[Sidefx-houdini-list] basic instancing question

jon parker parker.jon at gmail.com
Thu Oct 23 00:13:06 EDT 2008

Greetings esteemed Houdini masters!
I've been tasked to create a planetary nebula by some very demanding
scientists... I've done some lighting for studios using Houdini in the
past, but now the holes in my knowledge about Houdini are showing up,
so I am looking for some basic workflow questions to be cleared up.
For the nebula, the basic gas volume is looking great, however there
are a large number of 'knots' in the nebula that need to be quite
detailed.  I tried using volumetric metaballs first, but these don't
seem to shade as nicely as the volume primitives... the density
gradients don't seem as smooth, and the edge glows just aren't there
like they are with volumes.  Converting them to i3d files gave me a
much better look, but that's quite time consuming during look
development, since I need at least 1024^3 i3d files to maintain the
detail.  So I've tried instancing volumes to each knot, and this
potentially looks best, except I have two questions about it...
firstly, what is the best way to transfer point attributes to the
volume?  Secondly, how can I use world space displacement on an
instance?  On the first attempt I discovered that instances themselves
are not displaced; instead they pick up the displacement of the source
geo before they are instanced.   Aside from this question, which
approach makes the most sense?  There are obviously a lot of potential
paths to take in Houdini.

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