diff --git a/rts/Lua/LuaUnsyncedCtrl.cpp b/rts/Lua/LuaUnsyncedCtrl.cpp
index 125838451c..90ed4652fe 100644
--- a/rts/Lua/LuaUnsyncedCtrl.cpp
+++ b/rts/Lua/LuaUnsyncedCtrl.cpp
@@ -171,6 +171,7 @@ bool LuaUnsyncedCtrl::PushEntries(lua_State* L)
 	REGISTER_LUA_CFUNC(AddWorldUnit);
 
 	REGISTER_LUA_CFUNC(DrawUnitCommands);
+	REGISTER_LUA_CFUNC(DrawBuildSquare);
 
 	REGISTER_LUA_CFUNC(SetTeamColor);
 
@@ -3382,6 +3383,54 @@ int LuaUnsyncedCtrl::SetBuildFacing(lua_State* L)
 }
 
 
+/***
+ *
+ * @function Spring.DrawBuildSquare
+ * @tparam {number,...} unitArray
+ * @tparam {cmdSpec,...} cmdArray
+ * @treturn {bool,...} canBuild
+ */
+int LuaUnsyncedCtrl::DrawBuildSquare(lua_State* L)
+{
+	vector<int> unitIDs;
+	ParseUnitArray(L, __func__, 1, unitIDs);
+
+	vector<Command> commands;
+	LuaUtils::ParseCommandArray(L, __func__, 2, commands);
+
+	vector<bool> canBuildVector(commands.size());
+
+	bool isQueued = !commands.empty() && (commands[0].GetOpts() & SHIFT_KEY);
+	vector<Command> conflicting;
+
+	for (int i=0; i<commands.size(); i++) {
+		Command cmd = commands[i];
+		if (cmd.GetID() >= 0) continue;
+
+		if (isQueued) {
+			conflicting.clear();
+			for (const int unitID: unitIDs) {
+				const CUnit* su = unitHandler.GetUnit(unitID);
+				const CCommandAI* cai = su->commandAI;
+				vector<Command> overlap = cai->GetOverlapQueued(cmd);
+				conflicting.insert(conflicting.end(), overlap.begin(), overlap.end());
+			}
+		}
+
+		canBuildVector[i] = unitDrawer->AddLuaBuildSquare(BuildInfo(cmd), conflicting);
+	}
+
+	lua_createtable(L, canBuildVector.size(), 0);
+	for (int i=0; i<canBuildVector.size(); i++) {
+		lua_pushboolean(L, canBuildVector[i]);
+		lua_rawseti(L, -2, 1 + i);
+	}
+
+	// TODO push canBuilds
+	return 1;
+}
+
+
 /******************************************************************************
  * UI
  * @section ui
diff --git a/rts/Lua/LuaUnsyncedCtrl.h b/rts/Lua/LuaUnsyncedCtrl.h
index d388fa9c53..d8156493f0 100644
--- a/rts/Lua/LuaUnsyncedCtrl.h
+++ b/rts/Lua/LuaUnsyncedCtrl.h
@@ -48,6 +48,7 @@ class LuaUnsyncedCtrl {
 		static int AddWorldUnit(lua_State* L);
 
 		static int DrawUnitCommands(lua_State* L);
+		static int DrawBuildSquare(lua_State* L);
 
 		static int SetTeamColor(lua_State* L);
 
diff --git a/rts/Rendering/Units/UnitDrawer.cpp b/rts/Rendering/Units/UnitDrawer.cpp
index ff26f05661..21cac8c04c 100644
--- a/rts/Rendering/Units/UnitDrawer.cpp
+++ b/rts/Rendering/Units/UnitDrawer.cpp
@@ -1183,7 +1183,6 @@ void CUnitDrawerLegacy::DrawIndividualDefAlpha(const SolidObjectDef* objectDef,
 bool CUnitDrawerLegacy::ShowUnitBuildSquare(const BuildInfo& buildInfo, const std::vector<Command>& commands) const
 {
 	RECOIL_DETAILED_TRACY_ZONE;
-	//TODO: make this a lua callin!
 	glDisable(GL_DEPTH_TEST);
 	glEnable(GL_BLEND);
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
@@ -1333,6 +1332,192 @@ bool CUnitDrawerLegacy::ShowUnitBuildSquare(const BuildInfo& buildInfo, const st
 	return canBuild;
 }
 
+bool CUnitDrawerLegacy::AddLuaBuildSquare(const BuildInfo& buildInfo, const std::vector<Command>& commands) {
+	CFeature* feature = nullptr;
+
+	struct BuildCache {
+		uint64_t key;
+		int createFrame;
+		bool canBuild;
+		std::vector<float3> buildableSquares; // buildable squares
+		std::vector<float3> featureSquares; // occupied squares
+		std::vector<float3> illegalSquares; // non-buildable squares
+	};
+
+	static std::vector<BuildCache> buildCache;
+
+	const float3& pos = buildInfo.pos;
+
+	uint64_t hashKey = spring::LiteHash(pos);
+	hashKey = spring::hash_combine(spring::LiteHash(buildInfo.buildFacing), hashKey);
+	/*
+	for (const auto& cmd : commands) {
+		const BuildInfo bc(cmd);
+		spring::hash_combine(spring::LiteHash(bc), hash);
+	}
+	*/
+
+	// the chosen number here is arbitrary, feel free to fine balance.
+	static constexpr int CACHE_VALIDITY_PERIOD = GAME_SPEED / 5;
+	std::erase_if(buildCache, [](const BuildCache& bc) {
+		return gs->frameNum - bc.createFrame >= CACHE_VALIDITY_PERIOD;
+	});
+
+	const float x1 = std::floor(pos.x - (buildInfo.GetXSize() * 0.5f * SQUARE_SIZE));
+	const float x2 = x1 + (buildInfo.GetXSize() * SQUARE_SIZE);
+	const float z1 = std::floor(pos.z - (buildInfo.GetZSize() * 0.5f * SQUARE_SIZE));
+	const float z2 = z1 + (buildInfo.GetZSize() * SQUARE_SIZE);
+	const float h = CGameHelper::GetBuildHeight(pos, buildInfo.def, false);
+
+	luaBuildPos.push_back(float3{x1, h, z1});
+	luaBuildPos.push_back(float3{x2, h, z2});
+
+	auto buildCacheItem = std::find_if(buildCache.begin(), buildCache.end(), [hashKey](const BuildCache& bc) {
+		return bc.key == hashKey;
+	});
+
+	if (buildCacheItem == buildCache.end()) {
+		buildCache.emplace_back();
+		buildCacheItem = buildCache.end()-1;
+
+		buildCacheItem->key = hashKey;
+		buildCacheItem->createFrame = gs->frameNum;
+		buildCacheItem->canBuild = CGameHelper::TestUnitBuildSquare(
+			buildInfo,
+			feature,
+			-1,
+			false,
+			&buildCacheItem->buildableSquares,
+			&buildCacheItem->featureSquares,
+			&buildCacheItem->illegalSquares,
+			&commands
+		);
+	}
+
+	bool canBuild = buildCacheItem->canBuild;
+	if (canBuild) {
+	luaBuildableSquares.insert(luaBuildableSquares.end(),
+		buildCacheItem->buildableSquares.begin(),
+		buildCacheItem->buildableSquares.end());
+	} else {
+	luaUnbuildableSquares.insert(luaUnbuildableSquares.end(),
+		buildCacheItem->buildableSquares.begin(),
+		buildCacheItem->buildableSquares.end());
+	}
+	luaFeatureSquares.insert(luaFeatureSquares.end(),
+		buildCacheItem->featureSquares.begin(),
+		buildCacheItem->featureSquares.end());
+	luaIllegalSquares.insert(luaIllegalSquares.end(),
+		buildCacheItem->illegalSquares.begin(),
+		buildCacheItem->illegalSquares.end());
+
+	return canBuild;
+}
+
+void CUnitDrawerLegacy::ShowLuaBuildSquare() {
+	if (luaBuildableSquares.empty() && luaUnbuildableSquares.empty() && luaFeatureSquares.empty() && luaIllegalSquares.empty()) {
+		return;
+	}
+
+	RECOIL_DETAILED_TRACY_ZONE;
+	glDisable(GL_DEPTH_TEST);
+	glEnable(GL_BLEND);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+	glDisable(GL_TEXTURE_2D);
+	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+
+	static constexpr std::array<float, 4> buildColorT  = { 0.0f, 0.9f, 0.0f, 0.7f };
+	static constexpr std::array<float, 4> buildColorF  = { 0.9f, 0.8f, 0.0f, 0.7f };
+	static constexpr std::array<float, 4> featureColor = { 0.9f, 0.8f, 0.0f, 0.7f };
+	static constexpr std::array<float, 4> illegalColor = { 0.9f, 0.0f, 0.0f, 0.7f };
+
+	static auto& rb = RenderBuffer::GetTypedRenderBuffer<VA_TYPE_C>();
+	rb.AssertSubmission();
+
+	auto& sh = rb.GetShader();
+
+	sh.Enable();
+
+	const float* color = &buildColorT[0];
+	for (const auto& buildableSquare : luaBuildableSquares) {
+		rb.AddQuadLines(
+			{ buildableSquare                                      , color },
+			{ buildableSquare + float3(SQUARE_SIZE, 0, 0          ), color },
+			{ buildableSquare + float3(SQUARE_SIZE, 0, SQUARE_SIZE), color },
+			{ buildableSquare + float3(0          , 0, SQUARE_SIZE), color }
+		);
+	}
+
+	color = &buildColorF[0];
+	for (const auto& unbuildableSquare : luaUnbuildableSquares) {
+		rb.AddQuadLines(
+			{ unbuildableSquare                                      , color },
+			{ unbuildableSquare + float3(SQUARE_SIZE, 0, 0          ), color },
+			{ unbuildableSquare + float3(SQUARE_SIZE, 0, SQUARE_SIZE), color },
+			{ unbuildableSquare + float3(0          , 0, SQUARE_SIZE), color }
+		);
+	}
+
+	color = &featureColor[0];
+	for (const auto& featureSquare : luaFeatureSquares) {
+		rb.AddQuadLines(
+			{ featureSquare                                      , color },
+			{ featureSquare + float3(SQUARE_SIZE, 0, 0          ), color },
+			{ featureSquare + float3(SQUARE_SIZE, 0, SQUARE_SIZE), color },
+			{ featureSquare + float3(0          , 0, SQUARE_SIZE), color }
+		);
+	}
+
+	color = &illegalColor[0];
+	for (const auto& illegalSquare : luaIllegalSquares) {
+		rb.AddQuadLines(
+			{ illegalSquare                                      , color },
+			{ illegalSquare + float3(SQUARE_SIZE, 0, 0          ), color },
+			{ illegalSquare + float3(SQUARE_SIZE, 0, SQUARE_SIZE), color },
+			{ illegalSquare + float3(0          , 0, SQUARE_SIZE), color }
+		);
+	}
+	rb.Submit(GL_LINES);
+
+	for (int i=0; i<luaBuildPos.size(); i+=2) {
+		float3 pos1 = luaBuildPos[i];
+		float3 pos2 = luaBuildPos[i+1];
+		float x1 = pos1.x, x2 = pos2.x;
+		float z1 = pos1.z, z2 = pos2.z;
+		float h = pos1.y;
+
+		if (h < 0.0f) {
+			constexpr uint8_t s[] = { 0,   0, 255, 128 }; // start color
+			constexpr uint8_t e[] = { 0, 128, 255, 255 }; // end color
+
+			rb.AddVertex({ float3(x1, h, z1), s }); rb.AddVertex({ float3(x1, 0.f, z1), e });
+			rb.AddVertex({ float3(x1, h, z2), s }); rb.AddVertex({ float3(x1, 0.f, z2), e });
+			rb.AddVertex({ float3(x2, h, z2), s }); rb.AddVertex({ float3(x2, 0.f, z2), e });
+			rb.AddVertex({ float3(x2, h, z1), s }); rb.AddVertex({ float3(x2, 0.f, z1), e });
+			rb.Submit(GL_LINES);
+
+			rb.AddVertex({ float3(x1, 0.0f, z1), e });
+			rb.AddVertex({ float3(x1, 0.0f, z2), e });
+			rb.AddVertex({ float3(x2, 0.0f, z2), e });
+			rb.AddVertex({ float3(x2, 0.0f, z1), e });
+			rb.Submit(GL_LINE_LOOP);
+		}
+	}
+
+	sh.Disable();
+
+
+	glEnable(GL_DEPTH_TEST);
+	//glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+	// glDisable(GL_BLEND);
+
+	luaBuildableSquares.clear();
+	luaUnbuildableSquares.clear();
+	luaFeatureSquares.clear();
+	luaIllegalSquares.clear();
+	luaBuildPos.clear();
+}
+
 void CUnitDrawerLegacy::DrawBuildIcons(const std::vector<CCursorIcons::BuildIcon>& buildIcons) const
 {
 	RECOIL_DETAILED_TRACY_ZONE;
diff --git a/rts/Rendering/Units/UnitDrawer.h b/rts/Rendering/Units/UnitDrawer.h
index c38350e694..860e4b6681 100644
--- a/rts/Rendering/Units/UnitDrawer.h
+++ b/rts/Rendering/Units/UnitDrawer.h
@@ -77,6 +77,9 @@ class CUnitDrawer : public CModelDrawerBase<CUnitDrawerData, CUnitDrawer>
 	        bool ShowUnitBuildSquare(const BuildInfo& buildInfo) const { return ShowUnitBuildSquare(buildInfo, std::vector<Command>()); }
 	virtual bool ShowUnitBuildSquare(const BuildInfo& buildInfo, const std::vector<Command>& commands) const = 0;
 
+	virtual bool AddLuaBuildSquare(const BuildInfo& buildInfo, const std::vector<Command>& commands) = 0;
+	virtual void ShowLuaBuildSquare() = 0;
+
 	virtual void DrawBuildIcons(const std::vector<CCursorIcons::BuildIcon>& buildIcons) const = 0;
 protected:
 	static bool ShouldDrawOpaqueUnit(CUnit* u, uint8_t thisPassMask);
@@ -144,6 +147,8 @@ class CUnitDrawerLegacy : public CUnitDrawerBase {
 	void DrawIndividualDefAlpha(const SolidObjectDef* objectDef, int teamID, bool rawState, bool toScreen = false) const override;
 
 	bool ShowUnitBuildSquare(const BuildInfo& buildInfo, const std::vector<Command>& commands) const override;
+	bool AddLuaBuildSquare(const BuildInfo& buildInfo, const std::vector<Command>& commands) override;
+	void ShowLuaBuildSquare() override;
 	void DrawBuildIcons(const std::vector<CCursorIcons::BuildIcon>& buildIcons) const override;
 
 	void DrawUnitMiniMapIcons() const override;
@@ -185,7 +190,11 @@ class CUnitDrawerLegacy : public CUnitDrawerBase {
 	void PopIndividualOpaqueState(const S3DModel* model, int teamID, bool deferredPass) const;
 	void PopIndividualAlphaState(const S3DModel* model, int teamID, bool deferredPass) const;
 protected:
-
+	std::vector<float3> luaBuildableSquares;
+	std::vector<float3> luaUnbuildableSquares;
+	std::vector<float3> luaFeatureSquares;
+	std::vector<float3> luaIllegalSquares;
+	std::vector<float3> luaBuildPos;
 };
 
 class CUnitDrawerFFP  final : public CUnitDrawerLegacy {};
diff --git a/rts/Rendering/WorldDrawer.cpp b/rts/Rendering/WorldDrawer.cpp
index ea01c6ef78..deb81cc632 100644
--- a/rts/Rendering/WorldDrawer.cpp
+++ b/rts/Rendering/WorldDrawer.cpp
@@ -462,6 +462,7 @@ void CWorldDrawer::DrawMiscObjects() const
 
 	mouse->DrawSelectionBox();
 	guihandler->DrawMapStuff(false);
+	unitDrawer->ShowLuaBuildSquare();
 
 	if (globalRendering->drawMapMarks && !game->hideInterface) {
 		inMapDrawerView->Draw();