[SOLVED] Animation does not loop properly

gump74 · May 13, 2020, 7:05am

Greetings all,
I tried to find a similar thread to my problem but could not find anything close to what I am experiencing. That, or I do not know what to google. I made a model in blender with animations. The model’s name is Lisa, lisa is now famous because she is on the internet. The animation plays well in loop in blender. I will attach an animated gif here:

LisaInBlender

I brought lisa into JME and converted .blend into .j3o. In the scene view the animation plays well. I will attach an animated gif here:

LisaInSceneView

When I play the game the animation starts correctly, but then stutters inbetween loops. It is a walk animation. the start frame is identical to the end frame. I will attach an animated gif here:

LisaInGame2

As you can see the animation stutters, if that’s the best word. in the simple update loop I have:
(edit) ok that does not really show the studder well. I will attach another animated gif here.

LisaInGame3

This one seems to show that at the end of the walk cycle lisa returns to idle…

animationChannel.setAnim("walking-baked", 0.2f); 
animationChannel.setLoopMode( LoopMode.Loop );

I copied the code in the program from " Walking Character" tutorial. I can attach the whole java file if someone would like it. I can also attach the j3o and the blend file if those would be helpful. I have tried setAnim with no blend time, same reaction. I have tried 0 blend time, plays animation once then stops in t-pose. Well ok, its more of a sloppy t-pose. I have tried .1f to 10f in increments, but not every increment. I do not under stand why this jitter would be happening. Any insights would be fantastic. Thank you in advance.

gump74 · May 13, 2020, 7:27am

Well, after I edited the thread to show the stutter better I noticed that it was playing the idle animation at the end of the walk cycle. I checked onAnimCycleDone and it had “channel.setAnim(“idle-baked”);” I commented that out and now it works great.

remy_vd · May 13, 2020, 7:46am

Also make sure that your animation has enough keyframes (>50). When it’s lower than this, JME has some issues calculating the correct interpolation that can cause weird looping behaviour.

gump74 · May 13, 2020, 8:44am

oh thank you for that tip, I was not aware of that.

mitm · May 13, 2020, 2:13pm

24 key frames per sec of animation. The same as film. Seems to work pretty good.

Edit: What is it about 50 that makes the difference? Just curious since this is the first I heard of this.

remy_vd · May 13, 2020, 2:22pm

The 50 is not a magic number, it’s just a number I picked. Probably > ~30 will also be ok.
I know there is something about jme not properly interpolating between the first and last key frame of an animation. Or at least it used to be.

If your animation has a very low number of keyframes you can get pauses between the loop.

pspeed · May 13, 2020, 2:23pm

This is with gltf and setting the interpolate key frames option? Or some other unrecommended way?

Ali_RS · May 13, 2020, 2:32pm

Note, this pause can happen if the first and last frames are the same (common on looping animations i.e walk, run,…) it’s because of default transitionLength

github.com

jMonkeyEngine/jmonkeyengine/blob/f808187142b79fa6c82c38b58ba09b71c90aa2bb/jme3-core/src/main/java/com/jme3/anim/tween/action/BlendableAction.java#L14


      
          import com.jme3.anim.tween.Tween;
          import com.jme3.anim.util.HasLocalTransform;
          import com.jme3.math.Transform;
          import com.jme3.util.clone.Cloner;
          import java.util.Collection;
          
          public abstract class BlendableAction extends Action {
          
              protected BlendableAction collectTransformDelegate;
              private float transitionWeight = 1.0f;
              private double transitionLength = 0.4f;
              private float weight = 1f;
              private TransitionTween transition = new TransitionTween(transitionLength);
          
              public BlendableAction(Tween... tweens) {
                  super(tweens);
              }
          
              public void setCollectTransformDelegate(BlendableAction delegate) {
                  this.collectTransformDelegate = delegate;
              }

In JME 3.3 you can fix it by setting it to 0 for looping animations.

github.com

jMonkeyEngine/jmonkeyengine/blob/f808187142b79fa6c82c38b58ba09b71c90aa2bb/jme3-core/src/main/java/com/jme3/anim/tween/action/BlendableAction.java#L75


      
          protected abstract void doInterpolate(double t);
          
          public abstract Collection<HasLocalTransform> getTargets();
          
          public abstract void collectTransform(HasLocalTransform target, Transform t, float weight, BlendableAction source);
          
          public double getTransitionLength() {
              return transitionLength;
          }
          
          public void setTransitionLength(double transitionLength) {
              this.transitionLength = transitionLength;
              this.transition.setLength(transitionLength);
          }
          
          protected float getTransitionWeight() {
              return transitionWeight;
          }
          
          /**
           * Create a shallow clone for the JME cloner.

mitm · May 13, 2020, 2:38pm

Thanks for the clarification, I will add this to wiki.