Hey people,

any idea what the time measure for Particle Lifeexpectancy is? The documentation says it´s measured in seconds, but for me it´s not… is there an overwrite somewhere in the Project settings?

Thanks for your answer

cheers Linus

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?

thank you for replying.

I setup a very basic Autodop network since I am just learning the particle system in houdini:

I would like to have “floating” coffee beans around my CoffeeMug. So here is my thought:

1) create a thin Volume around my mug -> I polyextruded a Tube
2) fill the Volume with points -> points from Volume node
3) feed the points into my autoDopNetwork to generate Particles on these points.

myProblems:

a)generally: I am missing still some knowledge which attributes are mandatory for a sim to work, and where they have to be defined.
b)specifically: I cannot find the age/time relation that you mentioned earlier.
c)on particle generation right now, the particles(CoffeeBeans) are somewhat snapping from an initial position to their actual destination on the volumepoints - I have no clue where I can fix that. (—> okay I found out that the “offset” is caused by the AxisForce node that I forgot to mention)

maybe you can point me to a good tutorial on understanding the basics I mentioned above;
that would be a great help.

… so I found the missing link:

1) The Popsolver has a timestamp which was set to 0.2 —> after adjusting that to 1, my Lifeexpectancy is exactly what I set it to in my Emitter Source Node.

2) still couldn´t find what causes the spacial offset of my particles in relation to my points, but the “snapping” was caused by the AxisForceNode I applied earlier.

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.

Thank you very much, for me that is a deep insight into how other artists aproach the same problem differently.
thank´s for taking your time.

old_school
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.

Would you please elaborate on those two nodes in your Setup?
What do they do?

And why can´t I just use a RigidBodyObject in the DopNetwork and reference it to the Mug itself on SceneLevel - is it because the animation doesn´t update on each frame?


Thank you,
Linus