Implement directional influence

assets/game_settings.ron

@@ -24,7 +24,8 @@
         visual_shake_table: [
             -3.0, -1.5, 1.5, 3.0
         ],
-        attacker_visual_shake_multiplier: 0.4
+        attacker_visual_shake_multiplier: 0.4,
+        di_max_angle: "18.0"
     ),
     stage_manifest_paths: [
         "stages/battlefield/test.stage.ron"

src/fighter/attack/directional_influence.rs

@@ -0,0 +1,57 @@
+use fixed::traits::ToFixed;
+use fixed_math::SinCos;
+
+use crate::math::{
+    int::{FGWide, FGi32},
+    vec::FGVec2,
+};
+
+/// Applies DI to a given attack direction
+pub fn apply_directional_influence(
+    receiver_stick: FGVec2,
+    attack_angle: FGi32,
+    di_max_angle: FGi32,
+) -> FGVec2 {
+    let (sin, cos) = attack_angle.sin_cos();
+    let base_launch_direction = FGVec2::new(cos, sin);
+
+    let Some(base_launch_direction) = base_launch_direction.normalize() else {
+        return FGVec2::ZERO;
+    };
+
+    if receiver_stick.length_squared().is_zero() {
+        return base_launch_direction;
+    }
+
+    let normal = FGVec2::new(-base_launch_direction.y, base_launch_direction.x);
+    let di_amount = receiver_stick.dot(normal);
+    let angle_change = di_amount * di_max_angle.to_fixed::<FGWide>();
+    let (sin, cos) = (attack_angle + angle_change.to_fixed::<FGi32>()).sin_cos();
+    FGVec2::new(cos, sin).normalize_or_zero()
+}
+
+#[cfg(test)]
+mod test {
+use crate::{
+        fighter::attack::directional_influence::apply_directional_influence,
+        math::{int::FGi32, vec::FGVec2},
+    };
+
+    #[test]
+    fn di_zero_passes_unmodified() {
+        let di = apply_directional_influence(FGVec2::ZERO, FGi32::lit("0.0"), FGi32::lit("18.0"));
+        const EPSILON: FGi32 = FGi32::from_bits(4);
+        assert!(di.x.abs_diff(FGi32::ONE) < EPSILON);
+        assert!(di.y.abs_diff(FGi32::ZERO) < EPSILON);
+    }
+
+    #[test]
+    fn di_applies_on_the_correct_side() {
+        let di = apply_directional_influence(FGVec2::lit("0.0", "1.0"), FGi32::lit("0.0"), FGi32::lit("18.0"));
+        assert!(di.x > FGi32::ZERO);
+        assert!(di.y > FGi32::ZERO);
+        let di = apply_directional_influence(FGVec2::lit("0.0", "-1.0"), FGi32::lit("0.0"), FGi32::lit("18.0"));
+        assert!(di.x > FGi32::ZERO);
+        assert!(di.y < FGi32::ZERO);
+    }
+}

src/fighter/attack/mod.rs

@@ -1,6 +1,7 @@
 use std::collections::{HashMap, VecDeque};
 
 mod reaction;
+pub mod directional_influence;
 
 use bevy::ecs::entity::{EntityMapper, MapEntities};
 use bevy::prelude::*;
@@ -42,7 +43,7 @@ pub enum HitReactionKind {
 
 #[derive(Debug, Hash, Clone)]
 pub struct FighterHitReaction {
-    pub launch_velocity: FGVec2,
+    pub launch_velocity: FGi32,
     pub launch_angle: FGi32,
     pub hitstop_frames: HitStop,
     pub hitstun_frames: u32,

src/fighter/attack/reaction.rs

@@ -1,12 +1,11 @@
 use bevy::prelude::*;
 use bevy_ggrs::prelude::GgrsSchedule;
-use fixed_math::SinCos;
 
 use super::*;
 use crate::{
     fighter::{
         Fighter, FighterFacingDirection, FighterHitboxes, FighterHitstop, FighterHitstopShake, FighterHitstopShakeKind, FighterHitstopShakeRole, FighterPendingHitReaction, FighterStaleMoveQueue, errors::FighterErrors, manifest::FighterManifest, state::FighterState,
-    }, game_settings::GameSettings, math::{int::FGi32, vec::FGVec2}, player::Player, schedule::GameplaySet, scripting::FighterAttackScript,
+    }, game_settings::GameSettings, math::{int::FGi32}, player::Player, schedule::GameplaySet, scripting::FighterAttackScript,
 };
 
 pub fn resolve_fighter_hits(
@@ -90,14 +89,13 @@ pub fn resolve_fighter_hits(
             } else {
                 angle
             };
-            let (sin, cos) = launch_angle.sin_cos();
+
-            let launch_direction = FGVec2::new(cos, sin);
             let hitstop = HitStop::calculate(FighterDamage(attack_damage), false);
             reactions.push((
                 attacker_entity,
                 attacker_slot,
                 FighterHitReaction {
-                    launch_velocity: launch_direction * knockback.get_launch_speed(&game_settings),
+                    launch_velocity: knockback.get_launch_speed(&game_settings),
                     launch_angle,
                     hitstun_frames: knockback.get_hitstun_frames(&game_settings),
                     hitstop_frames: hitstop,

src/fighter/debug.rs

@@ -9,7 +9,7 @@ use bevy_egui::{EguiContexts, egui};
 use crate::debug_tools::{DebugSettings, FighterDebugRowKind};
 use crate::fighter::animation::FighterAnimationFrame;
 use crate::fighter::attack::{
-    FighterKnockbackVelocity, FighterLastAttackDebug, FighterPendingHitReaction,
+    self, FighterKnockbackVelocity, FighterLastAttackDebug, FighterPendingHitReaction,
     FighterSolvedHurtboxes,
 };
 use crate::fighter::baked_animation::{BakedFighterAnimations, FighterBoneMatrices};
@@ -382,12 +382,13 @@ pub fn attack_debug_gather(
         &FighterPendingHitReaction,
         &FighterTranslation,
         &Fighter,
+        &FighterInput,
     )>,
     mut commands: Commands,
     manifests: Res<Assets<FighterManifest>>,
     game_settings: Res<GameSettings>,
 ) -> Result {
-    for (entity, reaction, translation, fighter) in query {
+    for (entity, reaction, translation, fighter, input) in query {
         let Some(ref hit) = reaction.0 else {
             continue;
         };
@@ -396,7 +397,13 @@ pub fn attack_debug_gather(
             .get(&fighter.manifest)
             .ok_or(FighterErrors::FighterManifestNotFound)?;
 
-        let mut knockback_vel = FighterKnockbackVelocity(hit.launch_velocity);
+        let launch_dir = attack::directional_influence::apply_directional_influence(
+            input.get_last_frame().movement,
+            hit.launch_angle,
+            game_settings.fighter_common.di_max_angle,
+        );
+
+        let mut knockback_vel = FighterKnockbackVelocity(launch_dir * hit.launch_velocity);
         let mut fighter_vel = FighterVelocity(FGVec2::ZERO);
         let mut translation = Vec3::new(translation.x.to_num(), translation.y.to_num(), 0.0);
 

src/fighter/state/hitstun.rs

@@ -1,8 +1,6 @@
 use crate::{
     fighter::{
-        animation::AnimKind,
+        animation::AnimKind, attack::{self, FighterHitReaction}, state::{
-        attack::FighterHitReaction,
-        state::{
             CollisionContext, EnterContext, ExitContext, FighterState, FighterStateImpl,
             InterruptContext, UpdateContext, air,
             fall::FallState,
@@ -10,8 +8,7 @@ use crate::{
             land::LandingType,
             wait::WaitState,
         },
-    },
+    }, math::int::FGi32,
-    math::int::FGi32,
 };
 
 #[derive(Clone, Debug, Hash)]
@@ -24,6 +21,7 @@ pub enum HitstopStateKind {
 pub struct HitstunState {
     pub hit_reaction: FighterHitReaction,
     pub hitstop_kind: HitstopStateKind,
+    knockback_applied: bool
 }
 
 impl FighterStateImpl for HitstunState {
@@ -59,6 +57,17 @@ impl FighterStateImpl for HitstunState {
     }
 
     fn update(&mut self, ctx: &mut UpdateContext) {
+        if !self.knockback_applied {
+            let launch_direction = attack::directional_influence::apply_directional_influence(
+        ctx.input.get_last_frame().movement,
+                self.hit_reaction.launch_angle,
+                ctx.game_settings.fighter_common.di_max_angle
+            );
+
+            ctx.knockback_velocity.0 = launch_direction * self.hit_reaction.launch_velocity;
+            self.knockback_applied = true;
+        }
+
         air::integrate_gravity(ctx.velocity, ctx.fighter_attributes);
 
         let speed = ctx.knockback_velocity.length();
@@ -77,7 +86,6 @@ impl FighterStateImpl for HitstunState {
             HitstopStateKind::Airborne => AnimKind::FlinchAir,
         };
         state_context.play_animation(animation, false);
-        state_context.knockback_velocity.0 = self.hit_reaction.launch_velocity;
     }
 
     fn on_exit(&mut self, _state_context: &mut ExitContext) {}

src/game_settings.rs

@@ -36,6 +36,9 @@ pub struct FighterSettingsCommon {
     pub visual_shake_table: Vec<f32>,
     /// The attacker will always get less hitstop
     pub attacker_visual_shake_multiplier: f32,
+    
+    /// Maximum angle changed caused by directional influence
+    pub di_max_angle: FGi32,
 }
 #[derive(Reflect, Serialize, Deserialize, Clone)]
 #[reflect(opaque)]