I don’t know if it’s because of search engine ensh*tification, but I couldnt find a solution to this problem. And whether there is something I need to do in-engine, or in blender to fix animation blending.
I could have sworn I’ve experienced this issue ages ago, but I just can’t find out how it was solved.
Basically anything inbetween the two animations, the scale of various mesh parts get really big. I tried messing additive options, but they don’t seem to fix anything.
And since I need to blend a lot of animations for the character, this is something I need to figure out the cause of sooner rather than later.
Is there something I’m not taking into account? There isn’t some scale issues from the source, they’re all 1:1 scaled, no changes.
yeah, that “ballooning” between two poses is almost always a scale track sneaking into the blend. one anim has a bone with scale ≠ 1 (often from IK/stretch in the DCC), the other doesn’t, and UE just interpolates that scale… so mid-blend the mesh puffs up.
quick sanity checks: make sure both clips use the exact same skeleton and retarget/base pose in persona. open each animation in UE, scrub a suspect bone (pelvis, spine, thighs, arms, any IK/stretch bones) and watch its scale values—if you see anything other than 1.0, that’s your smoking gun.
fast fixes that usually sort it: strip scale tracks from the animations in UE or re-export without scale keys from blender. if you need stretch in one clip, keep it consistent across all clips that will blend in that space, or lock it to 1. in the skeleton tree, set retargeting so scale comes from the skeleton instead of animation for most bones (leave exceptions only where you truly need animated scale). for additive clips, double-check the additive type and base pose—use the same reference pose the source was authored against; a mismatched base can look like bad scale during blends.
on the blender side, apply transforms on mesh and armature (so they’re truly 1,1,1), bake constraints before export, avoid non-uniform scaling on bones, and export with units handled properly so there’s no object-level scale coming through. IK rigs that auto-stretch are common culprits—bake to a deformation rig that doesn’t scale bones, or disable/stretch-to before baking.
if you share one short clip where the swelling happens and name a bone that looks worst mid-blend, i can tell you exactly which track to nuke or what retargeting setting to flip.
