fix: use ySorting

sonic-bluestreak.love/birb/modules/world/world3D.lua

@@ -80,7 +80,7 @@ function World3D:getVisibleActors(id)
     actors = self:getActors()
   end
 
-  actors = self:zSortItems(actors)
+  actors = self:ySortItems(actors)
 
   return actors
 end
@@ -182,6 +182,79 @@ end
 -- DRAW FUNCTIONS
 -- Functions to draw the world
 
+function World3D:ySortItems(items)
+  -- zSorting algorithm taken from bump3D example, adapted to gamecore.
+  local graph = Tsort.new()
+  local noOverlap = {}
+
+  -- Iterate through all visible items, and calculate ordering of all pairs
+  -- of overlapping items.
+  for _, itemA in ipairs(items) do repeat
+    local x, y, w, h = self.shapes:getRect(itemA)
+    local otherItemsFilter = function(other) return other ~= itemA end
+    local overlapping, len = self.shapes:queryRect(x, y, w, h, otherItemsFilter)
+
+    if len == 0 then
+      table.insert(noOverlap, itemA)
+
+      break
+    end
+
+    local _, aY, aZ, _, aH, aD = self.bodies:getCube(itemA.mainHitbox)
+    local aDepth, aID, aType
+    aDepth  = itemA.depth
+    aID     = itemA.creationID
+    aType   = itemA.type
+    aZ     = math.ceil(aZ)
+    aY     = math.ceil(aY)
+
+    for _, itemB in ipairs(overlapping) do
+      local _, bY, bZ, _, bH, bD = self.bodies:getCube(itemB.mainHitbox)
+      local bDepth, bID, bType
+      bDepth = itemB.depth
+      bID    = itemB.creationID
+      bType  = itemB.type
+      bZ     = math.ceil(bZ)
+      bY     = math.ceil(bY)
+
+      if aY < bY then
+        -- item A is completely behind item B
+        graph:add(itemA, itemB)
+      elseif bY < aY then
+        -- item B is completely behind item A
+        graph:add(itemB, itemA)
+      else
+        -- item A's forward-most point is the same than item B's forward-most point
+        if aDepth > bDepth then
+          graph:add(itemB, itemA)
+        elseif aDepth < bDepth then
+          graph:add(itemA, itemB)
+        else
+          if aID > bID then
+            graph:add(itemA, itemB)
+          elseif aID < bID then
+            graph:add(itemB, itemA)
+          else
+            error("two object can't have the same ID")
+          end
+        end
+      end
+    end
+  until true end
+
+  local sorted, err = graph:sort()
+  if err then
+    error(err)
+  end
+  for _, item in ipairs(noOverlap) do
+    table.insert(sorted, item)
+  end
+
+  return sorted
+
+end
+
+
 function World3D:zSortItems(items)
   -- zSorting algorithm taken from bump3D example, adapted to gamecore.
   local graph = Tsort.new()
@@ -189,7 +262,6 @@ function World3D:zSortItems(items)
 
   -- Iterate through all visible items, and calculate ordering of all pairs
   -- of overlapping items.
-  -- TODO: Each pair is calculated twice currently. Maybe this is slow?
   for _, itemA in ipairs(items) do repeat
     local x, y, w, h = self.shapes:getRect(itemA)
     local otherItemsFilter = function(other) return other ~= itemA end