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Refactor implementation of e2e collision

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+ Add some hopefully helpful comments
+ Extract colliding tries to separate function
+ Move to Capsule + Cylinder collider combination instead of Capsule +
  Capsule.
This commit is contained in:
juliancoffee 2021-09-16 00:27:48 +03:00
parent 44962958d8
commit eeb3bec8ad
3 changed files with 212 additions and 149 deletions
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6
common/src/comp/phys.rs
View File

@ -54,10 +54,12 @@ pub struct PreviousPhysCache {
/// Calculates a Sphere over the Entity for quick boundary checking
pub collision_boundary: f32,
pub scale: f32,
/// Approximate radius of cylinder of collider.
pub scaled_radius: f32,
/// Radius of stadium of collider.
pub neighborhood_radius: f32,
/// p0 and p1 in case of CapsulePrism collider, Vec2::zero() otherwise.
pub origins: (Vec2<f32>, Vec2<f32>),
/// relative p0 and p1 of collider's statium, None if cylinder.
pub origins: Option<(Vec2<f32>, Vec2<f32>)>,
pub ori: Quaternion<f32>,
}

353
common/systems/src/phys.rs
View File

@ -23,7 +23,7 @@ use specs::{
Entities, Entity, Join, ParJoin, Read, ReadExpect, ReadStorage, SystemData, Write, WriteExpect,
WriteStorage,
};
use std::ops::Range;
use std::ops::{ControlFlow, Range};
use vek::*;
/// The density of the fluid as a function of submersion ratio in given fluid
@ -193,7 +193,7 @@ impl<'a> PhysicsData<'a> {
scale: 0.0,
scaled_radius: 0.0,
neighborhood_radius: 0.0,
origins: (Vec2::zero(), Vec2::zero()),
origins: None,
ori: Quaternion::identity(),
});
}
@ -224,7 +224,9 @@ impl<'a> PhysicsData<'a> {
let flat_radius = collider.map(|c| c.get_radius()).unwrap_or(0.5) * scale;
let neighborhood_radius = match collider {
Some(Collider::CapsulePrism { radius, .. }) => radius * scale,
_ => flat_radius,
Some(Collider::Box { .. } | Collider::Voxel { .. } | Collider::Point) | None => {
flat_radius
},
};
let radius = (flat_radius.powi(2) + half_height.powi(2)).sqrt();
@ -237,31 +239,36 @@ impl<'a> PhysicsData<'a> {
phys_cache.scaled_radius = flat_radius;
let ori = ori.to_quat();
let (p0, p1) = match collider {
let origins = match collider {
Some(Collider::CapsulePrism { p0, p1, .. }) => {
// Build the line between two origins
// Apply orientation to origins of prism.
// We do this by building line between them,
// rotate it and then split back to origins.
//
// (Otherwise we will need to do the same with each
// origin).
let a = p1 - p0;
let len = a.magnitude();
// Make it 3d
let a = Vec3::new(a.x, a.y, 0.0);
// Rotate it
// We cast it to 3d and then convert it back to 2d
// to apply quaternion.
let a = a.with_z(0.0);
let a = ori * a;
// Make it 2d again
let a = Vec2::new(a.x, a.y);
let a = a.xy();
// Previous operation could shrink x and y coordinates
// if orientation had Z parameter.
// Make sure we have the same length as before
// (and scale it)
// (and scale it, while we on it).
let a = a * scale * len / a.magnitude();
// Splite the oriented line into two origins
let p0 = -a / 2.0;
let p1 = a / 2.0;
(p0, p1)
Some((p0, p1))
},
Some(Collider::Box { .. } | Collider::Voxel { .. } | Collider::Point) | None => {
(Vec2::zero(), Vec2::zero())
None
},
};
phys_cache.origins = (p0, p1);
phys_cache.origins = origins;
phys_cache.ori = ori;
}
}
@ -350,7 +357,7 @@ impl<'a> PhysicsData<'a> {
mass,
collider,
sticky,
physics,
mut physics,
projectile,
char_state_maybe,
)| {
@ -443,113 +450,37 @@ impl<'a> PhysicsData<'a> {
for i in 0..increments {
let factor = i as f32 * step_delta;
// get positions
let pos = pos.0 + previous_cache.velocity_dt * factor;
let pos_other =
pos_other.0 + previous_cache_other.velocity_dt * factor;
// Compare Z ranges
let ceiling = pos.z + z_limits.1 * previous_cache.scale;
let floor = pos.z + z_limits.0 * previous_cache.scale;
let ceiling_other =
pos_other.z + z_limits_other.1 * previous_cache_other.scale;
let floor_other =
pos_other.z + z_limits_other.0 * previous_cache_other.scale;
let in_z_range =
ceiling >= floor_other && floor <= ceiling_other;
// check horizontal distance
let (p0_offset, p1_offset) = previous_cache.origins;
let p0 = pos + p0_offset;
let p1 = pos + p1_offset;
let segment = LineSegment2 {
start: p0.xy(),
end: p1.xy(),
};
let (p0_offset_other, p1_offset_other) =
previous_cache_other.origins;
let p0_other = pos_other + p0_offset_other;
let p1_other = pos_other + p1_offset_other;
let segment_other = LineSegment2 {
start: p0_other.xy(),
end: p1_other.xy(),
};
let diff = projection_between(segment, segment_other);
let in_collision_range =
diff.magnitude_squared() <= collision_dist.powi(2);
let collides = in_collision_range && in_z_range;
if !collides {
continue;
}
// If entities have not yet collided
// this tick (but just did) and if entity
//
// is either in mid air
// or is not sticky,
//
// then mark them as colliding with the
// other entity.
if !collision_registered && (is_mid_air || !is_sticky) {
physics.touch_entities.insert(*other);
entity_entity_collisions += 1;
}
// Don't apply e2e pushback to entities
// that are in a forced movement state
// (e.g. roll, leapmelee).
//
// This allows leaps to work properly
// (since you won't get pushed away before
// delivering the hit), and allows
// rolling through an enemy when trapped
// (e.g. with minotaur).
//
// This allows using e2e pushback to
// gain speed by jumping out of a roll
// while in the middle of a collider, this
// is an intentional combat mechanic.
let forced_movement = matches!(
match try_e2e_collision(
// utility variables for our entity
&mut collision_registered,
&mut entity_entity_collisions,
factor,
collision_dist,
&mut physics,
char_state_maybe,
Some(cs) if cs.is_forced_movement());
// Don't apply repulsive force
// to projectiles
//
// or if we're colliding with a
// terrain-like entity,
//
// or if we are a terrain-like entity
//
// Don't apply force when entity
// is a sticky which is on the
// ground (or on the wall)
if !forced_movement
&& (!is_sticky || is_mid_air)
&& diff.magnitude_squared() > 0.0
&& !is_projectile
&& !matches!(collider_other, Some(Collider::Voxel { .. }))
&& !matches!(collider, Some(Collider::Voxel { .. }))
{
let force = 400.0
* (collision_dist - diff.magnitude())
* mass_other.0
/ (mass.0 + mass_other.0);
vel_delta +=
Vec3::from(diff.normalized()) * force * step_delta;
&mut vel_delta,
step_delta,
// physics flags
is_mid_air,
is_sticky,
is_projectile,
// entity we colliding with
*other,
// symetrical collider context
pos,
pos_other,
previous_cache,
previous_cache_other,
z_limits,
z_limits_other,
collider,
collider_other,
*mass,
*mass_other,
) {
ControlFlow::Continue(..) => continue,
ControlFlow::Break(..) => break,
}
collision_registered = true;
}
},
);
@ -1861,31 +1792,161 @@ fn voxel_collider_bounding_sphere(
}
}
/// Get the shortest line segment between AB and CD, used for pushback
/// and collision checks.
fn projection_between(ab: LineSegment2<f32>, cd: LineSegment2<f32>) -> Vec2<f32> {
// On 2d we can just check projection of A to CD, B to CD, C to AB and D to AB.
#[allow(clippy::too_many_arguments)]
fn try_e2e_collision(
// utility variables for our entity
collision_registered: &mut bool,
entity_entity_collisions: &mut u64,
factor: f32,
collision_dist: f32,
physics: &mut PhysicsState,
char_state_maybe: Option<&CharacterState>,
vel_delta: &mut Vec3<f32>,
step_delta: f32,
// physics flags
is_mid_air: bool,
is_sticky: bool,
is_projectile: bool,
// entity we colliding with
other: Uid,
// symetrical collider context
pos: &Pos,
pos_other: &Pos,
previous_cache: &PreviousPhysCache,
previous_cache_other: &PreviousPhysCache,
z_limits: (f32, f32),
z_limits_other: (f32, f32),
collider: Option<&Collider>,
collider_other: Option<&Collider>,
mass: Mass,
mass_other: Mass,
) -> ControlFlow<()> {
// Find the distance betwen our collider and
// collider we collide with and get vector of pushback.
//
// NOTE: We don't check if segments are intersecting, because
// even if they do, we still need to return pushback vector.
let a = ab.start;
let b = ab.end;
let c = cd.start;
let d = cd.end;
// If we aren't colliding, just skip step.
let projections = [
// A to CD
a - cd.projected_point(a),
// B to CD
b - cd.projected_point(b),
// C to AB
c - ab.projected_point(c),
// D to AB
d - ab.projected_point(d),
];
// Get positions
let pos = pos.0 + previous_cache.velocity_dt * factor;
let pos_other = pos_other.0 + previous_cache_other.velocity_dt * factor;
// min_by_key returns None only if iterator is empty, so unwrap is fine
IntoIterator::into_iter(projections)
.min_by_key(|p| ordered_float::OrderedFloat(p.magnitude_squared()))
.unwrap()
// Compare Z ranges
let ceiling = pos.z + z_limits.1 * previous_cache.scale;
let floor = pos.z + z_limits.0 * previous_cache.scale;
let ceiling_other = pos_other.z + z_limits_other.1 * previous_cache_other.scale;
let floor_other = pos_other.z + z_limits_other.0 * previous_cache_other.scale;
let in_z_range = ceiling >= floor_other && floor <= ceiling_other;
// Check horizontal distance.
let diff = if in_z_range {
let ours = ColliderContext {
pos,
previous_cache,
};
let theirs = ColliderContext {
pos: pos_other,
previous_cache: previous_cache_other,
};
projection_between(ours, theirs)
} else {
return ControlFlow::Continue(());
};
let in_collision_range = diff.magnitude_squared() <= collision_dist.powi(2);
if !in_collision_range {
return ControlFlow::Continue(());
}
// If entities have not yet collided this tick (but just did) and if entity
// is either in mid air or is not sticky, then mark them as colliding with
// the other entity.
if !*collision_registered && (is_mid_air || !is_sticky) {
physics.touch_entities.insert(other);
*entity_entity_collisions += 1;
}
// Don't apply e2e pushback to entities that are in a forced movement state
// (e.g. roll, leapmelee).
//
// This allows leaps to work properly (since you won't get pushed away
// before delivering the hit), and allows rolling through an enemy when
// trapped (e.g. with minotaur).
//
// This allows using e2e pushback to gain speed by jumping out of a roll
// while in the middle of a collider, this is an intentional combat mechanic.
let forced_movement = matches!(char_state_maybe, Some(cs) if cs.is_forced_movement());
// Don't apply repulsive force to projectiles,
// or if we're colliding with a terrain-like entity,
// or if we are a terrain-like entity.
//
// Don't apply force when entity is a sticky which is on the ground
// (or on the wall).
if !forced_movement
&& (!is_sticky || is_mid_air)
&& diff.magnitude_squared() > 0.0
&& !is_projectile
&& !matches!(collider_other, Some(Collider::Voxel { .. }))
&& !matches!(collider, Some(Collider::Voxel { .. }))
{
let force =
400.0 * (collision_dist - diff.magnitude()) * mass_other.0 / (mass.0 + mass_other.0);
*vel_delta += Vec3::from(diff.normalized()) * force * step_delta;
}
*collision_registered = true;
ControlFlow::Continue(())
}
struct ColliderContext<'a> {
pos: Vec3<f32>,
previous_cache: &'a PreviousPhysCache,
}
/// Find pushback vector
fn projection_between(c0: ColliderContext, c1: ColliderContext) -> Vec2<f32> {
// "Proper" way to do this would be handle the case when both our colliders
// are capsule prisms by building origins from p0, p1 offsets and our
// positions and find some sort of projection between line segments of
// both colliders.
// While it's possible, it's not a trivial operation especially
// in the case when they are intersect. Because in such case,
// even when you found intersection and you should push entities back
// from each other, you get then difference between them is 0 vector.
//
// Considering that we won't fully simulate collision of capsule prism.
// As intermediate solution, we would assume that bigger collider
// (with bigger scaled_radius) is capsule prism (cylinder is special
// case of capsule prism too) and smaller collider is cylinder (point is
// special case of cylinder).
if c0.previous_cache.scaled_radius > c1.previous_cache.scaled_radius {
let (p0_offset, p1_offset) = c0
.previous_cache
.origins
.unwrap_or((Vec2::zero(), Vec2::zero()));
let segment = LineSegment2 {
start: c0.pos.xy() + p0_offset,
end: c0.pos.xy() + p1_offset,
};
let other = c1.pos.xy();
other - segment.projected_point(other)
} else {
let we = c0.pos.xy();
let (p0_offset_other, p1_offset_other) = c1
.previous_cache
.origins
.unwrap_or((Vec2::zero(), Vec2::zero()));
let segment_other = LineSegment2 {
start: c1.pos.xy() + p0_offset_other,
end: c1.pos.xy() + p1_offset_other,
};
we - segment_other.projected_point(we)
}
}

2
server/src/state_ext.rs
View File

@ -216,7 +216,7 @@ impl StateExt for State {
z_min: 0.0,
z_max: body.height(),
}
}
},
})
.with(comp::Controller::default())
.with(body)