Hi guys,
When trying to import fbx with skeletal mesh exported from blender 2.7 and run through with fbx converter I’m getting warning that bone size is too small to create physics asset. Mesh is correct in size that is after importing it into UE4 and placing it next to 2m x 2m cube that mesh looks as is of good size.Any ideas why is that happening? I’m using UE4 4.6.1
Thank you.
How does the skeleton look in skeletal mesh editor? I’ve heard of this issue before; one way to fix it is to reset the bodies in Phat and set minimum bone scale to a smaller value while creating new bodies.
Hi Jacky,
Thank you for your reply.
The skeleton in mesh editor looks normal, that is, it looks exactly the same as it looks in Blender. I can see every bone, every bone has normal size.
Hi,
I’ve figured that out so I thought that I’ll post my steps here so perhaps somebody with similar problems can simply follow them and save 3 days of banging wall and floor with his head, here it goes:
1.Rig mesh and make animations in Blender
2. Remove every material from this mesh. After unlinking your materials, save your file. Then reload it with Ctrl+Shift+O. This will ensure that no extra slots are exported with this mesh and you have just one material slot in UE4.
3.Unlink any textures in image editor of blender
4. Export in ASCII fbx with Skeleton and Mesh selected:
Set:
scale:100 must be rescaled by 100 in blender and exported with scale 1, that is make mesh as you would with “regular” dimensions, scale it up by 100, reset scale to 1, and export with scale set to 1
Axis:X Forward, Y UP, if that doesn’t make the rotation OK, set in UE4 in skeletal mesh editor roll to -90
5. Run through Fbx Converter
6. Import into UE4 selecting
a) import normals and tangents
b)create physics asset
Best regards
Had the issue too and got it working with these settings.
I also had the “Bone size too small cannot create physics asset” error. Turns out… it’s probably a bug in Blender. There is a ticket for it and there is a workaround described:
You can also use metric units with 0.01 scene scale (and apply transforms so both the mesh and rig are 1.000 scale), that way you can still modify the mesh and get good results.
after u did the whole metric 0.01 scale bla bla bla thingy u need to press ctrl A and apply rotation and scale to fix the bone size too small for physics asset
I might have found another solution. I had to set to radius of the Heads and Tails of my bones in Blender to a rather higher value. I still got the warning saying the bones were too small to autogenerate a Physics asset. But when i manually created bodies for the Physics asset, the simulation worked fine. It doesn’t spas out anymore.
I had same problem at 4.23 version UE: export FBX from 3ds max and got “bone too small” error. Export from Maya – same. Then tried to create physic asset on base mannequin (epic’s one) – error. Tried create physic asset on 4.22 – error. Then I download 4.2 version – and engine created physics asset from mine FBX successfully. Same fine asset on 4.12.
So yes, another solution: create physics asset on 4.12 and migrate it to 4.23 UE.
Thank you
The best anwer!..you saved my life! +1000
I’ve been back and forth through every thread website linked here and spent the last 3 days attempting to fix the issue, I have finally come up with a fix adding together a few peoples answers to get one and I wanted to post to anyone who may run into the issue.
So, the first thing I did was select all within blender then > object > parent > clear all keep transform. I then select all again and, in the options, I set scale to 100, then Object > Apply > Scale.
I then select all and scale it all again from the options menu up 100 again.
Repeat the Object > Apply > Scale one last time then select all of your components Shift click the main body of your component. Then Object > Parent > With Empty Groups.
From Here I Export at A Scale Of 0.0001 . Import TO Unreal, I had a physics asset. from here I like to keep the assets clean and to correct scale, so I export from unreal to FBX again. open it in blender and export scaled down 0.1 another time. open in blender and save it so I can delete all of the over scaled assets. re import the normal sized asset back into unreal AFTER I deleted saved, then deleted the asset I already import to unreal (in case it crashes) anyway the physics asset works perfect, and the item is normal scale plus I have an fbx as normal scale. probably an easier way to do it but I struggled to find those other ways.
The same problem occurred in version 4.19. The solution turned out to be scaling the skeleton and mesh in Blender to a physically correct size. That is, my skeleton was 18 centimeters and I increased it 10 times to 180 cm. I applied transformations to the skeleton and mesh. But so that the mesh in the Engine was the right size, I made the Unit Scale 0.1. This helped.
This happened to me just this morning. The fix turned out to be to unparent my mesh from my armature in Blender, Ctrl+A on the mesh to zero it’s transforms out, and THEN reparent the armature to the mesh.
TLDR; Apply your scales to everything before you parent your armature.
None of these fixes work, including the most recent ones. What is the actual issue here? Minimum bone size is set to 20 by default, so this is not the issue - most skeletons are more than 20 cm in length. Unless you are rigging ants, this is not the problem. I am importing bones that are 50cm in length and still generating the same error so the value for bone scale is not being interpreted correctly on import.
Presumably this is a bug with blender’s bone export transforms because entering a minimum bone size of 0.00001 cm is obviously not the correct way to do this.
