Packed geo Motion blur

[julientourignygagnon]

Hi.

I'm currently unable to obtain motion blur on render using Houdini and HtoA for a destruction sequence in a shot.

This is a standard rbd setup using a packed .bgeo.sc geometry file. I am transforming this geo using the bullet simulation points transform attributes with the "Transform Pieces" SOP. It allows me to have @v attribute on my packed geo but Arnold doesn't seem to pick it up even though motion blur is enabled on my ROP.

It seem to be due to the fact that my geo is packed since upacking it and transfering @v from the packed geo to the unpacked geo allows motion blur to work. This is a very noticeable performance hinder at render time since the geo is heavy and unpacking adds useless overhead.

I was wondering, what is the proper "clean" workflow to render rbd simulation sequences from Houdini with Arnold? Would creating a .ass archive solves the problem? If so, do i have to export each frame, unpacked, to the archive? If so, it seems like a waste of hard drive space and time...

Hoping someone can shed some light on this.

[schwungsau]

transform pieces is mantra specific node. with an external renderer, you need a different workflow.
you need to write out an alembic or sass file for each piece and use the instancer node. on instancer particles you create a string attr. which points to ass file/pieces. that's most efficient way. the same workflow, if wanna use redshift/Renderman etc...

[julientourignygagnon]

Ok, i will try this. Do you know how would material assignement works if i have various material assignements based on groups and @path and sometimes on the same piece? (for example a material for the inside of a broken piece of wood and another for the outside) If i apply the material on the instance points using those attributes will it work?

[schwungsau]

if you write export an ass file with shaders, it will work