Interchange Framework unusable due to lack of pivot handling settings ☹️

[Rawalanche]

Hi,

I wanted migrate my workflow from the old FBX importer to new Interchange Framework, but I couldn’t, because of the pivot point handling dealbreaker.

Then I wanted to see if I could use GLTF instead, and I couldn’t, because GLTF also uses Interchange Framework. Let me illustrate:

Imagine you have a simple vehicle asset: A body, 4 wheels, turret, and a gun.

You want each individual asset to have it’s own point, as if you apply the transforms of the individual meshes, you can no longer animate the wheels for example, because their pivot point is at the world origin, not their center.

Since you want to have clean workflow, you don’t want to have dozens of individual assets like “Body.fbx, Wheel_FL.fbx, Wheel_FR.fbx… etc” spilled in your interchange files folder. You’d like to have just one self contained “Car.fbx” file. Currently (with the soon to be legacy FBX importer), you can just do that, and export your entire vehicle as single FBX file.

All you have to do on the unreal side is to uncheck the “Transform Vertex to Absolute” checkbox in the import settings, and the importer won’t bake the transforms, effectively deleting the original pivot points from the DCC.

You can then bring your vehicle into the engine as single .FBX file, and unpack it into multiple meshes you can easily assemble into a car blueprint you can animate, especially if you also exported socket helpers:

By default, if you keep the Transform Vertex to Absolute checked, the meshes would become unusable on the UE end, as the pivot would be reset to world origin, making the basic transform animations impossible:

The problem with Interchange Framework is that it has no such option. It has obscene amount of import settings, but it just can not help itself and has to straight up delete any pivot points that come from the DCC.

Both FBX as well as GLTF are more than well capable of preserving the location of multiple meshes (containers of the primitives) in relation to the world origin. When importing exported GLTF or FBX of the car back into the DCC, all pivot points remain perfectly preserved.

The picture below shows FBX reimported back into Blender. The GLTF provided the exact same result. You can see the pivot dots being at their original places:

The only way to actually get the data correctly into UE with the Interchange Framework would be to author the scenes on the DCC end like this, where all the meshes locations are zeroed out:

This is obviously not feasible for many reasons. No artist would want to work like that.

So the only solution that remains are some really wonky scripting workarounds, where some python script zeroes out the locations on export, and then reverts them back after export is done. This is obviously a huge downgrade in terms of workflow overhead and reliability.

I would really love to start using the Interchange Framework, but I just can’t if it doesn’t support even something as trivial as having a choice to not straight up delete transforms of the imported meshes.

[Rawalanche]

Okay, after some more digging I found it. There are multiple stock pipelines, such as Asset, Material, Texture and SceneAsset.

• SceneAsset pipeline exists out of the box, but is not registered as one of the default pipelines to select. You have to add it manually in project settings:
  
  
• Then it will become available for selection in the GLTF import dialog:
  
  
• The default pipeline assets are stored in the engine assets folder. You can open them and compare their configuration. The culprit setting is called “Bake Meshes” (poor name IMO, should be “Bake Transforms”):
  
  
• This setting is hidden for both initial import and reimport for both Asset and SceneAsset pipeline. This makes some sense in terms of reducing room for user error, but wrecks the discoverability and understanding of what’s happening.
• If you have some “scene” as in multiple meshes that should be arranged in relation to each other while having the pivot preserved, you’d want to use the SceneAsset pipeline.
• If you have just a set of individual assets stored in one file, you want to use just the Asset pipeline.

[Rawalanche]

Unfortunately, there seems to be a dealbreaking bug with sockets. When Bake Meshes is disabled, you get proper pivot points but all the sockets exported in GLFT are zeroed out to origin:

When Bake Meshes is enabled, the pivots are zeroed out to origin but the sockets are on the right places:

This is quite embarrassing as for proper assembly of hard surface hierarchies, you need both: You need correct pivot locations and you need correct socket locations. With Bake Meshes ON you get wrong pivot locations but correct socket locations, with Bake Meshes OFF, you get correct pivot locations but wrong socket locations

[Rawalanche]

And one more bug:
The Offset Rotation only works if the Bake Meshes is Enabled. This is again a big issue since Unreal’s Front Axis is X+. The old FBX importer has “Force Front X Axis” checkbox exactly for this reason. The Interchange importer does not. If I have for example the car above, and I am not able to transform it to be X+ forward, all the direction named functions in BP and C++ such as “GetForwardAxis” will become a mental mess. There’s no reason the Offset Rotation should be restricted to only work when Bake Meshes is on.

[Drakgoku]

We need this in gltf

Why do we use gltf? It gives us all the textures without having to manually add them like FBX. It’s faster, simpler and weighs less than twice as much.

The other alternative from blender is:
1 - Press “A” (Select all objects)
2 - Press “CTRL” + “A” (Menu apply)

• Select All Transforms (Resets the position to (0,0) and its measurement)

3 - Delete all the “empty” (selecting above without the “CTRL”+“A”), so that only the meshes appear
4 - When you don’t have the empty ones, (as they are all at position (0,0) but in reality they are far from (0,0)) you have to select everything “CTRL”+“A” and do: Object → Set origin → origin to geometry. This will actually give you where the objects are located. You will notice that they are far from (0,0)
5 - Place the pivot

Form A - On axis 0.0

    ┌──|──┐
    │  |  │
 ───┼──|──┼─── (0,0) middle of geometry
    │  |  │
    └──|──┘

And select Individually or in groups the pieces you want to group and modify the transform of the object to leave it at (0,0). For groups (for example of 3 figures) you have to use the ALT.
Remember that the ALT is based on the figure/s. If you have other figures that you do not need, you do not have to select them otherwise it will be based on the others and the pivot will be complicated.

Form B - If you don’t want it in position 0.0 and you want it with respect to some axis:

    |
    |
    ┌─────┐
    │     │
    │     │
 ───┼─────┘── (0,0) Lower right corner from geometry
    |
    |

You select the piece or pieces you need, then edit mode and select vertices and put it in the vertex you like the most. Then when you have the vertex selected Object → Set origin → Origin to 3D Cursor.

Then you can export it again to the format you want. (you can export the parts you need.)
(Trial and error I found it)

There may be a faster way. But the pivot gives a lot of problems in all the other ways and this way you can put the (0,0) automatically without having to do it manually.

Note: In Maya I don’t remember it, I haven’t used it in too long.
Note: It’s not as simple as saying “I want them all at position (0,0)” since a game engine will never be at position (0,0) if you can’t have an absolute.