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Implement Matrix4Tween.lerp() (#10829)

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Alan 2017-06-21 09:40:32 -07:00 committed by Ian Hickson
parent 3f3a36787e
commit 95f5d8d7f2
2 changed files with 38 additions and 6 deletions
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21
packages/flutter/lib/src/widgets/implicit_animations.dart
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@ -111,12 +111,21 @@ class Matrix4Tween extends Tween<Matrix4> {
Matrix4 lerp(double t) {
assert(begin != null);
assert(end != null);
// TODO(abarth): We should use [Matrix4.decompose] and animate the
// decomposed parameters instead of just animating the translation.
final Vector3 beginT = begin.getTranslation();
final Vector3 endT = end.getTranslation();
final Vector3 lerpT = beginT*(1.0-t) + endT*t;
return new Matrix4.identity()..translate(lerpT);
final Vector3 beginTranslation = new Vector3.zero();
final Vector3 endTranslation = new Vector3.zero();
final Quaternion beginRotation = new Quaternion.identity();
final Quaternion endRotation = new Quaternion.identity();
final Vector3 beginScale = new Vector3.zero();
final Vector3 endScale = new Vector3.zero();
begin.decompose(beginTranslation, beginRotation, beginScale);
end.decompose(endTranslation, endRotation, endScale);
final Vector3 lerpTranslation =
beginTranslation * (1.0 - t) + endTranslation * t;
// TODO(alangardner): Implement slerp for constant rotation
final Quaternion lerpRotation =
(beginRotation.scaled(1.0 - t) + endRotation.scaled(t)).normalized();
final Vector3 lerpScale = beginScale * (1.0 - t) + endScale * t;
return new Matrix4.compose(lerpTranslation, lerpRotation, lerpScale);
}
}

23
packages/flutter/test/animation/tween_test.dart
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@ -5,6 +5,7 @@
import 'package:flutter_test/flutter_test.dart';
import 'package:flutter/animation.dart';
import 'package:flutter/widgets.dart';
import 'package:vector_math/vector_math_64.dart';
void main() {
test('Can chain tweens', () {
@ -49,4 +50,26 @@ void main() {
expect(tween.lerp(0.5), equals(Rect.lerp(a, b, 0.5)));
expect(tween, hasOneLineDescription);
});
test('Matrix4Tween', () {
final Matrix4 a = new Matrix4.identity();
final Matrix4 b = a.clone()..translate(6.0, -8.0, 0.0)..scale(0.5, 1.0, 5.0);
final Matrix4Tween tween = new Matrix4Tween(begin: a, end: b);
expect(tween.lerp(0.0), equals(a));
expect(tween.lerp(1.0), equals(b));
expect(
tween.lerp(0.5),
equals(a.clone()..translate(3.0, -4.0, 0.0)..scale(0.75, 1.0, 3.0))
);
final Matrix4 c = a.clone()..rotateZ(1.0);
final Matrix4Tween rotationTween = new Matrix4Tween(begin: a, end: c);
expect(rotationTween.lerp(0.0), equals(a));
expect(rotationTween.lerp(1.0), equals(c));
expect(
rotationTween.lerp(0.5).absoluteError(
a.clone()..rotateZ(0.5)
),
moreOrLessEquals(0.0)
);
});
}