How to Spawn and remove Particles based on an Animated texture

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  09 September 2013
How to Spawn and remove Particles based on an Animated texture

Here's the scenario, I want to use a Position Object operator and spawn my particles based on an animated Noise texture in the volume of the object, but it seems that the Position Object only evaluates the placement in the first frame and will not update the spawn position throughout the animation.

Is there a way around that?

Please note that I'm trying to place my particles in the volume of the object and not the surface, so the Birth Texture operator won't work, unless I've missed something.

Also speaking of Birth Texture operator, it seems that it only spawns particle when using an animated grayscale textures, it does,'t remove them based on the grayscale value, so it doesn't really conform to the animated texture which is kinda odd, (but I'm sure I'm missing st here.)

So what I want to know in the end is how can I animate the spawning and disappearance of my particles based on an animated texture, both in the volume of and object and on it's surface?
 
  09 September 2013
Well Pflow is a little more basic structurally than you think. Operators and Tests typically only do one thing. For instance there is now Birth/Delete operator in one. Unless you make your own with a Data op (save that for later, learn the basics first)
Quote: but it seems that the Position Object only evaluates the placement in the first frame and will not update the spawn position throughout the animation.

Correct and since you are using volume their is nothing to attach the position too. If it did have a reference position how would the operator know which direction to move it? Thats is what speed/direction based operators are for.

Quote: Also speaking of Birth Texture operator, it seems that it only spawns particle when using an animated grayscale textures, it does,'t remove them based on the grayscale value, so it doesn't really conform to the animated texture which is kinda odd, (but I'm sure I'm missing st here.)


It is a Birth operator not a Delete operator. Why would a birth operator delete particles?

Quote: So what I want to know in the end is how can I animate the spawning and disappearance of my particles based on an animated texture, both in the volume of and object and on it's surface?

You can create a Data operator to delete based on greyscale values. (I know I told you to learn the basics first but this is the only way to easily achieve what you are asking.)

Quote: So what I want to know in the end is how can I animate the spawning and disappearance of my particles based on an animated texture, both in the volume of and object and on it's surface?

Well can't really give you an example without actually doing it for you. See attached.
Attached Files
File Type: zip max2009_PF_BirthDeleteByGreyscale.zip (23.7 KB, 19 views)
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  09 September 2013
Thank you very much Johnny, both for the info and for the sxample scene as always, Yes it makes sense, actually I came to realize that after posting this, that I shouldn't probably expect a birth operator to also be able to delete the particles, though in the case of something like the Birth Texture it would've been a nice feature for scenarios like this.

A few questions about your Data Op, can I ask why you did a reverse condition in the end? I've seen this being done before, is it so you can get a '<=' result?.. Another thing(and it's also apparent in my own version) I just can't get a smooth result from this, no matter if I cache it or not or how I cache it, the animation of the particles aren't smooth, is there any way to get a smoother transition in there?

And while I was waiting for answers I started tackling this in a different way, basically I used the Birth Grid Op, create a grid of particles inside the volume of my shape, and used the Data Ops to control the Scale of the Particles instead of their existence(hehe), it's not exactly what I was asking in my first post but it kinda does the trick for me, though still there's the issue of the jagged playback, which I was talking about.

Here's the file in case anybody's interested.
 
  09 September 2013
Nice, yep Birth Grid is super handy for uniform voxel grid based stuff.
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  09 September 2013
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