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physics.lisp
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211 lines (200 loc) · 11.3 KB
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(uiop:define-package #:slither/physics
(:use #:cl
#:slither/utils
#:slither/behaviors
#:slither/core
#:slither/scenes
#:org.shirakumo.fraf.math.vectors)
(:export :circle-collider
:circle-collision-p
:rigidbody
:rigidbody-position
:rigidbody-mass
:rigidbody-velocity
:rigidbody-drag
:rigidbody-velocity+
:point-collides-p
:circle-overlaps-point-p
:circle-collisions
:inverse-mass))
(in-package #:slither/physics)
(-> circle-collision-p (vec2 float vec2 float) boolean)
(defun circle-collision-p (circle1-position circle1-radius
circle2-position circle2-radius)
(< (vlength (v- circle1-position circle2-position))
(+ circle1-radius circle2-radius)))
(defun circle-overlaps-point-p (circle-position circle-radius point)
(< (vlength (v- point circle-position))
circle-radius))
(defun circle-collides-p (circle-position circle-radius)
(loop for circle-collider in (behaviors-of-type 'circle-collider)
do (when (circle-collision-p circle-position
circle-radius
(rigidbody-position (behavior-entity circle-collider))
(circle-radius circle-collider))
(return circle-collider))))
(defun circle-collisions (circle-position circle-radius)
(loop for circle-collider in (behaviors-of-type 'circle-collider)
when (circle-collision-p circle-position
circle-radius
(rigidbody-position (behavior-entity circle-collider))
(circle-radius circle-collider))
collect circle-collider))
(defun point-collides-p (point)
(loop for circle-collider in (behaviors-of-type 'circle-collider)
do (when (circle-overlaps-point-p (rigidbody-position (behavior-entity circle-collider))
(circle-radius circle-collider)
point)
(return circle-collider))))
(defbehavior circle-collider
()
(:circle-radius (&optional (circle *behavior*))
(vx (transform-size circle)))
(:circle-collider-collision-p (circle)
(with-behaviors ((() (circle1-collider circle-collider))
(((circle1-position position)) (circle1-transform transform))) circle
(with-behaviors ((((circle2-position position)) (circle2-transform transform))) *entity*
(circle-collision-p circle1-position (circle-radius circle1-collider)
circle2-position (circle-radius *behavior*))))))
(defun inverse-mass (mass)
(if (= mass 0.0)
0.0
(/ 1 mass)))
(defbehavior rigidbody
((colliders :init (list))
(mass :init 1.0)
(bounciness :init 0.0)
(drag :init 0.0)
(velocity :init (vec2)
:networked t)
(position :init (vec2)
:networked t)
(previous-position :init (vec2)))
(:networked t)
(:required-behaviors
transform)
(:start
(when-let ((collider (entity-find-behavior *entity* 'circle-collider)))
(setf (rigidbody-colliders)
(list collider)))
(setf (rigidbody-position) (transform-position))
(setf (rigidbody-previous-position) (transform-position)))
(:tick
(setf (transform-position)
(vlerp (rigidbody-previous-position)
(rigidbody-position)
(interpolation-alpha))))
(:fixed-tick
(setf (rigidbody-previous-position)
(rigidbody-position))
;; Drag
(vdecf (rigidbody-velocity)
(v* (rigidbody-velocity)
(vabs (rigidbody-velocity))
(- (rigidbody-drag))
(delta-time)))
;; Collisions
(loop for this-collider in (rigidbody-colliders)
do (loop for foreign-collider in
;; Make sure the collision check doesn't run on a collider on current entity
(remove-if-not
(lambda (behavior)
(not (eql (behavior-entity behavior) *entity*)))
(behaviors-of-type 'circle-collider))
;; TODO: Add etypecase for other colliders
do (let* ((offset (v- (rigidbody-position (behavior-entity foreign-collider))
(rigidbody-position)))
(distance (vlength offset))
(total-size (+ (circle-radius this-collider)
(circle-radius foreign-collider))))
;; Collision detection
(when (< distance total-size)
;; Collision resolution
(let* ((penetration-depth (- total-size distance))
(normalized-offset (if (= (vlength offset) 0)
(vec2 0 1)
(v/ offset distance)))
(this-mass (rigidbody-mass))
(foreign-rigidbody (entity-find-behavior (behavior-entity foreign-collider)
'rigidbody))
(foreign-mass (if foreign-rigidbody
(rigidbody-mass foreign-rigidbody)
0.0)))
(unless (= 0 (+ this-mass foreign-mass))
(let* ((this-inverse-mass (inverse-mass this-mass))
(this-bounciness (rigidbody-bounciness))
(foreign-bounciness (if foreign-rigidbody
(rigidbody-bounciness foreign-rigidbody)
0.0))
(foreign-inverse-mass (inverse-mass foreign-mass))
(foreign-velocity (if foreign-rigidbody
(rigidbody-velocity foreign-rigidbody)
(vec2)))
(static-friction 0.1)
(dynamic-friction 1.0)
(relative-velocity (v- foreign-velocity
(rigidbody-velocity)))
(velocity-along-normal (v. relative-velocity
normalized-offset))
(restitution (min this-bounciness foreign-bounciness))
(normal-impulse (/ (* (- (+ 1 restitution)) velocity-along-normal)
(+ this-inverse-mass
foreign-inverse-mass))))
;; Positional correction
(let* ((percent 0.2)
(slop 0.01)
(correction
(v* normalized-offset
(* (/ (max (- penetration-depth slop) 0.0) (+ this-inverse-mass
foreign-inverse-mass))
percent))))
(nv- (rigidbody-position)
(v* correction this-inverse-mass))
(nv+ (rigidbody-position foreign-rigidbody)
(v* correction foreign-inverse-mass)))
;; Don't resolve unless the colliders are moving towards each other
(unless (> velocity-along-normal 0)
;; Collision impulse resolution
(setf (rigidbody-velocity)
(v- (rigidbody-velocity)
(v* normalized-offset
normal-impulse
this-inverse-mass)))
(when foreign-rigidbody
(setf (rigidbody-velocity foreign-rigidbody)
(v+ (rigidbody-velocity foreign-rigidbody)
(v* normalized-offset
normal-impulse
foreign-inverse-mass))))
(let* ((relative-velocity (v- (if foreign-rigidbody
(rigidbody-velocity foreign-rigidbody)
(vec2))
(rigidbody-velocity)))
(tangent (safe-vscale
(v- relative-velocity
(v* normalized-offset
(v. relative-velocity normalized-offset)))
1))
(tangent-magnitude (/ (- (v. relative-velocity tangent))
(+ this-inverse-mass
foreign-inverse-mass)))
(mu (sqrt (+ (expt static-friction 2) (expt static-friction 2))))
(friction-impulse (if (< (abs tangent-magnitude) (* normal-impulse mu))
(v* tangent tangent-magnitude)
(let ((dynamic-friction (sqrt (+ (expt dynamic-friction 2)
(expt dynamic-friction 2)))))
(v* tangent (- (min (* normal-impulse dynamic-friction)
(abs tangent-magnitude))))))))
;; Friction impulse resolution
(setf (rigidbody-velocity)
(v- (rigidbody-velocity)
(v* friction-impulse this-inverse-mass)))
(when foreign-rigidbody
(setf (rigidbody-velocity foreign-rigidbody)
(v+ (rigidbody-velocity foreign-rigidbody)
(v* friction-impulse foreign-inverse-mass)))))))))))))
;; Update position
(setf (rigidbody-position)
(v+ (rigidbody-position) (rigidbody-velocity))))
(:rigidbody-velocity+ (force)
(setf (rigidbody-velocity) (nv+ (rigidbody-velocity) force))))