Jump to content

Recommended Posts

Hello everyone...  I have a problem with an RBD packed object inheriting velocity.  In the file, I have the attribute active being set by another object, but the velocity doesn't kick in at all.

The velocity works if I remove the point wrangle setting active to 0 and remove the sop solver.  
If I try a pop vop or a geo vop, there's some weird velocity behavior that happens.
If I tick on override attribute, the velocity takes off big time and doesn't appear that gravity takes hold.

All I'm looking for is initial velocity once the pieces become active.

I saw a few threads on the side fx forums and this forum, but nothing I saw seems to be working.


Any thoughts?


Link to comment
Share on other sites

Hello Neil,

Unfortunately something changes in the latest houdini versions about the inherit velocity from pack objects, a working way for inject the velocity only at the activation frame it's creating an attribute containing the previous @active value ($F-1), and add that to the "override attr from sop" inside the rbdpackedobject. That field should contain (@active and the created attribute containing the previous activation value ---> @prev_active) then with a geometry wrangle or pop wrangle it's possivle comparing the two attributes and gather the velocity to inject only if those two attribute are not the same with a point expression. I'm interested however if there are other ways for doing that, somebody have any idea?

--Cheers Dam

Edited by Dam
Link to comment
Share on other sites

@Dam:  When I was looking at the spreadsheet in the DOP network, I noticed using the active attribute that the velocity was being reset as opposed to when I didn't explicitly define that attribute and using the sop solver...

@Varishtraheja:  Not what I wanted.  The animation needs to break apart like it's being affected by wind.  Look at this:  


Link to comment
Share on other sites

Not sure I've understood your scene so take this with a pinch of salt. But, it looks like you're trying to transfer both the velocity attribute and the active attribute of the active object to the inactive ones. To do that I calculated the velocity on the active object using Trail SOP and then in the attribute transfer in the solver also transferred the velocity. Probably not what you meant!


Link to comment
Share on other sites

@julian johnson

I looked at the file, it wasn't what I was looking for....for whatever reason, it's not keeping the initial velocity on the pieces when they are inactive.

I want the velocity to take off as the objects become active.  It doesn't matter whether I inherit velocity or even use the velocity on the rbd packed object to do it, it just won't do what I want.

Edited by ntkirby
Link to comment
Share on other sites

@julian johnson - I saw the post here so I decided to try it.  It worked, so I went ahead and tried some other things outside of using wrangles to see what I could accomplish and I get some odd results.  I'll take a look at his H16 file and see if anything else is going on...I'll check yours too when I get home.

Link to comment
Share on other sites

  • 4 months later...
On 20/9/2017 at 7:07 AM, julian johnson said:

That's a great new feature. Far less elaborate than before. So, now as long as you set the initial state to active 0 and animated 1, you can switch to active at any time, turn off animated via attribute transfer in SOPS and the objects will inherit velocity at any frame.


 thats an elegant solution ;)

Link to comment
Share on other sites

  • 3 years later...

Hi Guys,

I am in the same situation but in a different way, the thing is my fractured pieces have constraints on it which I am breaking in dops, bringing in the velocity in thru sop is not working as it keeps on adding every frame.

How can I get the initial velocity which I am setting in sops to work in this case ?

Would really appreciate if anyone can help me with this.




Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...