with current Houdini versions (starting with 15.5.553, I believe), I get the following error message when starting a render:
mantra: /shop/principledshader1/SurfaceVexCode:7171:20-30: Error 1066: Call to undefined function ‘getuvobject’. /shop/principledshader1/SurfaceVexCode:7172:25-40: Error 1066: Call to undefined function ‘getuvhiresobject’.
mantra: Failed to resolve VEX code opdefShop/principledshader?SurfaceVexCode
It doesn't matter whether I use the mantra surface shader or a simple principledshader.
This error also happens in 15.5.557. I think this is a high priority issue. Not being able to use materials is kind of a very… very.. big deal. How did this not get noticed?
Apparently, there was some issue with old shader code being cached in our regression tests, so the tests were using the old code and thus kept producing correct output, though that's half-heard 3rd-hand information, so I might have it wrong.