This is a tricky issue with a multitude of things that could possibly be wrong, depending on what the error says in the “Output Log”. I have been troubleshooting the issue the past couple of days and I think I have a solution. One is real simple, and I will leave that for last.
First thing to do, save the file with the animations into another file, so you can alter the file and not lose your work(Basically, open the blend file with the transform problem and “save as” a new file).
Next, open the new file and delete all the animations. Click the skeleton and go to object<apply<all transformations.
Next, while skeleton is selected, go to pose mode and got to pose<apply pose as rest pose.
In the object editor tab(while in pose mode), go to the pose section and click on the rest position button; then the pose position button and make sure they match.
Next, got to the timeline in the default “layout” tab and change it to the dope sheet and got to the action editor section. Add a new action, name it whatever you want, and make an animation.
Now you need to save because everything should be right. This will be the new altered file to see if its you or the Unreal Engine FBX.
Now you need to select the model then shift+select the armature.
File>export>export FBX.
check selected objects.
highlight armature and mesh.
apply scaling change to FBX all.
x forward.
z up.
check apply unit.
check use space transform.
Leave everything else alone. In geometry; check tangent, and apply modifiers ( that should get rig of the no smoothing group error). In armature; uncheck leaf bones. What they are referring to by leaf bones is the ends of the last bones of the hierarchies( unless you are using their positions as sockets, or anything else).
Now open Unreal.
After all that, there might not be anything wrong at all. It might be the FBX importer. Import the file. If the error comes up, you know everything is right so what is the problem?
Check the out put log. it should say the bone. Hopefully it is one bone and it should be the root bone of the armature.
Check out the numbers on the source transform and the converted transform. They are listed in order as: transform position, transform rotation, and transform scale.
Look at the numbers. Coming from blender, if you have the import options in unreal set as force x forward, there should be a difference in the rotation. If you changed the import scale in unreal, there should be a difference in the scale sections. You want both the source and the converted transforms to match.
So what is the problem?
Simple fix, it’s the FBX importer.
Now delete the files that were just imported.
Import the same file, but this time you are going to fix the problem.
When the options for the importer pop up, with check marks on import mesh and skeletal mesh, look at the options. Look at two specific fields; import scale, and force x forward.
Now that you know what they say, uncheck import mesh at the top of the import options menu.
Scroll down to the two spots again; scale and force x forward. They should be different from when you had import mesh checked. That is your problem.
When ever you change either field, it doesn’t update the other in the FBX importer options.
To solve the problem, and not have the problem for the next time you import a model with animations, make a different file location in Unreal for models and a spot for animations. Import the models and animations separate. Use the importer options in Unreal to extract them separately.
Hope that helps,
Steven Perkins(Trekkee_solo/Dblzero)