Jeff Wagner

old_school

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VFX Artist
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Canada
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obj-image ILLUME Webinar
FLIP Fluids | Part 1
obj-image ILLUME Webinar
FLIP Fluids | Part 2
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Pyro FX | Tips and Tricks
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Geometry Workflows in H16
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Learning Houdini

Recent Forum Posts

Particle Lifetime measured in seconds? not for me! June 12, 2019, 5:46 p.m.

Your approach is a good one. Using a volume to create a lattice of points is one way.
Another is to create a density field and scatter points by volume as well.
This second approach allows you to scuplt the density with noise to create a non-uniform distribution.

If you “want” a uniform distribution of points, you can also use a Box SOP set to lattice and add the internal divisions then use an Add SOP to delete the geometry but keep the points.

I believe the offset may be due to the original bean's origin not aligning with 0,0,0 in the current object. Or if you are using a bean at the object level, there may be a transform present there that is causing the offset.

I whipped up a quick file to show one way to create floating coffee beans around a mug using Bullet Simulation to add motion and to solve for self-intersections.


Note:
- how to construct a proper convex decomposition for the mug to help Bullet collisions
- construct volume to build points from by subtracting the mug volume from the base volume to avoid beans interpenetrating mug.

Quick question... June 12, 2019, 9:20 a.m.

vex functions opfullpath()and relativepath() return paths to nodes.

http://www.sidefx.com/docs/houdini/vex/functions/opfullpath.html [www.sidefx.com]
http://www.sidefx.com/docs/houdini/vex/functions/relativepath.html [www.sidefx.com]

Here's one way to use opfullpath to return a string node name:
s@pathfull = opfullpath("../timeshift1");
s[]@pathsplit = split(s@pathfull, "/");
s@nodename = s[]@pathsplit[-1];
Just replace the s@pathfull and s@pathsplit to internal variables to avoid attribute bloat. Just exposed for clarity.


Now I have to ask, what are you doing?
It isn't that efficient to fetch a single node name for all the data/points you are ripping through.
If you have unique nodes to apply to different items you are processing, sure. But strings aren't the most efficient method through vex for lots of data processing.

It may be better to put a local spare parameter on the node and build out the string once as a set of parameters when the node cooks.
Python is very powerful at string manipulation while in vex it is somewhat limited…

Particle Lifetime measured in seconds? not for me! June 12, 2019, 8:31 a.m.

I would first check in DOPs to see how the attributes age and time relate. In DOPs this is the geometry spreadsheet in popobject/Geometry.
If you cut your lifetime to say 2 and then play forward you should see age reach 2 then particles die.

In SOPs you can distort time. Time Shift and Time Warp SOPs come to mind. These would cause the age attribute to not reflect time…

How did you set up your particle sim?