Optimize ObjectiveArrow.lua (FAForever#4376)

lua/objectiveArrow.lua

@@ -1,63 +1,66 @@
 local Entity = import("/lua/sim/entity.lua").Entity
 
+---@class ObjectiveArrowSpec
+---@field AttachTo? Object
+---@field Size? number defaults to `1.0`
+
 ---@class ObjectiveArrow : Entity
 ObjectiveArrow = Class(Entity) {
 
     ---@param self ObjectiveArrow
-    ---@param spec table
-    OnCreate = function(self,spec)
-        self.BounceTime = 0.0
-        self.Size = spec.Size or 1.0
+    ---@param spec ObjectiveArrowSpec
+    OnCreate = function(self, spec)
+        -- unpack specs
+        local size = spec.Size or 1.0
+        local attachTo = spec.AttachTo
+
+        local arrowSize = size
         self:SetVizToFocusPlayer('Always')
         self:SetVizToEnemies('Intel')
         self:SetVizToAllies('Never')
         self:SetVizToNeutrals('Intel')
 
         self:SetMesh('/meshes/game/arrow_mesh')
 
-        local unitScale = 1.0
-
-        if spec.AttachTo then
-            spec.AttachTo.Trash:Add(self)
-            self:AttachBoneTo(-1,spec.AttachTo,-1)
+        if attachTo then
+            attachTo.Trash:Add(self)
+            self:AttachBoneTo(-1, attachTo, -1)
 
             -- Position at the top of the parent's collision box
             local yOff = 0
-            local extents = spec.AttachTo:GetCollisionExtents()
+            local extents = attachTo:GetCollisionExtents()
             if extents then
-                -- scale up arrow based on unit's size
-                unitScale = math.min( extents.Max.x - extents.Min.x, extents.Max.z - extents.Min.z)
-                unitScale = math.max( unitScale, 1.0 )
-
-                yOff = (self.Size * unitScale) / 2.0 + extents.Max.y - spec.AttachTo:GetPosition().y
-                yOff = yOff + 0.5
-            else
-                yOff = spec.Size / 2.0 + 0.5
+                local extentsMax, extentsMin = extents.Max, extents.Min
+                local unitSize = math.min(extentsMax.x - extentsMin.x, extentsMax.z - extentsMin.z)
+                -- scale up arrow size based on unit's extents if it ends up making it larger
+                if unitSize > 1 then
+                    arrowSize = arrowSize * unitSize
+                end
+                yOff = extentsMax.y - attachTo:GetPosition().y
             end
+            yOff = yOff + arrowSize * 0.5 + 0.5
 
-            self:SetParentOffset(Vector(0,yOff,0))
-            self.SavedOffset = yOff;
-            ForkThread(self.BounceThread,self)
+            ForkThread(self.BounceThread, self, yOff) -- handles the first `SetParentOffset` from the y offset
         end
 
         -- magic 0.4 scaling so spec.Size can be specified in OGrid units
-        self:SetDrawScale(0.4 * self.Size * unitScale)
+        self:SetDrawScale(0.4 * arrowSize)
     end,
 
     ---@param self ObjectiveArrow
-    BounceThread = function(self)
-        while true do
-            if self:BeenDestroyed() then
-                return
-            end
-
-            --LOG('sin =',math.sin(self.BounceTime))
-            local yOff = self.SavedOffset + math.sin(self.BounceTime) / 4
-
-            self:SetParentOffset( Vector(0,yOff,0) )
-
+    ---@param yOff number
+    BounceThread = function(self, yOff)
+        local vec = Vector(0, yOff, 0)
+        -- since the bounce change is pi/4, this will end up oscillating with a frequency of 8 like
+        -- 0 --> sqrt(2)/2 --> 1 --> sqrt(2)/2 --> 0 --> -sqrt(2)/2 --> -1 --> -sqrt(2)/2 --> 0
+        local bounceTime = 0
+        local bounceChng = math.pi * 0.25
+        while not self:BeenDestroyed() do
+            vec.y = yOff + math.sin(bounceTime) * 0.25
+            self:SetParentOffset(vec)
             WaitSeconds(0.1)
-            self.BounceTime = self.BounceTime + math.pi * 0.25
+
+            bounceTime = bounceTime + bounceChng
         end
     end,
-}
+}