Containing Thinking Particles Within A Model

[Adam Trachtenberg]

You should be able to keep the particles in the volume using a pdeflector node. You can control the speed of the particles with a pvelocity node.

For the last question, you can get the position and alignment of a particle using the pgetdata node. The only way I can think to isolate a particular particle would be to place it in its own group. One way to do that would be to use a collision object to trigger the group change. So, maybe place a small plane in front of the particle in question, set it as the reference for a pdeflector node set to “event only”, and use the event out port to trigger a pgroup node. Then you could get that particles position/alignment data and use it to drive the position/alignment of a separate object.

[Joey Campbell]

Thanks for your help Adam – I tried adding a pDeflector node (see attached). Unfortunately the cells kept moving through the artery wall. In case it was an issue that my artery model had a gap in the side of it I experimented using a solid cube stuck in the middle of the cells path and used that as the deflection object…no joy there either. I also tried using dragging in different particle layers and even leaving the particle layer blank. Could it be anything to do with the fact that the cells are following a path or that the cells have their own separtate particle collision ?

I’ve also highlighted the location of the existing point velocity node in the ‘follow spline’ section the cells are following. Can this somehow be tweaked to make the cells move forward in ‘rushes’ (ie like how you would use an after effects expression ?).
Cheers
Joey

[Adam Trachtenberg]

It’s really hard to tell from the screen caps. Those TP presets can be very handy, but I find them quite hard to decipher if I want to make changes to them. You’ll have to go into the Xpresso editor itself rather than relying on the provided user data inputs.

For example, if you open the Xpresso for the object collision preset and click on the PDeflector node, you’ll see that the type is set to Front, meaning that particles only collide with polygons that have front-facing normals. Your artery object probably has the normals facing out so the particles are passing through. Change the node’s type to Back or Both Sides and it should work.

[Joey Campbell]

Hi Adam – I just reduced the diameter of the particle flow as a quickfix. I’m going to go back to basics and learn TP from scratch next week. It seems like a really useful tool but trying to learn it by reverse engineering a pre-existing animation is a but too ambitious!
Thanks for all your help.
Joey

[Adam Trachtenberg]

I think that’s a good idea. Personally I know just enough TP to be dangerous. 😉

[Joey Campbell]

Hi Adam very last question on this issue (I promise!).
Like I mentioned earlier – I want to start off looking at an individual cell within after effects (it will be a rotating .obj used within Form in AFX). From there I want to seamlessly transition to the bloodflow of all the particles. Is there anyway I can get the coordinates of the particle of the TP cell on the left so that I can apply them to the model/obj cell on the right (without going near TP or xpresso)…or plan B…is there a way to right click on a duplicate of the TP particles and convert the to a static mesh whereby I could then isolate a single cell and export it as an obj ?

[Adam Trachtenberg]

The easiest way to do it, IMO, would be to bake the TP animation with Nitrobake (paid plugin). That way you could reduce to the particle animation to real objects and real keyframes. In this case you would simply delete all of the baked particles except the one you’re interested in.

Another option would be to use mograph to clone onto the TP particles and then bake the mograph animation (see Youtube tutorial(s)).

[Joey Campbell]

Thanks Adam