add reaply_lost_speed to KinematicCharacterController

Author: ntibi

src/control/character_controller.rs

@@ -105,6 +105,9 @@ pub struct KinematicCharacterController {
     pub offset: CharacterLength,
     /// Should the character try to slide against the floor if it hits it?
     pub slide: bool,
+    /// Should the speed lost because of collisions be applied to the final direction ?
+    /// Useless if sliding is not enabled
+    pub reapply_lost_speed: bool,
     /// Should the character automatically step over small obstacles?
     pub autostep: Option<CharacterAutostep>,
     /// The maximum angle (radians) between the floor’s normal and the `up` vector that the
@@ -124,6 +127,7 @@ impl Default for KinematicCharacterController {
             up: Vector::y_axis(),
             offset: CharacterLength::Relative(0.01),
             slide: true,
+            reapply_lost_speed: false,
             autostep: Some(CharacterAutostep::default()),
             max_slope_climb_angle: Real::frac_pi_4(),
             min_slope_slide_angle: Real::frac_pi_4(),
@@ -250,6 +254,7 @@ impl KinematicCharacterController {
                     toi,
                 });
 
+                let pre_slide_translation_remaining = translation_remaining;
                 // Try to go up stairs.
                 if !self.handle_stairs(
                     bodies,
@@ -267,6 +272,17 @@ impl KinematicCharacterController {
                     translation_remaining =
                         self.handle_slopes(&toi, &translation_remaining, &mut result);
                 }
+                if self.slide && self.reapply_lost_speed {
+                    let diff =
+                        pre_slide_translation_remaining.norm() - translation_remaining.norm();
+                    if let Some((normalized_dir, _)) =
+                        // threshold has to be > subtract_hit hardcoded correction, if not, we get made up movement in the direction of the hit normal
+                        UnitVector::try_new_and_get(translation_remaining, 1.0e-4)
+                    {
+                        // reapply the lost speed (but in the corrected direction)
+                        translation_remaining += *normalized_dir * diff;
+                    }
+                }
             } else {
                 // No interference along the path.
                 result.translation += translation_remaining;