From c53a711a9140b8c4ac34135ed8bb35fe0e9af692 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20B=C3=B6klin?= <ludvig.boklin@protonmail.com>
Date: Sun, 6 Jun 2021 15:43:50 +0200
Subject: [PATCH] Prevent rotation from negative lift and fix glider ori in
 wield state

---
 common/src/states/glide_wield.rs         |  4 ++--
 common/systems/src/phys.rs               | 29 +++++++++++++-----------
 voxygen/anim/src/character/glidewield.rs |  3 ++-
 3 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/common/src/states/glide_wield.rs b/common/src/states/glide_wield.rs
index 4a2b1a7cd1..93b007b417 100644
--- a/common/src/states/glide_wield.rs
+++ b/common/src/states/glide_wield.rs
@@ -36,8 +36,8 @@ impl CharacterBehavior for Data {
         glider.ori = glider.ori.slerped_towards(
             Ori::from(data.inputs.look_dir)
                 .yawed_towards(data.ori.look_dir())
-                .pitched_up(inline_tweak::tweak!(0.7)),
-            inline_tweak::tweak!(3.0) * data.dt.0,
+                .pitched_up(inline_tweak::tweak!(0.5)),
+            inline_tweak::tweak!(5.0) * data.dt.0,
         );
 
         // If not on the ground while wielding glider enter gliding state
diff --git a/common/systems/src/phys.rs b/common/systems/src/phys.rs
index f1217f13ad..587d57a78f 100644
--- a/common/systems/src/phys.rs
+++ b/common/systems/src/phys.rs
@@ -54,25 +54,28 @@ fn integrate_glider_forces(
         _ => None,
     }?;
 
-    let dv_ = Some(dt.0 * glider.aerodynamic_forces(&rel_wind, AIR_DENSITY))
+    let glider_rel_dv = Some(dt.0 * glider.aerodynamic_forces(&rel_wind, AIR_DENSITY))
         .filter(|imp| !imp.is_approx_zero())
         .map(|imp| imp / mass.0 - dv)?;
 
-    vel.0 += dv_;
+    vel.0 += glider_rel_dv;
 
     {
-        let glider_dir = ori.up();
+        let char_up = ori.up();
         let glider_dist = tweak!(1.0);
-        let glider_pos = *glider_dir * glider_dist;
-        if let Some(rot) = Dir::from_unnormalized(glider_pos + dv_)
-            .map(|u| {
-                let s = glider_dir.dot(*u).powf(tweak!(10.0) * dt.0);
-                glider_dir.slerped_to(
-                    u,
-                    tweak!(-0.7) + tweak!(1.0) * s.max(0.0) + tweak!(0.0) * s.min(0.0),
-                )
-            })
-            .map(|u| glider_dir.rotation_between(u))
+        let glider_pos = *char_up * glider_dist;
+
+        let glider_up = glider.ori.up();
+
+        let mut dr = glider_rel_dv;
+        // remove negative lift (for aesthetic reasons and because greater values of dv
+        // rotates too much)
+        let dn = glider_rel_dv.dot(*glider_up);
+        if dn.is_sign_negative() {
+            dr -= dn * *glider_up / glider_up.magnitude_squared()
+        }
+        if let Some(rot) =
+            Dir::from_unnormalized(glider_pos + dr).map(|u| char_up.rotation_between(u))
         {
             *ori = ori.prerotated(rot);
         }
diff --git a/voxygen/anim/src/character/glidewield.rs b/voxygen/anim/src/character/glidewield.rs
index e142946b12..6adfd7ebe7 100644
--- a/voxygen/anim/src/character/glidewield.rs
+++ b/voxygen/anim/src/character/glidewield.rs
@@ -23,7 +23,8 @@ impl Animation for GlideWieldAnimation {
         s_a: &SkeletonAttr,
     ) -> Self::Skeleton {
         let mut next = (*skeleton).clone();
-        let glider_ori = orientation.inverse() * glider_orientation;
+        let glider_ori = (orientation * next.torso.orientation * next.chest.orientation).inverse()
+            * glider_orientation;
         let glider_pos = Vec3::new(0.0, -5.0, 13.0);
         *rate = 1.0;