diff options
| -rw-r--r-- | Makefile.am | 1 | ||||
| -rw-r--r-- | chickadee/math/bezier.scm | 82 |
2 files changed, 83 insertions, 0 deletions
diff --git a/Makefile.am b/Makefile.am index 10b5e6c..4640581 100644 --- a/Makefile.am +++ b/Makefile.am @@ -47,6 +47,7 @@ SOURCES = \ chickadee/queue.scm \ chickadee/math.scm \ chickadee/math/vector.scm \ + chickadee/math/bezier.scm \ chickadee/math/matrix.scm \ chickadee/math/quaternion.scm \ chickadee/math/rect.scm \ diff --git a/chickadee/math/bezier.scm b/chickadee/math/bezier.scm new file mode 100644 index 0000000..e3dfbba --- /dev/null +++ b/chickadee/math/bezier.scm @@ -0,0 +1,82 @@ +;;; Chickadee Game Toolkit +;;; Copyright © 2018 David Thompson <davet@gnu.org> +;;; +;;; Chickadee 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. +;;; +;;; Chickadee 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: +;; +;; Cubic Bezier curves in 2D space. +;; +;;; Code: + +(define-module (chickadee math bezier) + #:use-module (ice-9 match) + #:use-module (srfi srfi-9) + #:use-module (chickadee math vector) + #:export (make-bezier-curve + bezier-curve? + bezier-curve-p0 + bezier-curve-p1 + bezier-curve-p2 + bezier-curve-p3 + bezier-curve-point-at! + bezier-curve-point-at + bezier-path)) + +(define-record-type <bezier-curve> + (make-bezier-curve p0 p1 p2 p3) + bezier-curve? + (p0 bezier-curve-p0) + (p1 bezier-curve-p1) + (p2 bezier-curve-p2) + (p3 bezier-curve-p3)) + +(define (bezier-curve-point-at! dest bezier t) + "Write the coordinates for BEZIER at T (a value in the range [0, 1]) +to the 2D vector DEST." + (let* ((u (- 1.0 t)) + (tt (* t t)) + (uu (* u u)) + (uuu (* uu u)) + (ttt (* tt t)) + (p0 (bezier-curve-p0 bezier)) + (p1 (bezier-curve-p1 bezier)) + (p2 (bezier-curve-p2 bezier)) + (p3 (bezier-curve-p3 bezier))) + (set-vec2-x! dest (+ (* uuu (vec2-x p0)) + (* 3 uu t (vec2-x p1)) + (* 3 u tt (vec2-x p2)) + (* ttt (vec2-x p3)))) + (set-vec2-y! dest (+ (* uuu (vec2-y p0)) + (* 3 uu t (vec2-y p1)) + (* 3 u tt (vec2-y p2)) + (* ttt (vec2-y p3)))))) + +(define (bezier-curve-point-at bezier t) + "Return the coordinates for BEZIER at T (a value in the range [0, +1]) as a 2D vector." + (let ((v #v(0.0 0.0))) + (bezier-curve-point-at! v bezier t) + v)) + +(define (bezier-path . control-points) + "Return a list of connected bezier curves defined by CONTROL-POINTS. +The first curve is defined by the first 4 arguments and every +additional curve thereafter requires 3 additional arguments." + (match control-points + ((_) '()) + ((p0 p1 p2 p3 . prest) + (cons (make-bezier-curve p0 p1 p2 p3) + (apply bezier-path p3 prest))))) |