Jez Smith

until it gets fixed properly i know of one hack to fix the clearing.
It is to create a single point that exists when there are no particles present in the particle system.
in your asset or cache, if you drop down a switch node and set the switching expression to “if(npoints(”../yournode“)==0, 0, 1) where ”your node" is the output of the particle sim. Set input 0 of the swtich node to a single point with an id of 999999999 or something high so there is no conflict, and make sure it has all the same point attributes etc as what will come out of your particle sim, set input 1 to your particle sim output.
Then maya should play nicely and your non moving, single point should ‘stand in’ for the particle sim when there are no points.

hope that helps

thanks for your reply.
it seems that is you try the expression on any of the ‘internally mapped’ attributes then you receive that error, but if you try it on other custom attributes it works fine.

By chance i was only trying it with attributes like opacity, pscale (all of the mapped ones). So i was getting the error every time.

So in summary, it works as it should, and they can be exported to arnold just as any maya particle attribute. But maybe you can make a note of this error?

Thanks

Hi,

I'm reading in a bgeo cache with a hda that just contains a file sop.
Engine correctly loads the particles and maps the per point attributes to dynamic per particle attributes in maya.

However, if i try and query these attributes using
particle -id X -attribute Cd -q particleShape
or
particle -order X -attribute Cd -q particleShape
i get the error:
// Error: line 1: Could not find specified particle. Please check the value passed to -id or -order. //
but the particle does exist

If i do the same thing with a maya created nparticle system i get the value of that attribute from the corresponding point.

Is there a difference in the attributes the houdini engine creates and the ones maya creates?

The reason i am asking is that i can't get arnold to pick up any of my custom attributes (floats and vectors) from houdini engine nparticles (apart from rgbPP)
It does work with maya nparticles.

Anyone have experience with this?