I'm trying to render a region of image to save some render time but textures seem to get blurry doing so. Increasing region size makes textures more blurry but it doesn't seem to affect geometry. I have tried disabling mipmapping but it didn't fix it. Tested on Houdini 20.0.653. Everything works correctly in CPU mode.

I wonder if you have the "Optix Denoiser" on? Try turning that off, if it is.... It's... places...

https://www.sidefx.com/docs/houdini/render/optixdenoiser.html [www.sidefx.com]

Optix is disabled, doesn't seem to be related with that. I included hip file if anyone is interested to confirm its not working.
I have also tried
- houdini versions 20.0.506 and 19.5.773
- principled shaders
- disabling dof
- adjusting shading quality/render settings

I can reproduce it on 20.0.685.

fixed in 20.0.697
thanks for reporting