Inconsistencies with Anim component.

Description

Recently I was working with animations and met with various problems. Two of them I was able to isolate and reproduce consistenly.

1. Adding layer via code seems to overwrite Base layer temporary if no animations are added to anim base layer.

https://playcanvas.com/project/1216249/overview/anim-layer-bug

var upperBodyLayer = this.entity.anim.addLayer(
        'UpperBody',
        this.blend,
        upperBodyMask,
        pc.ANIM_LAYER_ADDITIVE
    );

After adding new layer, logs shows that baseLayer name becomes added layer name. However if you assign any animation to base layer it becomes a mess.

-----------------------BEFORE ASSIGNING ANIMATION----------------------
this.entity.anim.baseLayer.name= : UpperBody
upperBodyLayer.name= : UpperBody
this.entity.anim.findAnimationLayer(`UpperBody`).name = : UpperBody
this.entity.anim.assignAnimation(“ClapAnim”, this.clapAnim.resource);

Animation layers are corrupted after assigning animation via code.

----------------------AFTER ASSIGNING ANIMATION----------------------
this.entity.anim.baseLayer.name= : Base
upperBodyLayer.name= : UpperBody
this.entity.anim.findAnimationLayer(`UpperBody`).name = : Base

That follows transitions not working and other weird behaviors.

2. Anim component additive layer mode does not work correctly if anim component is not on entity with Render component.
   https://playcanvas.com/project/1215543/overview/breaking-the-rig 1
   If Anim component is on different entity than Render component, then animations in same Base layer works correctly, but if you add another layer and set blend type to additive weird scaling behavior happens. It scales down model in weird proporsions.
   

3. There were more problems, but them was on editor and harder to reproduce. Like changing root bone, then trying to create new Mask, sometimes the root bone change is not updated until you create mask, delete mask and create again. Sometimes you need to hcange root bone several times. I was not able to find correct sequence to reproduce these, but layers with mask should be reviewed by someone a bit.

I created forum post about it as well:
https://forum.playcanvas.com/t/confusion-about-animation-blending/35772/9

Start by reproducing the layer and additive-blending cases in the linked PlayCanvas projects, then inspect the Anim component behavior for layers, masks, and entity/render relationships. Compare the reported layer names before and after assignAnimation and the model scaling when Render is on another entity. Done means the reproducible cases are isolated and corrected, with the mask-editor behavior separately confirmed or documented.