Cache interpolation attribute

[pechart]

Hi!
I just found the "cache interpolation" attribute for nParticles... Does that mean, that you guys found a way to make nParticle caches interpolate when retimed (slowed down)? That would be super awesome! I asked autodesk for this like... 100 times.

If so, what does interpolate? Position, Rotation, ...?

[ivaylo.ivanov]

"Cache interpolation" was added to work-around the bug in Maya that nParticles don't interpolate between frames. This makes them unusable with motion blur for example, if you don't cache them properly (or don't know how). When you enable this option, V-Ray will try to do what Maya must do - read the two cache frames and calculate interpolated particle positions. However, we do this quite inefficiently, since we don't have direct access to the particle data, and must use hacks like changing the current time for example. This will break all dynamics that were not cached! In most cases MB will break them anyway though. But you will also have a performance penalty related to the export phase. I think we do this trick only for positions currently, but other attributes also make sense. My opinion is that you should not use this option, and talk with Autodesk to fix all particle issues they have. This option is there if you are desperate to get something working and can accept possible issues. I don't think we will go as far as retiming. We just want to give some sort of "fix" for issues that people generally assume as render related (even if they are not).

[pechart]

and talk with Autodesk to fix all particle issues they have

I contacted them several times exactly about this issue since nParticles got implemented. It looks like they don't want to fix it.
But good to know, that there's an option now! Thanks a lot!
I think the most important attrs would be positionPP, colorPP, radiusPP, opacityPP and rotationPP if someone wants to pipe particle data to an instancer.

Thanks again!