fix(zones): draw complex polygons properly

convex polygons are split into triangles more simply
complex polygons are split into trapezoids and then triangles to be drawn

imports/zones/client.lua

@@ -1,6 +1,151 @@
 local glm = require 'glm'
 local zones = {}
 
+local function getTriangles(polygon)
+	local X = {}
+	X[1], X[2] = polygon.projectToAxis(polygon, vec(1, 0, 0))
+
+	local points = {}
+	local sides = {}
+	local triangles = {}
+
+	for i = 1, #polygon do
+		sides[i] = {polygon[i], polygon[i + 1] or polygon[1]}
+		points[polygon[i]] = {side = i, intersects = {}, v = polygon[i], uses = 0}
+	end
+
+	for i = 1, #polygon do
+		for j = 1, #X do
+			local extremePoint = vec(X[j], polygon[i].yz)
+			if polygon[i].x ~= extremePoint.x then
+				for l = 1, #polygon do
+					local bool, d, d2 = glm.segment.intersectsSegment(polygon[i], extremePoint, polygon[l], polygon[l + 1] or polygon[1])
+					if d > 0.001 and d < 0.999 and d2 > 0.001 and d2 < 0.999 then
+						local intersect = glm.segment.getPoint(polygon[i], extremePoint, d)
+						local valid = polygon.contains(polygon, (polygon[i] + intersect) / 2)
+						if valid then
+							for m = 1, #polygon do
+								local bool, d, d2 = glm.segment.intersectsSegment(polygon[i], intersect, polygon[m], polygon[m + 1] or polygon[1])
+								if d > 0.001 and d < 0.999 and d2 > 0.001 and d2 < 0.999 then
+									valid = false
+									break
+								end
+							end
+						end
+						if valid then
+							points[intersect] = {side = l, vertex = polygon[i], v = intersect, uses = 0}
+							points[polygon[i]].intersects[#points[polygon[i]].intersects + 1] = intersect
+
+							sides[l][#sides[l] + 1] = intersect
+						end
+					end
+				end
+			end
+		end
+	end
+
+	function up(a, b)
+		return a.y > b.y
+	end
+
+	function down(a, b)
+		return a.y < b.y
+	end
+
+	function makeTriangles(t)
+		if t.c and t.d then
+			triangles[#triangles + 1] = {a = t.a, b = t.b, c = t.c}
+			triangles[#triangles + 1] = {a = t.b, b = t.c, c = t.d}
+			for k, v in pairs(t) do
+				points[v].uses += 1
+			end
+		else
+			triangles[#triangles + 1] = {a = t.a, b = t.b or t.c, c = t.d or t.c}
+			for k, v in pairs(t) do
+				points[v].uses += 2
+			end
+		end
+	end
+
+	for i = 1, #sides do
+		local side = sides[i]
+		local direction = side[1].y - side[2].y
+		if direction > 0 then
+			direction = up
+		else
+			direction = down
+		end
+		table.sort(side, direction)
+		for j = 1, #side - 1 do
+			local a, b = side[j], side[j + 1]
+			local c = points[a].vertex or points[a].intersects[1]
+			local d = points[b].vertex or points[b].intersects[1]
+			if points[a].uses < 2 then
+				if c and d then
+					if points[c].side ~= points[d].side then
+						local c2
+						if points[a].vertex then
+							if points[a].v == points[c].intersects[1] and points[c].intersects?[2] then
+								c2 = points[c].intersects[2]
+							else
+								c2 = points[c].intersects[1]
+							end
+						else
+							c2 = points[a].intersects[2]
+						end
+						local c2Point = points[c2]
+						if c2Point and c2Point.side == points[d].side then
+							c = c2
+						else
+							if points[b].vertex then
+								if points[b].v == points[d].intersects[1] and points[d].intersects?[2] then
+									d = points[d].intersects[2]
+								elseif b ~= points[d].intersects[1] then
+									d = points[d].intersects[1]
+								end
+							elseif points[b].intersects[2] then
+								d = points[b].intersects[2]
+							end
+						end
+					end
+				elseif c then
+					if points[b].side ~= points[c].side then
+						local c2
+						if points[c].intersects?[2] then
+							c2 = points[c].intersects[2]
+						elseif points[a].intersects?[2] then
+							c2 = points[a].intersects[2]
+						end
+						local c2Point = points[c2]
+						if c2Point then
+							if c2Point.side == points[b].side or (c2Point.side - #sides + 1) == points[b].side then
+								c = c2
+							end
+						end
+					end
+				elseif d then
+					if points[a].side ~= points[d].side then
+						local d2
+						if points[d].intersects?[2] then
+							d2 = points[d].intersects[2]
+						elseif points[b].intersects?[2] then
+							d2 = points[b].intersects[2]
+						end
+						local d2Point = points[d2]
+						if d2Point then
+							if d2Point.side == points[a].side or (d2Point.side - #sides + 1) == points[a].side then
+								d = d2
+							end
+						end
+					end
+				end
+				makeTriangles({a = a, b = b, c = c, d = d})
+			end
+		end
+	end
+	return triangles
+end
+
 local function removeZone(self)
 	zones[self.id] = nil
 end
@@ -9,14 +154,17 @@ local function debug(self)
 	local polygon = self.polygon
 	local polyCount = #self.polygon
 
-    for i = 1, polyCount do
-        if i == polyCount then
-            DrawPoly(polygon[i], polygon[1], self.centroid, 255, 0, 0, 50)
-            DrawPoly(polygon[1], polygon[i], self.centroid, 255, 0, 0, 50)
-        else
-            DrawPoly(polygon[i], polygon[i + 1], self.centroid, 255, 0, 0, 50)
-            DrawPoly(polygon[i + 1], polygon[i], self.centroid, 255, 0, 0, 50)
-        end
+	if polygon.isConvex(polygon) then
+		for i = 2, polyCount - 1 do
+			DrawPoly(polygon[1], polygon[i], polygon[i + 1], 255, 0, 0, 50)
+			DrawPoly(polygon[i], polygon[1], polygon[i + 1], 255, 0, 0, 50)
+		end
+	else
+		self.triangles = self.triangles or getTriangles(polygon)
+		for i = 1, #self.triangles do
+			DrawPoly(self.triangles[i].a, self.triangles[i].b, self.triangles[i].c, 255, 0, 0, 50)
+			DrawPoly(self.triangles[i].b, self.triangles[i].a, self.triangles[i].c, 255, 0, 0, 50)
+		end
     end
 end