Help with pause at the end of looping cyclic animation

kruze · November 30, 2023, 8:36am

Hey all!

I have looping and cyclic animation called ‘run’ on a 3D model. Please take a look and observe that at the end of every cycle there is a tiny pause. This is from JME3 game:

Since it’s a cyclic animation, its first and last frame is the same and that causes the pause:

[Album] run action in action editor

In Blender, it doesn’t cause an issue because by default the Playback Frame Range is set to 1 to 16, so the 0 frame is skipped and when it reaches the 16 frame it interpolates back to the 1 frame so there is no ‘pause’ at the end of the animation because of duplicate frames.

As far as I know there is no way to restrict animation playback in JME like this so I came up with the solution: I removed the last 16th keyframe (which is a duplicate of the 0th keyframe ) so from the 15th keyframe should interpolate to 0th frame and make the pause disappear:

[Album] removed last frame

However my problem is that the pause is still there. I also made a version where I removed the 0th keyframe and the pause is still there in JME but works perfect in Blender. It looks like that JME skips interpolation between the last and first frame. Did I configure something wrong? Am I using animcomposer the right way? I don’t understand what is going on.

Edit: It is also pauses at the end of loops in the JME SDK, when I freshly export to glb from Blender then right click > ‘convert to j3o binary’. Opening the j3o file has the same pauses.

Here is my code:

        Node modelNode = (Node) assetManager.loadModel("Models/some_model.j3o");
        Node armature = (Node) modelNode.getChild(0);
        rootNode.attachChild(modelNode);
        AnimComposer composer = armature.getControl(AnimComposer.class);
        composer.setCurrentAction("run");
        // OR..
        // composer.setCurrentAction("run_last_frame_removed");
        // OR..
        // composer.setCurrentAction("run_first_frame_removed");

Edit: fixed animation gif url

kruze · November 30, 2023, 6:26pm

Update: It looks like Blender GLB export does something unwanted. I have a 15 frame version of the run animation called ‘run_edited’ where I removed the 16th frame. So there are total 16 frames from 0 to 15 and it should loop perfectly in JME. However, after I exported the file as GLB, I imported it to a new empty blender project and this 16 frame long animation is exported as 17 frame long, the last two frames as duplicates of each other. I’m playing around with export settings now.

[Album] extra frame??

Edit: The 16th frame on the action editor is duplicate of 15th which is plain wrong.

pspeed · November 30, 2023, 6:37pm

I hope you figure this one out. It has long plagued all of my animations in Mythruna and I’ve just resolved to “deal with it later”.

…but for my run and walk animations, I’ve carefully tuned the animations so that the feed don’t slide on the floor when at the proper speed of motion and it always bugs me to see that one frame slip every time.

kruze · November 30, 2023, 7:05pm

So I managed to make things better, but I still have this slight pause but not as severe as before.

In my exported animation there was an extra duplicate frame at the end. The reason for this was that Manual Frame Range was enabled on the ‘run_edited’ Action (also on some other actions) and the End frame was set not to the last 15th frame that contained the last keyframe but to 16. This caused the Blender GLB exporter to sample one more frame and it took the last frame at put it in there a second time.

[Album] Turn Manual Frame Range off

After turning this off the pause became much less noticeable but it is still there. It is more noticeable in the JMonkeyEngine SDK if I convert to j3o and preview it. It is less noticeable in the game loading up the same j3o file but it is still there and makes me go crazy.
Putting Blender, my previous gif and the game windows side by side it is clearly visible that I made things better but there is still a little tiny bit pause there. I’m on 3.4.0-stable by the way.

Ali_RS · December 1, 2023, 3:06am

You may fine tune it further with ClipAction.setTransitionLength(). It sets the animation transition duration. (e.g. when animation switched or restarted). In another word, if you set it to 0, it will instantly jump back to the beginning, when animation ended. Default value is 0.4 seconds.

github.com

jMonkeyEngine/jmonkeyengine/blob/3618ff0f1849d56d57f1f2869e16789de38b5ad6/jme3-core/src/main/java/com/jme3/anim/tween/action/BlendableAction.java#L107


      
          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) {
              if (transitionLength < 0.0) {
                  throw new IllegalArgumentException("transitionLength must be greater than or equal to 0");
              }
              this.transitionLength = transitionLength;
              this.transition.setLength(transitionLength);
          }
          
          protected float getTransitionWeight() {
              return transitionWeight;
          }

Edit:

Also be aware of this caveat:

github.com

jMonkeyEngine/jmonkeyengine/blob/3618ff0f1849d56d57f1f2869e16789de38b5ad6/jme3-plugins/src/gltf/java/com/jme3/scene/plugins/gltf/TrackData.java#L139-L142


      
          if (times[0] > 0) {
              //Anim doesn't start at 0, JME can't handle that and will interpolate transforms linearly from 0 to the first frame of the anim.
              //we need to add a frame at 0 that copies the first real frame

capdevon · December 1, 2023, 9:34am

I suggest you upgrade JME to the 3.6.1-stable version and retest. Each new version of JME always fixes a lot of bugs, it is not a good choice to stay with an old version.
And then follow @Ali_RS 's advice (I’m glad you’re back, it’s been a while since I’ve seen you)

kruze · December 1, 2023, 9:46am

Thanks for the advice! I’m gonna upgrade tonight and report back.

pspeed · December 14, 2023, 2:18pm

Maybe this is a Blender version issue but I’ve searched the obvious places in the UI and I cannot find this setting.

Any tips?

kruze · December 16, 2023, 8:56pm

Sorry, I just got to sit down do my own stuff again.

I’m using Blender 3.3.1.
Go to ‘Dope sheet’, then select ‘Action editor’.
Then either select an existing action or add a new one.
Then while the mouse is over the action editor’s ‘Timeline’, press the N key.