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| -rw-r--r-- | Makefile.am | 1 | ||||
| -rw-r--r-- | sly/transition.scm | 164 |
2 files changed, 165 insertions, 0 deletions
diff --git a/Makefile.am b/Makefile.am index 8ed383a..59c89c0 100644 --- a/Makefile.am +++ b/Makefile.am @@ -44,6 +44,7 @@ SOURCES = \ sly/texture.scm \ sly/tileset.scm \ sly/transform.scm \ + sly/transition.scm \ sly/vector.scm \ sly/window.scm \ $(WRAPPER_SOURCES) diff --git a/sly/transition.scm b/sly/transition.scm new file mode 100644 index 0000000..f813828 --- /dev/null +++ b/sly/transition.scm @@ -0,0 +1,164 @@ +;;; Sly +;;; Copyright (C) 2014 David Thompson <davet@gnu.org> +;;; +;;; Sly is free software: you can redistribute it and/or modify it +;;; under the terms of the GNU General Public License as published by +;;; the Free Software Foundation, either version 3 of the License, or +;;; (at your option) any later version. +;;; +;;; Sly is distributed in the hope that it will be useful, but WITHOUT +;;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +;;; or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public +;;; License for more details. +;;; +;;; You should have received a copy of the GNU General Public License +;;; along with this program. If not, see +;;; <http://www.gnu.org/licenses/>. + +;;; Commentary: +;; +;; Interpolate values over time with easing. Useful for animation. +;; +;;; Code: + +(define-module (sly transition) + #:use-module (sly agenda) + #:use-module (sly color) + #:use-module (sly coroutine) + #:use-module (sly math) + #:use-module (sly signal) + #:use-module (sly vector) + #:export (ease-linear + ease-in-sine ease-out-sine ease-in-out-sine + ease-in-quad ease-out-quad ease-in-out-quad + interpolator + number-interpolate vector-interpolate color-interpolate + transition)) + +;;; +;;; Easings +;;; + +(define (ease-linear t d) + (/ t d)) + +(define (ease-in-sine t d) + (let ((delta (/ t d))) + (+ (* (- delta) (cos (* delta pi/2))) delta))) + +(define (ease-out-sine t d) + (let ((delta (/ t d))) + (* delta (sin (* delta pi/2))))) + +(define (ease-in-out-sine t d) + (* (/ t d -2) + (1- (cos (/ (* t pi) d))))) + +(define (ease-in-quad t d) + (expt (/ t d) 3)) + +(define (ease-out-quad t d) + (let ((delta (/ t d))) + (* (- delta) delta (- delta 2)))) + +(define (ease-in-out-quad t d) + (let ((delta (/ t d)) + (t (/ t (/ d 2)))) + (if (< t 1) + (* (/ delta 2) t t) + (* (/ delta -2) + (1- (* (1- t) (- t 3))))))) + +;; TODO: See +;; <http://gsgd.co.uk/sandbox/jquery/easing/jquery.easing.1.3.js> for +;; implementation details. +;; +;; ease-in-cubic +;; ease-out-cubic +;; ease-in-out-cubic +;; ease-in-quart +;; ease-out-quart +;; ease-in-out-quart +;; ease-in-quint +;; ease-out-quint +;; ease-in-out-quint +;; ease-in-expo +;; ease-out-expo +;; ease-in-out-expo +;; ease-in-circ +;; ease-out-circ +;; ease-in-out-circ +;; ease-in-back +;; ease-out-back +;; ease-in-out-back +;; ease-in-elastic +;; ease-out-elastic +;; ease-in-out-elastic +;; ease-in-bounce +;; ease-out-bounce +;; ease-in-out-bounce + +;;; +;;; Interpolators +;;; + +(define (interpolator + *) + "Return a new procedure that accepts three arguments: a, b, and +delta. The returned procedure uses the operations + and * to +interpolate a value between a and b. Delta should always be in the +range [0, 1]." + (lambda (a b delta) + (+ (* a (- 1 delta)) + (* b delta)))) + +(define number-interpolate (interpolator + *)) +(define vector-interpolate (interpolator v+ v*)) +(define color-interpolate (interpolator color+ color-scale)) + +(define (guess-interpolator a b) + (define (both? pred) + (and (pred a) (pred b))) + + (cond ((both? number?) + number-interpolate) + ((both? vector?) + vector-interpolate) + ((both? color?) + color-interpolate) + (else + (error "Failed to guess interpolator: " a b)))) + +;;; +;;; Transitions +;;; + +(define* (transition start end duration + #:optional #:key + (interpolator #f) + (ease ease-linear) + (step 1)) + "Return a signal that transitions from START to END in DURATION +ticks. The INTERPOLATOR procedure is used to compute intermediate +values. When no interpolator is specified, it is inferred. +Interpolation procedures can be inferred for numbers, vectors, and +colors. For other values, an error is thrown unless INTERPOLATOR is +passed explicitly. EASE specifies the easing procedure to apply to +the transition. Linear easing is used by default. STEP specifies the +number of ticks between each interpolation sample. By default, a step +of 1 is used for the smoothest, but most computationally expensive +transition." + (let ((interpolator (or interpolator + (guess-interpolator start end)))) + (define (value-at t) + (interpolator start end (ease t duration))) + + (let ((signal (make-signal start))) + (coroutine + (let lp ((t 0)) + (if (< t duration) + (begin + (wait (min step (- duration t))) + (signal-set! signal (value-at t)) + (lp (+ t step))) + (signal-set! signal end)))) + signal))) |