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Emit with velocity relative to particle

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Simon Russell
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Hey,

So I've got a particle system that emits particles from a main stem. They emit at 137.5 degrees per particle (golden ratio) along the XZ plane. This is what's happening in the uploaded file and works ok.

But now I want to emit another set of particles from those sub particles but not on the XZ plane but relative to source particle. In the same 137.5 degree pattern.

Any help would be greatly appreciated.

Thanks

Attachments:
Relative Velocity.hiplc (273.9 KB)

http://simonfarussell.com [simonfarussell.com]
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Simon Russell
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Here's a sketch that helps illustrate


I suspect it maybe a pop wrangle solution. Maybe a matrix multiply but I can quite figure it out…
http://simonfarussell.com [simonfarussell.com]
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pezetko
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Just prepare your velocities before emitting then inherit them directly.

See the file.

(edit: added degree to radians conversion)
Edited by - May 2, 2015 12:59:59

Attachments:
Relative Velocity.hipnc (368.3 KB)

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Pasto
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Hello,

I also had to get velocity from sop, I could't find a way to control it with a POPvop, it seems to “set” the vel at each frame.

My file is quite clunky I guess, I don't know how to preserve a nice regular gold angle flow.


Pezetko your file is much more advanced.

Can you explain briefly how did you prepare the velocities ? Especially the quaternion and cross product combination ?

Many thanx anyway.

J

Attachments:
Relative Velocity.hiplc (362.9 KB)

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pezetko
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Hi Jerome,
it's not my file, I just added single attribvop to prepare velocities (the green one) and removed circle (sin/cos) expression from pop source of third pop net.

I basically did same thing like you did.

I took normalized velocity and set it axis for rotation. Then I took vector perpendicular to this axis (result of the cross product) and rotated it around that axis by $F*angle (137.5 or whatever you want). This axis and angle (converted to radians (fixed filed is uploaded - I missed this in original file)) defines quaternion. That one is used for rotating that vector along branch and fed into new velocity.

Rest is normalization and speed maintain to keep everything correct.

Attachments:
Relative Velocity.hipnc (368.3 KB)

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Simon Russell
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Thanks guys. Both very interesting solutions.
I certainly have a little bit of studying to do to fully get my head around your solution Pezetko. I'm not familiar with Quaternions.
Very much appreciated.
http://simonfarussell.com [simonfarussell.com]
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Pasto
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Thanx for the explanation pezetko, I will study the file.

J
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