Our art team imported a series of meshes, but only this particular mesh encountered unexpected issues.
- This mesh fails to generate valid Nanite data, and the SDF data is also invalid.
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- Importing the same FBX file as a brand-new asset yields normal results.
- However, reopening this mesh and re-importing it in the editor from the FBX file still produces problems.
- No adjustments to the mesh’s Nanite construction settings can resolve this issue.
Even if re-importing solves the problem, we seek deeper insight into this bug to implement a permanent workaround. Locating this anomalous mesh required significant effort.
We request Epic’s support team to provide additional information, such as: What specific cause prevents this mesh’s Nanite data from constructing correctly?
Really thanks!
Hello,
Thank you for reaching out.
I’ve been assigned this issue, and we will be looking into it for you.
Hello,
It looks like this Static Mesh has a member “bDoFastBuild” set to true, that is intended to mark runtime-created Static Meshes for fast build.
This member can be enabled by calling “UStaticMesh::BuildFromMeshDescriptions(…)” or “UStaticMesh::BuildFromStaticMeshDescriptions(…)” (a blueprint-callable function), if they have “Params.bFastBuild” or “bFastBuild” respectively enabled in the params.
Once set, there is no method to unset this member without custom C++ code.
Have you run this mesh through either of these functions?
Please let us know if this helps.
Hello Stephen!
Really thanks for your info. ‘bDoFastBuild’ is really helpful to us
> This member can be enabled by calling “UStaticMesh::BuildFromMeshDescriptions(…)” or “UStaticMesh::BuildFromStaticMeshDescriptions(…)” (a blueprint-callable function), if they have “Params.bFastBuild” or “bFastBuild” respectively enabled in the params.
> Once set, there is no method to unset this member without custom C++ code.
> Have you run this mesh through either of these functions?
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I checked the in-house tool we used, I don’t think we modified the ‘bDoFastBuild’.
But I want to know if this is a possible case:
- Our tool imported a mesh in async mode, but it doesn’t wait until the import process finished. Before it finished, the user saved that mesh.
Still, really thanks for sharing the ‘bDoFastBuild’ info. It helps us a lot.
Luo
Hello,
Without having a better understanding of how your import tool works, we cannot say for certain if saving mid-import could cause bDoFastBuld to be enabled.
Are you using the Interchange plugin? There is a theoretical link between this plugin and bDoFastBuild, but it has not been confirmed.
We have created a bug report for this behavior with bDoFastBuild becoming enabled in-editor.
The tracker will be visible after it is approved internally at Epic Games and is publicly accessible.
Please let us know if this helps.
Hello Stephen!
Really thanks for your following. We need more time to investigate our own tools. But your answer is already very helpful.
Please let me select your answer as the best answer and close this.