From 02db521c80e071a5afd3b50760675df7850e362f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lars=20M=C3=BCller?=
 <34514239+appgurueu@users.noreply.github.com>
Date: Mon, 26 Aug 2024 21:22:38 +0200
Subject: [PATCH] Make getting bone overrides return the "same" euler angles
 (#15007)

---
 games/devtest/mods/unittests/entity.lua | 20 ++++++++++++++++++++
 src/activeobject.h                      |  3 +++
 src/script/lua_api/l_object.cpp         | 24 ++++++++++++++----------
 3 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/games/devtest/mods/unittests/entity.lua b/games/devtest/mods/unittests/entity.lua
index 38d026663..4e308d173 100644
--- a/games/devtest/mods/unittests/entity.lua
+++ b/games/devtest/mods/unittests/entity.lua
@@ -184,3 +184,23 @@ unittests.register("test_objects_in_area", function(_, pos)
 		return core.objects_in_area(pos:offset(-1, -1, -1), pos:offset(1, 1, 1))
 	end)
 end, {map=true})
+
+-- Tests that bone rotation euler angles are preserved (see #14992)
+local function test_get_bone_rot(_, pos)
+	local obj = core.add_entity(pos, "unittests:dummy")
+	for _ = 1, 100 do
+		local function assert_similar(euler_angles)
+			local _, rot = obj:get_bone_position("bonename")
+			assert(euler_angles:distance(rot) < 1e-3)
+			local override = obj:get_bone_override("bonename")
+			assert(euler_angles:distance(override.rotation.vec:apply(math.deg)) < 1e-3)
+		end
+		local deg = 1e3 * vector.new(math.random(), math.random(), math.random())
+		obj:set_bone_position("bonename", vector.zero(), deg)
+		assert_similar(deg)
+		local rad = 3 * math.pi * vector.new(math.random(), math.random(), math.random())
+		obj:set_bone_override("bonename", {rotation = {vec = rad}})
+		assert_similar(rad:apply(math.deg))
+	end
+end
+unittests.register("test_get_bone_rot", test_get_bone_rot, {map=true})
diff --git a/src/activeobject.h b/src/activeobject.h
index 52f997fdf..87b74d865 100644
--- a/src/activeobject.h
+++ b/src/activeobject.h
@@ -96,6 +96,9 @@ struct BoneOverride
 	{
 		core::quaternion previous;
 		core::quaternion next;
+		// Redundantly store the euler angles serverside
+		// so that we can return them in the appropriate getters
+		v3f next_radians;
 		bool absolute = false;
 		f32 interp_timer = 0;
 	} rotation;
diff --git a/src/script/lua_api/l_object.cpp b/src/script/lua_api/l_object.cpp
index 6baf146e5..dae2455e1 100644
--- a/src/script/lua_api/l_object.cpp
+++ b/src/script/lua_api/l_object.cpp
@@ -561,8 +561,10 @@ int ObjectRef::l_set_bone_position(lua_State *L)
 	BoneOverride props;
 	if (!lua_isnoneornil(L, 3))
 		props.position.vector = check_v3f(L, 3);
-	if (!lua_isnoneornil(L, 4))
-		props.rotation.next = core::quaternion(check_v3f(L, 4) * core::DEGTORAD);
+	if (!lua_isnoneornil(L, 4)) {
+		props.rotation.next_radians = check_v3f(L, 4) * core::DEGTORAD;
+		props.rotation.next = core::quaternion(props.rotation.next_radians);
+	}
 	props.position.absolute = true;
 	props.rotation.absolute = true;
 	sao->setBoneOverride(bone, props);
@@ -584,9 +586,9 @@ int ObjectRef::l_get_bone_position(lua_State *L)
 	std::string bone = readParam<std::string>(L, 2, "");
 	BoneOverride props = sao->getBoneOverride(bone);
 	push_v3f(L, props.position.vector);
-	v3f euler_rot;
-	props.rotation.next.toEuler(euler_rot);
-	push_v3f(L, euler_rot * core::RADTODEG);
+	// In order to give modders back the euler angles they passed in,
+	// this **must not** compute equivalent euler angles from the quaternion
+	push_v3f(L, props.rotation.next_radians * core::RADTODEG);
 	return 2;
 }
 
@@ -632,8 +634,10 @@ int ObjectRef::l_set_bone_override(lua_State *L)
 	lua_getfield(L, 3, "rotation");
 	if (!lua_isnil(L, -1)) {
 		lua_getfield(L, -1, "vec");
-		if (!lua_isnil(L, -1))
-			props.rotation.next = core::quaternion(check_v3f(L, -1));
+		if (!lua_isnil(L, -1)) {
+			props.rotation.next_radians = check_v3f(L, -1);
+			props.rotation.next = core::quaternion(props.rotation.next_radians);
+		}
 		lua_pop(L, 1);
 
 		read_prop_attrs(props.rotation);
@@ -671,9 +675,9 @@ static void push_bone_override(lua_State *L, const BoneOverride &props)
 
 	push_prop("position", props.position, props.position.vector);
 
-	v3f euler_rot;
-	props.rotation.next.toEuler(euler_rot);
-	push_prop("rotation", props.rotation, euler_rot);
+	// In order to give modders back the euler angles they passed in,
+	// this **must not** compute equivalent euler angles from the quaternion
+	push_prop("rotation", props.rotation, props.rotation.next_radians);
 
 	push_prop("scale", props.scale, props.scale.vector);