1 files changed, 48 insertions, 16 deletions

diff --git a/core/math/quaternion.cpp b/core/math/quaternion.cpp
index 11bfcc1a6f..c681c60694 100644
--- a/core/math/quaternion.cpp
+++ b/core/math/quaternion.cpp
@@ -111,7 +111,7 @@ Quaternion Quaternion::log() const {
 Quaternion Quaternion::exp() const {
 	Quaternion src = *this;
 	Vector3 src_v = Vector3(src.x, src.y, src.z);
-	float theta = src_v.length();
+	real_t theta = src_v.length();
 	if (theta < CMP_EPSILON) {
 		return Quaternion(0, 0, 0, 1);
 	}
@@ -132,15 +132,9 @@ Quaternion Quaternion::slerp(const Quaternion &p_to, const real_t &p_weight) con
 	// adjust signs (if necessary)
 	if (cosom < 0.0f) {
 		cosom = -cosom;
-		to1.x = -p_to.x;
-		to1.y = -p_to.y;
-		to1.z = -p_to.z;
-		to1.w = -p_to.w;
+		to1 = -p_to;
 	} else {
-		to1.x = p_to.x;
-		to1.y = p_to.y;
-		to1.z = p_to.z;
-		to1.w = p_to.w;
+		to1 = p_to;
 	}
 
 	// calculate coefficients
@@ -189,16 +183,54 @@ Quaternion Quaternion::slerpni(const Quaternion &p_to, const real_t &p_weight) c
 			invFactor * from.w + newFactor * p_to.w);
 }
 
-Quaternion Quaternion::cubic_slerp(const Quaternion &p_b, const Quaternion &p_pre_a, const Quaternion &p_post_b, const real_t &p_weight) const {
+Quaternion Quaternion::spherical_cubic_interpolate(const Quaternion &p_b, const Quaternion &p_pre_a, const Quaternion &p_post_b, const real_t &p_weight) const {
 #ifdef MATH_CHECKS
 	ERR_FAIL_COND_V_MSG(!is_normalized(), Quaternion(), "The start quaternion must be normalized.");
 	ERR_FAIL_COND_V_MSG(!p_b.is_normalized(), Quaternion(), "The end quaternion must be normalized.");
 #endif
-	//the only way to do slerp :|
-	real_t t2 = (1.0f - p_weight) * p_weight * 2;
-	Quaternion sp = this->slerp(p_b, p_weight);
-	Quaternion sq = p_pre_a.slerpni(p_post_b, p_weight);
-	return sp.slerpni(sq, t2);
+	Quaternion from_q = *this;
+	Quaternion pre_q = p_pre_a;
+	Quaternion to_q = p_b;
+	Quaternion post_q = p_post_b;
+
+	// Align flip phases.
+	from_q = Basis(from_q).get_rotation_quaternion();
+	pre_q = Basis(pre_q).get_rotation_quaternion();
+	to_q = Basis(to_q).get_rotation_quaternion();
+	post_q = Basis(post_q).get_rotation_quaternion();
+
+	// Flip quaternions to shortest path if necessary.
+	bool flip1 = signbit(from_q.dot(pre_q));
+	pre_q = flip1 ? -pre_q : pre_q;
+	bool flip2 = signbit(from_q.dot(to_q));
+	to_q = flip2 ? -to_q : to_q;
+	bool flip3 = flip2 ? to_q.dot(post_q) <= 0 : signbit(to_q.dot(post_q));
+	post_q = flip3 ? -post_q : post_q;
+
+	// Calc by Expmap in from_q space.
+	Quaternion ln_from = Quaternion(0, 0, 0, 0);
+	Quaternion ln_to = (from_q.inverse() * to_q).log();
+	Quaternion ln_pre = (from_q.inverse() * pre_q).log();
+	Quaternion ln_post = (from_q.inverse() * post_q).log();
+	Quaternion ln = Quaternion(0, 0, 0, 0);
+	ln.x = Math::cubic_interpolate(ln_from.x, ln_to.x, ln_pre.x, ln_post.x, p_weight);
+	ln.y = Math::cubic_interpolate(ln_from.y, ln_to.y, ln_pre.y, ln_post.y, p_weight);
+	ln.z = Math::cubic_interpolate(ln_from.z, ln_to.z, ln_pre.z, ln_post.z, p_weight);
+	Quaternion q1 = from_q * ln.exp();
+
+	// Calc by Expmap in to_q space.
+	ln_from = (to_q.inverse() * from_q).log();
+	ln_to = Quaternion(0, 0, 0, 0);
+	ln_pre = (to_q.inverse() * pre_q).log();
+	ln_post = (to_q.inverse() * post_q).log();
+	ln = Quaternion(0, 0, 0, 0);
+	ln.x = Math::cubic_interpolate(ln_from.x, ln_to.x, ln_pre.x, ln_post.x, p_weight);
+	ln.y = Math::cubic_interpolate(ln_from.y, ln_to.y, ln_pre.y, ln_post.y, p_weight);
+	ln.z = Math::cubic_interpolate(ln_from.z, ln_to.z, ln_pre.z, ln_post.z, p_weight);
+	Quaternion q2 = to_q * ln.exp();
+
+	// To cancel error made by Expmap ambiguity, do blends.
+	return q1.slerp(q2, p_weight);
 }
 
 Quaternion::operator String() const {
@@ -213,7 +245,7 @@ Vector3 Quaternion::get_axis() const {
 	return Vector3(x * r, y * r, z * r);
 }
 
-float Quaternion::get_angle() const {
+real_t Quaternion::get_angle() const {
 	return 2 * Math::acos(w);
 }