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use std::time::Duration;
use crate::math::{AdjustPrecision, AsF32, Float, Vector3};
use bevy::prelude::*;
/// An indication that a character was knocked back and "struggles" to get back to its original
/// velocity.
#[derive(Clone, Debug)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
pub struct VelocityBoundary {
base: Float,
original_frontier: Float,
frontier: Float,
pub direction: Dir3,
no_push_timer: Timer,
}
impl VelocityBoundary {
pub fn new(
disruption_from: Vector3,
disruption_to: Vector3,
no_push_timeout: f32,
) -> Option<Self> {
let Ok(disruption_direction) = Dir3::new((disruption_to - disruption_from).f32()) else {
return None;
};
let frontier = disruption_to.dot(disruption_direction.adjust_precision());
Some(Self {
base: disruption_from.dot(disruption_direction.adjust_precision()),
original_frontier: frontier,
frontier,
direction: disruption_direction,
no_push_timer: Timer::from_seconds(no_push_timeout, TimerMode::Once),
})
}
/// Call this every frame to update the velocity boundary.
///
/// This methos takes care of "clearing" the boundary when it gets "pushed" (the character's
/// actual velocity goes past the boundary).
///
/// This method does not detect when the boundary is cleared - use
/// [`is_cleared`](Self::is_cleared) for that purpose
///
/// This method does not apply the boundary - it only updates it. To apply the boundary, use
/// [`calc_boost_part_on_boundary_axis_after_limit`](Self::calc_boost_part_on_boundary_axis_after_limit)
/// to determine how to alter the acceleration.
///
/// # Arguments:
///
/// * `velocity` - the velocity as reported by the physics backend. This is the data tracked in
/// the [`TnuaRigidBodyTracker`](crate::TnuaRigidBodyTracker), so a typical basis or action
/// will get it from [`TnuaBasisContext::tracker`](crate::TnuaBasisContext::tracker).
/// * `frame_duration` - the duration of the current frame, in seconds.
pub fn update(&mut self, velocity: Vector3, frame_duration: Duration) {
let new_frontier = velocity.dot(self.direction.adjust_precision());
if new_frontier < self.frontier {
self.frontier = new_frontier;
self.no_push_timer.reset();
} else {
self.no_push_timer.tick(frame_duration);
}
}
pub fn is_cleared(&self) -> bool {
self.no_push_timer.is_finished() || self.frontier <= self.base
}
/// Calculate how a boost needs to be adjusted according to the boundary.
///
/// Note that the returned value is the boost limit only on the axis of the returned direction.
/// The other axes should remain the same (unless the caller has a good reason to modify them).
/// The reason why this method doesn't simply return the final boost is that the caller may be
/// using [`TnuaVelChange`](crate::TnuaVelChange) which combines acceleration and impulse, and
/// if so then it is the caller's responsibility to amend the result of this method to match
/// that scheme.
///
/// # Arguments:
///
/// * `current_velocity` - the velocity of the character **before the boost**.
/// * `regular_boost` - the boost that the caller would have applied to the character before
/// taking the boundary into account.
/// * `boost_limit_inside_barrier` - the maximum boost allowed inside a fully strength barrier,
/// assuming it goes directly against the direction of the boundary.
/// * `barrier_strength_diminishing` - an exponent describing how the boundary strength
/// diminishes when the barrier gets cleared. For best results, set it to values larger than
/// 1.0.
pub fn calc_boost_part_on_boundary_axis_after_limit(
&self,
current_velocity: Vector3,
regular_boost: Vector3,
boost_limit_inside_barrier: Float,
barrier_strength_diminishing: Float,
) -> Option<(Dir3, Float)> {
let boost = regular_boost.dot(self.direction.adjust_precision());
if 0.0 <= boost {
// Not pushing the barrier
return None;
}
let current = current_velocity.dot(self.direction.adjust_precision());
let after_boost = current + boost;
if self.frontier <= after_boost {
return None;
}
let boost_before_barrier = (current - self.frontier).max(0.0);
let fraction_before_frontier = boost_before_barrier / -boost;
let fraction_after_frontier = 1.0 - fraction_before_frontier;
let push_inside_barrier = fraction_after_frontier * boost_limit_inside_barrier;
let barrier_depth = self.frontier - self.base;
if barrier_depth <= 0.0 {
return None;
}
let fraction_inside_barrier = if push_inside_barrier <= barrier_depth {
fraction_after_frontier
} else {
barrier_depth / boost_limit_inside_barrier
}
.clamp(0.0, 1.0);
let boost_outside_barrier = (1.0 - fraction_inside_barrier) * boost;
// Make it negative here, because this is the one that pushes against the barrier
let boost_inside_barrier = fraction_inside_barrier * -boost_limit_inside_barrier;
let total_boost = boost_outside_barrier + boost_inside_barrier;
let barrier_strength = self.percentage_left().powf(barrier_strength_diminishing);
let total_boost = (1.0 - barrier_strength) * boost + barrier_strength * total_boost;
Some((-self.direction, -total_boost))
}
fn percentage_left(&self) -> Float {
let current_depth = self.frontier - self.base;
let original_depth = self.original_frontier - self.base;
current_depth / original_depth
}
}