I have a simple set up with pyro and particles in Houdini to use as a HDA in Maya.
All appears as expected at first in Maya the particles are translating to nParticles in Maya of which I then cache to nCache and cache the fluid smoke as VDBs.
I then use a Vray volume grid for the VDBs and assign the nParticle cache to another nParticle (creating the same attributes if needs be)

I need to use Vray for rendering and with nParticles you have to activate additional attributes to pass rgbPP, age,and customScalar etc if I want to utilize a ramp within Hypershade and then connect to a Vray Shader.
Vray though doesn't recognise ‘normalised’ age which is needed to use a ramp (0-1) so notrmally I would create a mel expression to divided age bye LifespanPP and out out to a custom attribute Vray recognises. But this time this didn't work.
I investigated further and it seems that the age attribute from Houdini on a per particle basis isn't passing on to Maya and in Maya I get the same number on all the particles.

Now I have a work around by creating a custom attribute in Houdini to match the name of the ones vray recognizes i.e @userScalar1PP and get the normalized age by dividing the age by the life in an AttributeVop and pipe out to that custom attribute, and it works but I'm lost as to why isn't the @age passing on to Maya on a per particle basis? because all others pass on like @life (comes in to Maya as finalLifespanPP)
Am I missing something is @age named differently in Maya as it sees ‘age’ just not on a per particle basis!?

If I remember correctly, age in Maya is computed from the birthTime attribute - so I guess the real question is why we're not passing setting the maya birthTime based on the houdini age. I will have a look at the code in question.

juliap
If I remember correctly, age in Maya is computed from the birthTime attribute - so I guess the real question is why we're not passing setting the maya birthTime based on the houdini age. I will have a look at the code in question.

Great thanks Juliap.

Should be fixed tomorrow in 16.5.502. If the asset already sets birthTime, we use it, if not, and the asset sets age, we compute birthTime from age. If the asset does not set either age or birthTime, birthTime is 0 and the age is the current time.