ModelAnimator

This class provides support for animating an AnimatableModel

Usage

By default the ModelAnimator can play the full ModelAnimation starting from 0 to the animation duration with:

ofAnimation

If you want to specify a start and end, you should use:

ofAnimationTime

ofAnimationFrame

ofAnimationFraction

Use cases

Simple usage

On a very basic 3D model like a single infinite rotating sphere, you should not have to use ModelAnimator but probably instead just call:

animate

Single Model with Single Animation

If you want to animate a single model to a specific timeline position, use:

ofAnimationTime

ofAnimationFrame

ofAnimationFraction

• A single time, frame, fraction value will go from the actual position to the desired one
• Two values means form value1 to value2
• More than two values means form value1 to value2 then to value3

ModelAnimator.ofAnimationFraction(model, "VerticalTranslation", 0f, 0.8f, 0f).start();

Single Model with Multiple Animations

If the model is a character, for example, there may be one ModelAnimation for a walkcycle, a second for a jump, a third for sidestepping and so on.

ofAnimation

ofMultipleAnimations

Here you can see that no call to animator.cancel() is required because the animator.setAutoCancel(boolean) is set to true by default.

ObjectAnimator walkAnimator = ModelAnimator.ofAnimation(model, "walk");
walkButton.setOnClickListener(v -> walkAnimator.start());

ObjectAnimator runAnimator = ModelAnimator.ofAnimation(model, "run");
runButton.setOnClickListener(v -> runAnimator.start());

AnimatorSet animatorSet = new AnimatorSet();
animatorSet.playSequentially(ModelAnimator.ofMultipleAnimations(model, "walk", "run"));
animatorSet.start();

Multiple Models with Multiple Animations

For a synchronised animation set like animating a complete scene with multiple models time or sequentially, please consider using an android.animation.AnimatorSet with one ModelAnimator parametrized per step :

AnimatorSet completeFly = new AnimatorSet();

ObjectAnimator liftOff = ModelAnimator.ofAnimationFraction(airPlaneModel, "FlyAltitude",0, 40);
liftOff.setInterpolator(new AccelerateInterpolator());

AnimatorSet flying = new AnimatorSet();
ObjectAnimator flyAround = ModelAnimator.ofAnimation(airPlaneModel, "FlyAround");
flyAround.setRepeatCount(ValueAnimator.INFINITE);
flyAround.setDuration(10000);
ObjectAnimator airportBusHome = ModelAnimator.ofAnimationFraction(busModel, "Move", 0);
flying.playTogether(flyAround, airportBusHome);

ObjectAnimator land = ModelAnimator.ofAnimationFraction(airPlaneModel, "FlyAltitude", 0);
land.setInterpolator(new DecelerateInterpolator());

completeFly.playSequentially(liftOff, flying, land);

Morphing animation

Assuming a character object has a skeleton, one keyframe track could store the data for the position changes of the lower arm bone over time, a different track the data for the rotation changes of the same bone, a third the track position, rotation or scaling of another bone, and so on. It should be clear, that an ModelAnimation can act on lots of such tracks.

Assuming the model has morph targets (for example one morph target showing a friendly face and another showing an angry face), each track holds the information as to how the influence of a certain morph target changes during the performance of the clip.

In a glTF context, this Animator updates matrices according to glTF animation and skin definitions.

ModelAnimator can be used for two things

• Updating matrices in TransformManager components according to the model animation definitions.
• Updating bone matrices in RenderableManager components according to the model skin definitions.

Every PropertyValuesHolder that applies a modification on the time position of the animation must use the ModelAnimation.TIME_POSITION instead of its own Property in order to possibly cancel any ObjectAnimator operating time modifications on the same ModelAnimation.

More information about Animator: https://developer.android.com/guide/topics/graphics/prop-animation