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-rw-r--r--Makefile.am1
-rw-r--r--chickadee/math/easings.scm104
-rw-r--r--chickadee/scripting.scm27
-rw-r--r--doc/api.texi87
4 files changed, 212 insertions, 7 deletions
diff --git a/Makefile.am b/Makefile.am
index 82c6f83..50b8159 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -51,6 +51,7 @@ SOURCES = \
chickadee/math/vector.scm \
chickadee/math/matrix.scm \
chickadee/math/rect.scm \
+ chickadee/math/easings.scm \
chickadee/color.scm \
chickadee/render/gl.scm \
chickadee/render/gpu.scm \
diff --git a/chickadee/math/easings.scm b/chickadee/math/easings.scm
new file mode 100644
index 0000000..115c2bb
--- /dev/null
+++ b/chickadee/math/easings.scm
@@ -0,0 +1,104 @@
+;;; Chickadee Game Toolkit
+;;; Copyright © 2017 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/>.
+
+(define-module (chickadee math easings)
+ #:use-module (chickadee math)
+ #:export (linear
+ smoothstep
+ ease-in-quad
+ ease-out-quad
+ ease-in-out-quad
+ 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-sine
+ ease-out-sine
+ ease-in-out-sine))
+
+(define-inlinable (linear t)
+ t)
+
+(define-inlinable (smoothstep t)
+ (* t t (- 3 (* 2 t))))
+
+(define-inlinable (ease-in-quad t)
+ (* t t))
+
+(define-inlinable (ease-out-quad t)
+ (* t (- 2.0 t)))
+
+(define-inlinable (ease-in-out-quad t)
+ (if (< t 0.5)
+ (* 2.0 t t)
+ (- (* (- 4 (* 2.0 t)) t) 1.0)))
+
+(define-inlinable (ease-in-cubic t)
+ (* t t t))
+
+(define-inlinable (ease-out-cubic t)
+ (let ((t* (- t 1.0)))
+ (+ 1.0 (* t* t* t*))))
+
+(define-inlinable (ease-in-out t)
+ (if (< t 0.5)
+ (* 4.0 t t t)
+ (+ 1.0
+ (* (- t 1.0)
+ (* 2 (- t 2.0))
+ (* 2 (- t 2.0))))))
+
+(define-inlinable (ease-in-quart t)
+ (* t t t t))
+
+(define-inlinable (ease-out-quart t)
+ (let ((t* (- t 1.0)))
+ (- 1.0 (* t* t* t* t*))))
+
+(define-inlinable (ease-in-out-quart t)
+ (if (< t 0.5)
+ (* 8.0 t t t t)
+ (let ((t* (- t 1.0)))
+ (- 1.0 (* 8.0 t* t* t* t*)))))
+
+(define-inlinable (ease-in-quint t)
+ (* t t t t t))
+
+(define-inlinable (ease-out-quint t)
+ (let ((t* (- t 1.0)))
+ (+ 1.0 (* t* t* t* t* t*))))
+
+(define-inlinable (ease-in-out-quint t)
+ (if (< t 0.5)
+ (* 16.0 t t t t t)
+ (let ((t* (- t 1.0)))
+ (+ 1.0 (* 16.0 t* t* t* t* t*)))))
+
+(define-inlinable (ease-in-sine t)
+ (+ (* (- t) (cos (* t pi/2))) t))
+
+(define-inlinable (ease-out-sine t)
+ (* t (sin (* t pi/2))))
+
+(define-inlinable (ease-in-out-sine t)
+ (* (/ t -2)
+ (1- (cos (* t pi)))))
diff --git a/chickadee/scripting.scm b/chickadee/scripting.scm
index 7a661bb..5d24ce9 100644
--- a/chickadee/scripting.scm
+++ b/chickadee/scripting.scm
@@ -16,6 +16,8 @@
;;; <http://www.gnu.org/licenses/>.
(define-module (chickadee scripting)
+ #:use-module (chickadee math)
+ #:use-module (chickadee math easings)
#:use-module (chickadee scripting agenda)
#:use-module (chickadee scripting channel)
#:use-module (chickadee scripting coroutine)
@@ -42,12 +44,23 @@
"Wait DURATION before resuming the current coroutine."
(yield (lambda (cont) (schedule-after duration cont))))
-(define (tween duration start end ease proc)
+(define* (tween duration start end proc #:key
+ (step 1)
+ (ease smoothstep)
+ (interpolate lerp))
+ "Transition a value from START to END over DURATION, sending each
+succesive value to PROC. STEP controls the amount of time between
+each update of the animation.
+
+The EASE procedure controls the rate at which the animation advances.
+The smoothstep easing function is used by default.
+
+The INTERPOLATE procedure computes the values in between START and
+END. By default, linear interpolation is used."
(let loop ((t 0))
- (if (= t duration)
+ (if (>= t duration)
(proc end)
- (let ((alpha (/ t duration)))
- (proc (+ (* start (- 1 alpha))
- (* end alpha)))
- (wait 1)
- (loop (1+ t))))))
+ (let ((alpha (ease (/ t duration))))
+ (proc (interpolate start end alpha))
+ (wait step)
+ (loop (+ t step))))))
diff --git a/doc/api.texi b/doc/api.texi
index 1a56039..c3543b8 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -410,6 +410,7 @@ detection.
* Vectors:: Euclidean vectors.
* Matrices:: Transformation matrices.
* Rectangles:: Axis-aligned bounding boxes.
+* Easings:: Easing functions for interesting animations.
@end menu
@node Basics
@@ -435,6 +436,60 @@ Half of @var{pi}.
@node Rectangles
@subsection Rectangles
+@node Easings
+@subsection Easings
+
+@deffn {Scheme Procedure} linear @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} smoothstep @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-quad @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-out-quad @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-out-quad @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-cubic @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-out-cubic @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-out-cubic @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-quart @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-out-quart @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-out-quart @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-quint @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-out-quint @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-out-quint @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-sine @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-out-sine @var{t}
+@end deffn
+
+@deffn {Scheme Procedure} ease-in-out-sine @var{t}
+@end deffn
+
@node Graphics
@section Graphics
@@ -868,6 +923,7 @@ of scheduling tasks.
@menu
* Agendas:: Scheduling tasks.
* Coroutines:: Cooperative multitasking.
+* Tweening:: Animations.
* Channels:: Publish data to listeners.
@end menu
@@ -1069,6 +1125,37 @@ Wait for a message from @var{channel}.
Evaluate @var{body} in an endless loop.
@end deffn
+@node Tweening
+@subsection Tweening
+
+Tweening is the process of transitioning something from an initial
+state to a final state over a pre-determined period of time. In other
+words, tweening is a way to create animation. The @code{tween}
+procedure can be used within any coroutine like so:
+
+@example
+(define x 0)
+(coroutine
+ ;; 0 to 100 in 60 ticks of the agenda.
+ (tween 60 0 100 (lambda (y) (set! x y))))
+@end example
+
+@deffn {Scheme Procedure} tween @var{duration} @var{start} @var{end} @var{proc} [#:step 1 #:ease @code{smoothstep} #:interpolate @code{lerp}]
+Transition a value from @var{start} to @var{end} over @var{duration},
+sending each succesive value to @var{proc}. @var{step} controls the
+amount of time between each update of the animation.
+
+To control how the animation goes from the initial to final state, an
+``easing'' procedure may be specified. By default, the
+@code{smoothstep} easing is used, which is a more pleasing default
+than a simplistic linear function. @xref{Easings} for a complete
+list of available easing procedures.
+
+The @var{interpolate} procedure computes the values in between
+@var{start} and @var{end}. By default, linear interpolation (``lerp''
+for short) is used.
+@end deffn
+
@node Channels
@subsection Channels