Artifacts will occur when using Camera Vector related features and Decal Actor Rotation is not the default value (0º,-90º,0º)
Camera Vector related features: POM | Fake Reflection | Fake Interior
MARS Decal Rotation Correct Widget can get Decal Axes from Decal Rotation, also get reverse Interior Rotation Axes and Set Vector Parameter for POM | Fake Reflection | Fake Interior Functions in Decal Material automatically
Also see complete product: MARS Master Material
Check details in: Document Link
Make sure to enable BlueprintMaterialTextureNodes Plugin
