Description

UE4 applies 1-x transform to V coordinate when importing UVs from mesh. This is to handle GL/D3D differences in texture origin, but it breaks UDIM page addressing. It's possible to apply a fix to imported UVs, but this will break UVs intended for wrapped sampling, rather than UDIM sampling. Alternately, UE4 could adjust UDIM layout to match the modified UVs.

Steps to Reproduce

Import texture/mesh from the attached udimTest.zip. UDIM tiles should show up on the grid mesh with 1001 in the lower left corner, with X-axis increasing to the right, and Y-axis increasing upwards.

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Fixed
ComponentUE - Graphics Features
Affects Versions4.25
Target Fix4.26
Fix Commit12381769
Main Commit13654804
CreatedFeb 19, 2020
ResolvedMar 23, 2020
UpdatedSep 19, 2021
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