Allow constructing Quat from two Vector3s

core/math/quat.h

@@ -71,6 +71,26 @@ class _NO_DISCARD_CLASS_ Quat {
 		r_axis.z = z * r;
 	}
 
+	void set_shortest_arc(const Vector3 &p_from, const Vector3 &p_to) {
+		Vector3 c = p_from.cross(p_to);
+		real_t d = p_from.dot(p_to);
+
+		if (d < -1 + (real_t)CMP_EPSILON) {
+			x = 0;
+			y = 1;
+			z = 0;
+			w = 0;
+		} else {
+			real_t s = Math::sqrt((1 + d) * 2);
+			real_t rs = 1 / s;
+
+			x = c.x * rs;
+			y = c.y * rs;
+			z = c.z * rs;
+			w = s * 0.5f;
+		}
+	}
+
 	void operator*=(const Quat &p_q);
 	Quat operator*(const Quat &p_q) const;
 
@@ -135,25 +155,8 @@ class _NO_DISCARD_CLASS_ Quat {
 		return *this;
 	}
 
-	Quat(const Vector3 &p_v0, const Vector3 &p_v1) // shortest arc
-	{
-		Vector3 c = p_v0.cross(p_v1);
-		real_t d = p_v0.dot(p_v1);
-
-		if (d < -1 + (real_t)CMP_EPSILON) {
-			x = 0;
-			y = 1;
-			z = 0;
-			w = 0;
-		} else {
-			real_t s = Math::sqrt((1 + d) * 2);
-			real_t rs = 1 / s;
-
-			x = c.x * rs;
-			y = c.y * rs;
-			z = c.z * rs;
-			w = s * 0.5f;
-		}
+	Quat(const Vector3 &p_v0, const Vector3 &p_v1) {
+		set_shortest_arc(p_v0, p_v1);
 	}
 
 	inline Quat() :

core/variant_call.cpp

@@ -518,6 +518,7 @@ struct _VariantCall {
 	VCALL_LOCALMEM0R(Quat, get_euler);
 	VCALL_LOCALMEM1(Quat, set_euler);
 	VCALL_LOCALMEM2(Quat, set_axis_angle);
+	VCALL_LOCALMEM2(Quat, set_shortest_arc);
 
 	VCALL_LOCALMEM0R(Color, to_argb32);
 	VCALL_LOCALMEM0R(Color, to_abgr32);
@@ -1906,6 +1907,7 @@ void register_variant_methods() {
 	ADDFUNC0R(QUAT, VECTOR3, Quat, get_euler, varray());
 	ADDFUNC1(QUAT, NIL, Quat, set_euler, VECTOR3, "euler", varray());
 	ADDFUNC2(QUAT, NIL, Quat, set_axis_angle, VECTOR3, "axis", REAL, "angle", varray());
+	ADDFUNC2(QUAT, NIL, Quat, set_shortest_arc, VECTOR3, "from", VECTOR3, "to", varray());
 
 	ADDFUNC0R(COLOR, INT, Color, to_argb32, varray());
 	ADDFUNC0R(COLOR, INT, Color, to_abgr32, varray());

doc/classes/Quat.xml

@@ -126,6 +126,13 @@
 				Sets the quaternion to a rotation specified by Euler angles (in the YXZ convention: when decomposing, first Z, then X, and Y last), given in the vector format as (X angle, Y angle, Z angle).
 			</description>
 		</method>
+		<method name="set_shortest_arc">
+			<argument index="0" name="from" type="Vector3" />
+			<argument index="1" name="to" type="Vector3" />
+			<description>
+				Makes this quaternion represent the shortest arc between [code]from[/code] and [code]to[/code]. These can be imagined as two points intersecting a sphere's surface, with a radius of [code]1.0[/code].
+			</description>
+		</method>
 		<method name="slerp">
 			<return type="Quat" />
 			<argument index="0" name="to" type="Quat" />