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;;
;; starlet/effects.scm
;;
;; Copyright © 2020-2021 Thomas White <taw@bitwiz.org.uk>
;;
;; This file is part of Starlet.
;;
;; Starlet 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.
;;
;; This program 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/>.
;;
(define-module (starlet effects)
#:use-module (starlet clock)
#:use-module (starlet state)
#:use-module (starlet attributes)
#:export (flash
sinewave
flash-chase))
(define pi (* 2 (acos 0)))
(define (square-wave time hz)
(if (> (sin (* 2 pi hz time))
0)
100
0))
(define (flash hz)
(let ((clock (make-clock)))
(lambda ()
(square-wave (elapsed-time clock)
hz))))
(define (sinewave hz range-min range-max)
(let ((clock (make-clock)))
(lambda ()
(+ range-min
(* (/ (- range-max range-min) 2)
(+ 1 (sin (* 2 pi hz (elapsed-time clock)))))))))
(define (hump t on-time)
(cond
((< t 0.0) 0.0)
((> t on-time) 0.0)
(else (* 100 (sin (* pi (/ t on-time)))))))
(define* (flash-chase group
#:key (repeat-time 2) (offset-time 0.3) (on-time 0.5))
(let ((clock (make-clock)))
(for-each
(lambda (fix idx)
(at fix intensity
(lambda ()
(hump (- (euclidean-remainder (elapsed-time clock)
repeat-time)
(* idx offset-time))
on-time))))
group
(iota (length group)))))
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