src/particles.lisp @ 69f98eb3a1df

(in-package #:coding-math.particles)

(defclass particle ()
  ((pos :type 'vec
        :initarg :pos
        :accessor particle-pos)
   (vel :type 'vec
        :initarg :vel
        :accessor particle-vel)
   (grv :type 'vec
        :initarg :grv
        :accessor particle-grv)
   (radius :type 'integer
           :initarg :rad
           :initform 1
           :accessor particle-radius)
   (friction :type 'real
             :initarg :friction
             :initform 0.0
             :accessor particle-friction)
   (mass :type 'real
         :initarg :mass
         :initform 1.0
         :accessor particle-mass)))


(defun make-particle
    (x y
     &key
     (speed 0)
     (direction 0)
     (mass 1.0)
     (radius 1)
     (gravity 0.0)
     (friction 0.0))
  (make-instance 'particle
                 :pos (make-vec x y)
                 :vel (make-vec-md speed direction)
                 :grv (make-vec-md gravity (/ tau 4))
                 :friction friction
                 :mass mass
                 :rad radius))


(defun particle-x (particle)
  (vec-x (particle-pos particle)))

(defun particle-y (particle)
  (vec-y (particle-pos particle)))

(defun particle-wrap! (particle width height)
  (with-slots (radius) particle
    (setf (particle-x particle)
          (wrap-range (- radius)
                      (+ radius width)
                      (particle-x particle))
          (particle-y particle)
          (wrap-range (- radius)
                      (+ radius height)
                      (particle-y particle)))))


(defun (setf particle-x) (new-value particle)
  (setf (vec-x (particle-pos particle)) new-value))

(defun (setf particle-y) (new-value particle)
  (setf (vec-y (particle-pos particle)) new-value))


(defun particle-update! (particle)
  (with-accessors ((pos particle-pos)
                   (vel particle-vel)
                   (grv particle-grv)
                   (friction particle-friction))
      particle
    (vec-add! pos vel)
    (vec-add! vel grv)
    (vec-mul! vel (- 1 friction))))


(defun particle-accelerate! (particle acceleration)
  (vec-add! (particle-vel particle)
            acceleration))


(defun particle-angle-to (particle other-particle)
  (let ((distance (vec-sub (particle-pos other-particle)
                           (particle-pos particle))))
    (atan (vec-y distance)
          (vec-x distance))))

(defun particle-distance-to (particle other-particle)
  (vec-magnitude (vec-sub (particle-pos particle)
                          (particle-pos other-particle))))


(defun particle-gravitate-to! (particle attractor-particle)
  (let ((gravity (make-vec))
        (distance (particle-distance-to particle attractor-particle)))
    (setf (vec-magnitude gravity)
          (/ (particle-mass attractor-particle)
             (* distance distance))
          (vec-angle gravity)
          (particle-angle-to particle attractor-particle))
    (particle-accelerate! particle gravity)))