Arnold for Houdini: Beginner problems - doesn't render textures

[marque_pierre]

Hello folks,

After enjoying myself immensely shading in Mantra (Kursk and Angel Has Fallen) for two years, I now find myself in a new Houdini situation: Arnold. Why Arnold? It is one of those situations where multiple vendors are handling the same assets, so my hands are tied here.

Anyway, I have no end of trouble getting Arnold to render my textures. Primitives or existing geometry assets can be shaded and lit, but once textures are added to the mix... nothing (that is they render black as that is the missing textures colour). I must be missing something painfully obvious.

My best guess is that Arnold somehow doesn't automatically pick up the UVs of the primitives or other imported geometry, because if I add a UV texture node to my box primitive, I can get textures on it. But the primitives' native UV layout is lost (or never activated).

So... who can be the man of the hour and point me in the right direction?

[marque_pierre]

After much testing and reading of documentation, it simply boils down to UDIM tags. Houdini has its own lovely way to handle UDIMs in its image nodes. The Houdini Arnold implementation doesn't support this. So you need to manually type in Arnold's own UDIM tags <UDIM> into the file name in order for Arnold to read your multi patch textures. So...