vFire: Improved Integration (#1549)

With TTT2 v0.13.0 we started supporting vFire in TTT2. This pullrequest
improves the integration by reworking the game effects function to use
the vFire particles when vFire is installed. I added a `0.5` modifier to
the vFire fire particles as they were quite large and almost
overwhelming. Now they are more tuned to TTT2. However I doubled the
damage ticks so it more closely matches that of normal TTT.

This PR also adds a hook replacement to the vFire explosion handling
reported in #1478. The issue here is that it was applied to all
entities, but it shouldn't be applied to players. I couldn't really test
this one as I was unable to reproduce the issue due to loading order.
See the issue for more details.

Also maybe it is a good idea if @EntranceJew could take a look at this
as well because he worked more with vFire than I did.

vFire docs:
https://docs.google.com/document/d/1GbSrWMqJYI0f4pP0pYBiG2TsKUCXifQLjCqC0qHA9a0/edit

CHANGELOG.md

@@ -42,6 +42,7 @@ All notable changes to TTT2 will be documented here. Inspired by [keep a changel
 - Added `admin.IsAdmin(ply)` as a wrapper that automatically calls `GM:TTT2AdminCheck` (by @TimGoll)
   - Made sure this new function is used in our whole codebase for all admin checks
 - Added `ENTITY:IsPlayerRagdoll` to check if a corpse is a real player ragdoll (by @TimGoll)
+- Added improved vFire integration for everything in TTT2 that spawns fire (by @TimGoll and @EntranceJew)
 - Added the `SWEP.DryFireSound` field to the weapon base to allow the dryfire sound to be easily changed (by @TW1STaL1CKY)
 - Added role derandomization options for perceptually fairer role distribution
 
@@ -90,6 +91,7 @@ All notable changes to TTT2 will be documented here. Inspired by [keep a changel
 - 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)
+- Fixed vFire explosions killing a player even if they have `NoExplosionDamage` equipped (by @TimGoll)
 - Fixed a nil error in the PreDrop function in weapon_ttt_cse (by @mexikoedi)
 - Fixed `table.FullCopy(tbl)` behaviour when `tbl` contained a Vector or Angle (by @Histalek)
 - Fixed the bodysearch showing a wrong player icon when searching a fake body (by @TimGoll)

lua/ttt2/libraries/game_effects.lua

@@ -43,6 +43,18 @@ function gameEffects.StartFires(
         local vstart = pos + tr.HitNormal * 64
         local ttl = lifetime + math.Rand(-lifetimeVariance, lifetimeVariance)
 
+        if vFireInstalled then
+            flames[#flames + 1] = CreateVFireBall(
+                ttl,
+                0.5 * size,
+                vstart,
+                0.5 * ang:Forward() * forceSpread,
+                dmgowner
+            )
+
+            continue
+        end
+
         local flame = ents.Create("ttt_flame")
         flame:SetPos(vstart)
         flame:SetFlameSize(size)
@@ -135,3 +147,43 @@ function gameEffects.RadiusDamage(dmginfo, pos, radius, inflictor)
         end
     end
 end
+
+-- vFIRE INTEGRATION
+
+if SERVER then
+    -- This is a replacement hook for the explosion damage hook in vFire. The difference here is
+    -- that it is only applied if the damage is for non-player entities.
+    --
+    -- original doc: Fix fire dependent entities' behaviors, for instance:
+    -- Explosive barrels rely on being ignited to explode after damaged by an explosion themselves
+    -- Because vFire removes default fires, we need to encourage more chain explosions
+    local function vFireTakeDamageReplacement(ent, dmg)
+        ---
+        -- @realm server
+        -- stylua: ignore
+        if hook.Run("vFireSuppressExplosionBehavior") then
+            return
+        end
+
+        if not IsValid(ent) or not ent:IsPlayer() or not dmg:IsExplosionDamage() then
+            return
+        end
+
+        local hp = ent:Health()
+        if hp < dmg:GetDamage() and hp > 0 and math.random(1, 3) == 1 then
+            ent:SetHealth(0)
+        end
+    end
+
+    hook.Add("TTT2FinishedLoading", "TTT2TweakvFire", function()
+        if not vFireInstalled then
+            return
+        end
+
+        -- increase the think rate of fires to increase the damage dealt by fire
+        vFireBurnThinkTickRate = 0.75
+
+        hook.Remove("EntityTakeDamage", "vFireFixExplosion")
+        hook.Add("EntityTakeDamage", "vFireFixExplosionReplacement", vFireTakeDamageReplacement)
+    end)
+end