Shaders Recently Started Compiling Every Time The Material Is Opened (4.27)

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Just in the last couple weeks, every time I open any material, in my project, its shaders have to recompile. If I close the material and immediately reopen it, they compile all over again.

Obviously, this is a total workflow killer… where can I dig to figure out what’s causing this?

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sorry to revive an old thread @SVR33 - did you ever find a fix or root cause for this?

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It’s been many, many moons since this… I hardly remember it but I did ultimately fix it.

Fix all redirectors on the entire project and check engine installation integrity. Quick and easy but probably won’t catch this issue.

I really like using Check All Blueprints Compile | Fab to run a compile check on the whole project… sometimes this plugin will turn up something that’s silently causing headaches like a texture in a material instance that’s a different format than it should be which happens to share some weird hard reference to something you forgot about.

Probably, now, I’d just delete the Intermediate, Saved and DDC folders from the project [backup first!] and then relaunch. That’s kind of the nuclear method but also maybe the best bet.

Hope that helps

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Thanks for searching through your memories! :smiley:
I did a nuclear purge at some point but things persisted - this particular issue was causing me grief as it seemed to perpetually invalidate a batch of HLODs when one of the materials in use was opened.

I did a bit more tracing and ended up in FMaterialEditor::UpdateThumbnailInfoPreviewMesh - this function is called when the material editor is opened and it causes a change to be logged every time

OriginalThumbnailInfo->PreviewMesh = MatInterface->PreviewMesh;
MatInterface->PostEditChange();

That PostEditChange() cycles an internal tracking value that caused my HLODs to invalidate. I thought this might be an old bug (as we’re in 4.27 still) but UE55 still has the same code. I may be completely off the mark when it comes to why/what it’s doing, but a simple change to

if ( OriginalThumbnailInfo->PreviewMesh != MatInterface->PreviewMesh )
{
	OriginalThumbnailInfo->PreviewMesh = MatInterface->PreviewMesh;
	MatInterface->PostEditChange();
}

.. so that the PostEditChange() only happens when there was a change fixed my HLOD woes for now.

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