From a16c4269a57e1c48ed03ed9f396737aeff3e0f9d Mon Sep 17 00:00:00 2001
From: 12345swordy <alexanderheistermann@gmail.com>
Date: Tue, 30 Jul 2024 22:01:54 -0500
Subject: [PATCH] Add ground trace ray functions

---
 rts/Lua/LuaSyncedRead.cpp | 78 +++++++++++++++++++++++++++++++++++++++
 rts/Lua/LuaSyncedRead.h   |  3 +-
 2 files changed, 80 insertions(+), 1 deletion(-)

diff --git a/rts/Lua/LuaSyncedRead.cpp b/rts/Lua/LuaSyncedRead.cpp
index a6bed0597d..e00da4188d 100644
--- a/rts/Lua/LuaSyncedRead.cpp
+++ b/rts/Lua/LuaSyncedRead.cpp
@@ -39,6 +39,7 @@
 #include "Sim/Misc/QuadField.h"
 #include "Sim/Misc/TeamHandler.h"
 #include "Sim/Misc/Wind.h"
+#include "Sim/Misc/CollisionHandler.h"
 #include "Sim/MoveTypes/StrafeAirMoveType.h"
 #include "Sim/MoveTypes/GroundMoveType.h"
 #include "Sim/MoveTypes/HoverAirMoveType.h"
@@ -379,6 +380,9 @@ bool LuaSyncedRead::PushEntries(lua_State* L)
 	REGISTER_LUA_CFUNC(GetFeaturePiecePosDir);
 	REGISTER_LUA_CFUNC(GetFeaturePieceMatrix);
 
+	REGISTER_LUA_CFUNC(TraceRayGroundInDirection);
+	REGISTER_LUA_CFUNC(TraceRayGroundBetweenPositions);
+
 	REGISTER_LUA_CFUNC(GetRadarErrorParams);
 
 	if (!LuaMetalMap::PushReadEntries(L))
@@ -8592,6 +8596,80 @@ int LuaSyncedRead::GetUnitScriptNames(lua_State* L)
 	return 1;
 }
 
+static int TraceRayGroundImpl(lua_State *const L, const float3 &pos, const float3 &dir, const float maxLen, const bool testWater)
+{
+	const float rayLength = CGround::LineGroundWaterCol(pos, dir, maxLen, testWater, CLuaHandle::GetHandleSynced(L));
+	if (rayLength == -1.0f)
+		return 0;
+
+	const auto collisionSpot = pos + dir * rayLength; // FIXME: would be nice if the CGround:: functions returned this so we wouldn't have to recalculate
+
+	lua_pushnumber(L, rayLength);
+	lua_pushnumber(L, collisionSpot.x);
+	lua_pushnumber(L, collisionSpot.y);
+	lua_pushnumber(L, collisionSpot.z);
+	return 4;
+}
+
+/*** Checks for a ground collision in given direction
+ *
+ * @function Spring.TraceRayGroundInDirection
+ *
+ * Checks if there is surface (ground, optionally water) towards a vector
+ * and returns the distance to the closest hit and its position, if any.
+ *
+ * @number posX
+ * @number posY
+ * @number posZ
+ * @number dirX
+ * @number dirY
+ * @number dirZ
+ * @bool[opt=true] testWater
+ * @treturn number rayLength
+ * @treturn number posX
+ * @treturn number posY
+ * @treturn number posZ
+ */
+int LuaSyncedRead::TraceRayGroundInDirection(lua_State* L)
+{
+	const float3 pos(luaL_checkfloat(L, 1), luaL_checkfloat(L, 2), luaL_checkfloat(L, 3));
+	const auto dir = float3(luaL_checkfloat(L, 4), luaL_checkfloat(L, 5), luaL_checkfloat(L, 6)).Normalize();
+	const float maxLen = luaL_optfloat(L, 7, 999999.f);
+	const bool testWater = luaL_optboolean(L, 8, true);
+
+	return TraceRayGroundImpl(L, pos, dir, maxLen, testWater);
+}
+
+/*** Checks for a ground collision between two positions
+ *
+ * @function Spring.TraceRayGroundBetweenPositions
+ *
+ * Checks if there is surface (ground, optionally water) between two positions
+ * and returns the distance to the closest hit and its position, if any.
+ *
+ * @number startX
+ * @number startY
+ * @number startZ
+ * @number endX
+ * @number endY
+ * @number endZ
+ * @bool[opt=true] testWater
+ * @treturn number rayLength
+ * @treturn number posX
+ * @treturn number posY
+ * @treturn number posZ
+ */
+int LuaSyncedRead::TraceRayGroundBetweenPositions(lua_State* L)
+{
+	const float3 start (luaL_checkfloat(L, 1), luaL_checkfloat(L, 2), luaL_checkfloat(L, 3));
+	const float3 end (luaL_checkfloat(L, 4), luaL_checkfloat(L, 5), luaL_checkfloat(L, 6));
+	const bool testWater = luaL_optboolean(L, 7, true);
+
+	const auto [dir, length] = (end - start).GetNormalized();
+
+	return TraceRayGroundImpl(L, start, dir, length, testWater);
+}
+
 
 /******************************************************************************
  * Misc
diff --git a/rts/Lua/LuaSyncedRead.h b/rts/Lua/LuaSyncedRead.h
index e6fae6952a..916fb97035 100644
--- a/rts/Lua/LuaSyncedRead.h
+++ b/rts/Lua/LuaSyncedRead.h
@@ -293,7 +293,8 @@ class LuaSyncedRead {
 		static int TraceRay(lua_State* L);           //TODO: not implemented
 		static int TraceRayUnits(lua_State* L);      //TODO: not implemented
 		static int TraceRayFeatures(lua_State* L);   //TODO: not implemented
-		static int TraceRayGround(lua_State* L);     //TODO: not implemented
+		static int TraceRayGroundBetweenPositions(lua_State* L);
+		static int TraceRayGroundInDirection(lua_State* L);
 };
 
 #endif /* LUA_SYNCED_READ_H */