kind of random
HitNormal. Since the grenade is then moved along the normal prior to
explosion, this often resulted in the grenade being behing a wall and
therefore not spawning any particles.

Adding `self` to the filter would fix this issue as well, but after some
quick thought I decided that `MASK_SOLID_BRUSHONLY` would be a fitting
mask setting here. [[docs]](https://wiki.facepunch.com/gmod/Enums/MASK).

This issue probably existed with ALL GRENADES that inherited from the
weapon base. I wonder why nobody besides me ever reported this. Probably
because you do not notice it during normal chaotic gameplay.

Besides this change I also renamed some variables to be more in-line
with our style, while also moving the fire grenade decal creation to the
server. That way the decal spawns together with the explosion and not a
few moments before. It looks cleaner that way.

CHANGELOG.md

@@ -85,6 +85,7 @@ All notable changes to TTT2 will be documented here. Inspired by [keep a changel
 - Fixed a nil compare error in the DrawHUD function in weapon_tttbasegrenade (by @mexikoedi)
 - Fixed players sometimes not receiving their role if they joined late to the game (by @TimGoll)
 - Fixed weapon dryfire sound interrupting the weapon's gunshot sound (by @TW1STaL1CKY)
+- Fixed incendiaries sometimes exploding without fire (by @TimGoll)
 - Fixed scoreboard not showing any body search info on players that changed to forced spec during a round (by @TimGoll)
 
 ### Removed

gamemodes/terrortown/entities/entities/ttt_basegrenade_proj.lua

@@ -56,28 +56,31 @@ end
 ---
 -- @ignore
 function ENT:Think()
-    local etime = self:GetExplodeTime() or 0
-    if etime ~= 0 and etime < CurTime() then
+    local timeExplosion = self:GetExplodeTime() or 0
+
+    if timeExplosion ~= 0 and timeExplosion < CurTime() then
+        local thrower = self:GetThrower()
+
         -- if thrower disconnects before grenade explodes, just don't explode
-        if SERVER and (not IsValid(self:GetThrower())) then
+        if SERVER and (not IsValid(thrower)) then
             self:Remove()
-            etime = 0
+
             return
         end
 
         -- find the ground if it's near and pass it to the explosion
-        local spos = self:GetPos()
+        local pos = self:GetPos()
         local tr = util.TraceLine({
-            start = spos,
-            endpos = spos + Vector(0, 0, -32),
-            mask = MASK_SHOT_HULL,
-            filter = self.thrower,
+            start = pos,
+            endpos = pos + Vector(0, 0, -32),
+            mask = MASK_SOLID_BRUSHONLY,
         })
 
         local success, err = pcall(self.Explode, self, tr)
         if not success then
             -- prevent effect spam on Lua error
             self:Remove()
+
             ErrorNoHaltWithStack("ERROR CAUGHT: ttt_basegrenade_proj: " .. err .. "\n")
         end
     end

gamemodes/terrortown/entities/entities/ttt_firegrenade_proj.lua

@@ -32,46 +32,44 @@ end
 ---
 -- @ignore
 function ENT:Explode(tr)
-    if SERVER then
-        self:SetNoDraw(true)
-        self:SetSolid(SOLID_NONE)
+    self:SetDetonateExact(0)
 
-        -- pull out of the surface
-        if tr.Fraction ~= 1.0 then
-            self:SetPos(tr.HitPos + tr.HitNormal * 0.6)
-        end
+    if CLIENT then
+        return
+    end
 
-        local pos = self:GetPos()
+    self:SetNoDraw(true)
+    self:SetSolid(SOLID_NONE)
 
-        if util.PointContents(pos) == CONTENTS_WATER then
-            self:Remove()
-            return
-        end
+    -- pull out of the surface
+    if tr.Fraction ~= 1.0 then
+        self:SetPos(tr.HitPos + tr.HitNormal * 0.6)
+    end
 
-        local effect = EffectData()
-        effect:SetStart(pos)
-        effect:SetOrigin(pos)
-        effect:SetScale(self:GetRadius() * 0.3)
-        effect:SetRadius(self:GetRadius())
-        effect:SetMagnitude(self.dmg)
+    local pos = self:GetPos()
 
-        if tr.Fraction ~= 1.0 then
-            effect:SetNormal(tr.HitNormal)
-        end
+    if util.PointContents(pos) == CONTENTS_WATER then
+        self:Remove()
 
-        util.Effect("Explosion", effect, true, true)
+        return
+    end
 
-        util.BlastDamage(self, self:GetThrower(), pos, self:GetRadius(), self:GetDmg())
+    local effect = EffectData()
+    effect:SetStart(pos)
+    effect:SetOrigin(pos)
+    effect:SetScale(self:GetRadius() * 0.3)
+    effect:SetRadius(self:GetRadius())
+    effect:SetMagnitude(self.dmg)
 
-        gameEffects.StartFires(pos, tr, 10, 20, false, self:GetThrower(), 500, false, 128, 2)
+    if tr.Fraction ~= 1.0 then
+        effect:SetNormal(tr.HitNormal)
+    end
 
-        self:SetDetonateExact(0)
+    util.PaintDown(pos, "Scorch", self)
+    util.Effect("Explosion", effect, true, true)
+    util.BlastDamage(self, self:GetThrower(), pos, self:GetRadius(), self:GetDmg())
 
-        self:Remove()
-    else
-        local spos = self:GetPos()
-        util.PaintDown(spos, "Scorch", self)
+    gameEffects.StartFires(pos, tr, 10, 20, false, self:GetThrower(), 500, false, 128, 2)
 
-        self:SetDetonateExact(0)
-    end
+    self:Remove()
 end

lua/ttt2/libraries/game_effects.lua

@@ -2,6 +2,7 @@
 -- A library to consolidate some common effects code.
 -- @author EntranceJew
 -- @module gameEffects
+
 if SERVER then
     AddCSLuaFile()
 end
@@ -11,35 +12,36 @@ gameEffects = {}
 ---
 -- Create a bundle of fires all from a central location.
 -- This is used for incendiary grenades or C4 detonation.
--- @param Vector pos The position the fires should originate from.
--- @param TraceResult tr A trace to orient the creation of the fires around.
--- @param number num The number of individual balls of fire that should be created.
--- @param number lifetime The base lifetime of all fires in the bundle.
--- @param boolean explode Should the fires explode when they reach the end of their lives?
--- @param nil|Player dmgowner The player to attribute the fire damage to.
--- @param number spread_force The force that each fire will be flung with.
--- @param boolean immobile If true, fires will become stationary once they begin burning.
--- @param number size The physical scale of the fires.
--- @param number lifetime_variance The amount each lifetime for each fire can vary.
--- @return table A table full of the fire entities.
+-- @param Vector pos The position the fires should originate from
+-- @param TraceResult tr A trace to orient the creation of the fires around
+-- @param number amount The number of individual balls of fire that should be created
+-- @param number lifetime The base lifetime of all fires in the bundle
+-- @param boolean explode Should the fires explode when they reach the end of their lives
+-- @param nil|Player dmgowner The player to attribute the fire damage to
+-- @param number forceSpread The force that each fire will be flung with
+-- @param boolean immobile If true, fires will become stationary once they begin burning
+-- @param number size The physical scale of the fires
+-- @param number lifetimeVariance The amount each lifetime for each fire can vary
+-- @return table A table full of the fire entities
 -- @realm shared
 function gameEffects.StartFires(
     pos,
     tr,
-    num,
+    amount,
     lifetime,
     explode,
     dmgowner,
-    spread_force,
+    forceSpread,
     immobile,
     size,
-    lifetime_variance
+    lifetimeVariance
 )
     local flames = {}
-    for i = 1, num do
+
+    for i = 1, amount do
         local ang = Angle(-math.Rand(0, 180), math.Rand(0, 360), math.Rand(0, 360))
         local vstart = pos + tr.HitNormal * 64
-        local ttl = lifetime + math.Rand(-lifetime_variance, lifetime_variance)
+        local ttl = lifetime + math.Rand(-lifetimeVariance, lifetimeVariance)
 
         local flame = ents.Create("ttt_flame")
         flame:SetPos(vstart)
@@ -62,7 +64,7 @@ function gameEffects.StartFires(
         if IsValid(phys) then
             -- the balance between mass and force is subtle, be careful adjusting
             phys:SetMass(2)
-            phys:ApplyForceCenter(ang:Forward() * spread_force)
+            phys:ApplyForceCenter(ang:Forward() * forceSpread)
             phys:AddAngleVelocity(Vector(ang.p, ang.r, ang.y))
         end
 
@@ -74,14 +76,14 @@ end
 
 ---
 -- Creates a single point of fire.
--- @param Vector pos The position to create the fire at.
--- @param number scale Controls the height of the flame more than its radius. Informs the size.
--- @param number life_span How long a fire will burn for.
--- @param nil|Entity owner The creator of the fire.
--- @param nil|Entity parent The thing to attach the fire to.
--- @return nil|Entity The fire it created, or nil if it was merged / couldn't be created.
+-- @param Vector pos The position to create the fire at
+-- @param number scale Controls the height of the flame more than its radius. Informs the size
+-- @param number lifetime How long a fire will burn for
+-- @param nil|Entity owner The creator of the fire
+-- @param nil|Entity parent The thing to attach the fire to
+-- @return nil|Entity The fire it created, or nil if it was merged / couldn't be created
 -- @realm server
-function gameEffects.SpawnFire(pos, scale, life_span, owner, parent)
+function gameEffects.SpawnFire(pos, scale, lifetime, owner, parent)
     local fire = ents.Create("env_fire")
 
     if not IsValid(fire) then
@@ -91,12 +93,15 @@ function gameEffects.SpawnFire(pos, scale, life_span, owner, parent)
     fire:SetParent(parent)
     fire:SetOwner(owner)
     fire:SetPos(pos)
+
     --no glow + delete when out + start on + last forever
     fire:SetKeyValue("spawnflags", tostring(128 + 32 + 4 + 2 + 1))
+
     -- hardly controls size, hitbox is goofy, impossible to work with
     fire:SetKeyValue("firesize", tostring(scale))
-    fire:SetKeyValue("health", tostring(life_span))
+    fire:SetKeyValue("health", tostring(lifetime))
     fire:SetKeyValue("ignitionpoint", "64")
+
     -- don't hurt the player because we're managing the hurtbox ourselves
     fire:SetKeyValue("damagescale", "0")
     fire:Spawn()
@@ -106,8 +111,8 @@ function gameEffects.SpawnFire(pos, scale, life_span, owner, parent)
 end
 
 ---
--- greatly simplified version of SDK's game_shard/gamerules.cpp:RadiusDamage
--- does no block checking, radius should be very small
+-- Greatly simplified version of SDK's game_shard/gamerules.cpp:RadiusDamage
+-- does no block checking, radius should be very small.
 -- @note only hits players!
 -- @param DamageInfo dmginfo
 -- @param Vector pos