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;;;; easing.lisp
(in-package #:animise)
;;; Utilities for defining easing functions
(defun time-frac (start duration current)
(let* ((end (+ start duration))
(progress (max 0 (- end current))))
(- 1.0 (/ progress duration))))
(defmacro def-ease (name &rest body)
`(defun ,name (start duration current &optional (delta 1))
(let ((frac (time-frac start duration current)))
,@body)))
(defmacro def-mirror-for (name-of-ease)
(let ((mirror-name (read-from-string (format nil "mirror-~a" name-of-ease))))
`(def-ease ,mirror-name
(if (<= frac 0.5)
(,name-of-ease start (* 0.5 duration) current delta)
(,name-of-ease start (* 0.5 duration)
(- (+ start (* 0.5 duration))
(- current (+ start (* 0.5 duration))))
delta)))))
;;; EASING FUNCTION DEFINITIONS ;;;
;;; The DEF-EASE macro defines a function. the BODY of the function has the
;;; following variables available to it:
;;; START the start time in MS
;;; DURATION intended duration of this animation
;;; CURRENT the current time, sometime after START
;;; DELTA, a number, the total change in the value being animated (e.g. X coordinate)
;;; FRAC, a number between 0 and 1, the how close to completion this animation is.
(def-ease linear (* delta frac))
(def-mirror-for linear)
(def-ease quad-in (* frac frac delta))
(def-mirror-for quad-in)
(def-ease quad-out (* frac (- frac 2.0) -1 delta))
(def-mirror-for quad-out)
(def-ease quad-in-out
(setf frac (/ frac 0.5))
(if (< frac 1) (* frac frac 0.5 delta)
(progn (decf frac)
(* -1 delta 0.5 (1- (* frac (- frac 2)))))))
(def-mirror-for quad-in-out)
(def-ease cubic-in (* frac frac frac delta))
(def-mirror-for cubic-in)
(def-ease cubic-out
(decf frac)
(* (1+ (* frac frac frac)) delta))
(def-mirror-for cubic-out)
(def-ease cubic-in-out
(setf frac (/ frac 0.5))
(if (< frac 1) (* delta 0.5 frac frac frac)
(progn
(decf frac 2)
(* delta 0.5 (+ 2 (* frac frac frac))))))
(def-mirror-for cubic-in-out)
(def-ease sinusoidal-in
(+ delta (* -1 delta (cos (* frac pi 0.5)))))
(def-mirror-for sinusoidal-in)
(def-ease sinusoidal-out
(* delta (sin (* frac pi 0.5))))
(def-mirror-for sinusoidal-out)
(def-ease sinusoidal-in-out
(* delta -0.5 (1- (cos (* pi frac)))))
(def-mirror-for sinusoidal-in-out)
(def-ease elastic-out
(let ((sqrd (* frac frac))
(cubed (* frac frac frac)))
(* 100 delta (+ (* 0.33 sqrd cubed)
(* -1.06 sqrd sqrd)
(* 1.26 cubed)
(* -0.67 sqrd)
(* 0.15 frac)))))
(def-mirror-for elastic-out)
(def-ease bounce-out
(let ((coeff 7.5627)
(step (/ 1 2.75)))
(cond ((< frac step)
(* delta coeff frac frac))
((< frac (* 2 step))
(decf frac (* 1.5 step))
(* delta
(+ 0.75
(* coeff frac frac))))
((< frac ( * 2.5 step))
(decf frac (* 2.25 step))
(* delta
(+ 0.9375
(* coeff frac frac))))
(t
(decf frac (* 2.65 step))
(* delta
(+ 0.984375
(* coeff frac frac)))))))
(def-mirror-for bounce-out)
;;; Some functions to check your intuitions about the output of easing functions
(defun make-frames (ease-fn &optional (step 0.1))
(loop :for time :from 0 :upto (+ 1 step) :by step
:collect (funcall ease-fn 0 1.0 time)))
(defun print-frames (fn &key (width 20) (mark #\.) (step 0.1))
(loop for frame in (make-frames fn step) do
(dotimes (x width) (princ #\Space))
(dotimes (x (round (* frame width)))
(princ #\Space))
(princ mark)
(terpri)))
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