Inherit velocity in DOPs

[ChristopherC]

Hi there!

 

I hope it's ok to turn my first post into a question?

 

For a quick introduction, I've been a character rigger for ~10 years (showreel), I'm quite versed into programming, and I've recently started to learn FXs using Houdini which I find to be pretty damn cool!

 

As for my question, I'm aiming to have a wall being hit by some *invisible* bullets. Each impact would be triggered manually, would create a hole in the wall, and would get some debris flying off.

 

For this exercise, I want to be able to have a full artistic control on the shape of the impacts and the direction in which the debris pieces are going to fly. As such, I've been adding a custom velocity to the points of the impact geometries, transferred them onto the `RBD Fractured Object` node using the parameter `Inherit Velocity from Point Velocity`, but it doesn't sim as expected. If you visualize the velocities from the scene attached, you'll see that the red impact has a +10 velocity on the Z axis while the green one has -5 on the Z axis, but when simulating it seems that they're both being averaged into a single velocity, and all the pieces fly in the same direction.

 

I've noticed that Bullet created a single convex hull containing all the pieces from both impacts, which could explain this behaviour, but I thought that checking `Create Convex Hull Per Set Of Connected Primitives` will be enough to fix it? I guess I could create one `RBD Fractured Object` for each impact, but then how would I go if I had 300 of them?

 

What am I doing wrong?

 

Cheers!

inherit_velocity_in_dops.hipnc

Edited February 13, 2015 by ChristopherC

[sadhu]

1)In obj wall  after foreach1 sop add attribute sop and delete name attribute.

2)Then add assemble sop to create name attribute again.

Now pieces will start going in the desired direction.

 

I think in foreach sop for the first iteration(red colored geometry) it is generating pieces with name piece0 piece1.....    and it is doing the same thing for the second iteration(green colored geometry,again generate pieces but with same name value piece0 piece1 ....), so each name value is having two geometries (one from red and one from green colored geo ) 

 

hope this helps.

Edited February 13, 2015 by sadhu

[ChristopherC]

This makes perfect sense, thanks for your help!