Difference between Vray RT GPU and CPU when rendering bump maps

[yannick1976]

Hello all !

I have noticed differences between vray RT GPU and CPU when rendering bump maps : it seems bumps are somewhat stronger with CPU.
What is the reason for this ? I am using vray RT 2.0 SP3 and have set bitmap size to maximum.

I wish both would be the same, because GPU is a lot faster, but has some limitations, so quite often I have to switch to CPU, and I would like my render not to change when I do

Thanks in advance,

Yannick

[vlado]

The CPU engine uses filtering for the bitmaps. On the other hand, the GPU always uses unfiltered textures. This may lead to differences in the bump mapping.

Best regards,
Vlado

[yannick1976]

Thank you for that quick answer !! You're right, the filtering is the difference, it also appears when using the bitmaps as diffuse maps.

Is there a way to let CPU render use the same filtering as GPU ? That would be perfect for me.
I tried playing with the bitmap filter settings (filter type and blur settings) : "None" is really different. "Pyramidal" and "Summed area" are better but I couldn't get the same as GPU.

Really hope you also have the answer to this...?

[vlado]

You could try setting the blur amount to a really small value.

Best regards,
Vlado

[yannick1976]

Mm, that still doesn't match... but I guess this is the best I'll get for now.

Thanks a lot for your answers !