RBD State Question

[galagast]

I'm following a couple of small exercises from this website:

http://houdinibasic.blogspot.com

I realize that it is quite old (Houdini 8.2), but I decided that it could be a challenge applying the exercises to Houdini 12.5 as part of learning.

I'm currently at Exercise 20, and I got curious about the RBD State.

This is the current setup:

The tutorial used a Copy Objects DOP which created 5 copies, but it never assigned position values for those copies, that's why I added an RBD State DOP (I got the hint based on the sample at the help file).

My current concern is:

• Whenever I turn OFF the RBD State DOP, my Boulder object would fall down in just a few frames
  
• Once I turn ON the RBD State DOP, the copies falls down a lot slower.
  

Essentially, I was expecting that the rate at which the objects falls would be the same regardless if the RBD State DOP is ON or OFF...

The purpose of the RBD State SOP on my scene was just to randomize the positions of the copies.

Any hints/help would be appreciated : )

Houdini 12.5.376

houdinibasic_lesson20.hipnc

Edited May 7, 2013 by jlim

[sho]

I guess your setup is currently overriding each boulder's position every frame due to "Set Always".

Try setting $ST == 0 in Activation parm of RBD State node. It'll run your expression only at first simulation time.

[galagast]

Awesome! That fixed it! Thank you so much.

Earlier, I thought "Set Initial" was somewhat the equivalent of $ST == 0.. but it was not doing what I was expecting it to do.

"Set Initial

Set the value of this parameter only when this data is created. On all subsequent timesteps, the value of this parameter is not altered. This is useful for setting up initial conditions like position and velocity."

Thanks again Sho-san, arigatou gozaimasu.