hi All,
From Version 31.20 (16th September 2024) you CAN only have a thumbnail at Power of 2 (1024 x 1024). In the newer versions of UEFN, this will be enforced by the publishing update servers even further
the value described in the text 1920x1080 wont be accepted there is a function called “Conform Texture” which ENFORCES the Power of 2, but thumbnails are silently refused
the nearest 2 power is 1089.
The past discussion is 2048 x 2048, 2048 x 1024 and cropping in applications like Windows PAINT
specification
Thumbnails can be at least 1920x1080 (16:9 aspect ratio) for rectangular images and 1024x1024 for square images, up to 5MB in size.
maybe 2048 x 1024 and 2048 x 2048 is inside the 5mb
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post about this
Uploading thumbnail - General / Issues and Bug Reporting - Epic Developer Community Forums (unrealengine.com)