I recently moved my 4.25 project to 4.26, and my niagara systems are no longer working because of the Skeletal Mesh Location module. The mesh has CPU Access enabled, the result in preview is different from what it is shown in playtime.
What the logs say, this issue persists for all skeletal meshes and every new emitter I make and even for new skeletal meshes that I import, CPU is unable to access the skeletal mesh regardless of what I do
LogNiagara: Skeletal Mesh Data Interface is trying to use triangle sampling function 'RandomTriangle', but either no CPU access is set on the mesh or the data is invalid. Interface: NiagaraDataInterfaceSkeletalMesh /Game/Particles/BowSpawnNiagaraEmitter1_System.BowSpawnNiagaraEmitter1_System:BowSpawnNiagaraEmitter1.SpawnScript_90.NiagaraDataInterfaceSkeletalMesh_1
LogNiagara: Skeletal Mesh Data Interface is trying to use triangle sampling function 'GetSkinnedTriangleDataWSInterpolated', but either no CPU access is set on the mesh or the data is invalid. Interface: NiagaraDataInterfaceSkeletalMesh /Game/Particles/BowSpawnNiagaraEmitter1_System.BowSpawnNiagaraEmitter1_System:BowSpawnNiagaraEmitter1.SpawnScript_90.NiagaraDataInterfaceSkeletalMesh_1
LogNiagara: Skeletal Mesh Data Interface is trying to use triangle sampling function 'RandomTriangle', but either no CPU access is set on the mesh or the data is invalid. Interface: NiagaraDataInterfaceSkeletalMesh /Game/Particles/BowNiagaraEmitter_System.BowNiagaraEmitter_System:BowNiagaraEmitter.SpawnScript_0.NiagaraDataInterfaceSkeletaMesh_0
LogNiagara: Skeletal Mesh Data Interface is trying to use triangle sampling function 'GetSkinnedTriangleDataWSInterpolated', but either no CPU access is set on the mesh or the data is invalid. Interface: NiagaraDataInterfaceSkeletalMesh /Game/Particles/BowNiagaraEmitter_System.BowNiagaraEmitter_System:BowNiagaraEmitter.SpawnScript_0.NiagaraDataInterfaceSkeletalMesh_0
For MW and anyone that comes across this, I resolved a similar issue with marketplace content doing a Full Rebuild on each Niagara system (It’s an option under the Compile arrow in the system). This works for most of the systems. Two systems would not rebuild and caused UE4 to hang indefinitely.
To resolve this, I built the 4.26.1 build from GitHub source and used it. Everything worked in that build. Not sure why the launcher build behaves differently.
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Another two years later, I found this happening to some meshes in 5.4 (animals from the asset store). Sorry for the revivify but this is the only discussion I’ve found on the subject at all. Setting the LOD CPU Access property on the sk meshes didn’t resolve the error. Neither did recompiles etc. However, I noticed the one mesh I use my Niagara system as the Preview Mesh was working okay. So going back into the Niagara system, in the Initialize Mesh Reproduction Sprite, I set the Preview Mesh to one of the non-working meshes and a CPU Error warning appeared in the details editor with a Fix Now button. Clicking that to clear the error, and repeating the process for the other meshes, allowed them all to work. I don’t know what the Fix Now button is changing on the mesh other than the CPU Access bool that was already set, but give it a try if your stuck.
