Hi, I added the speed lines from the node library to the scene and already figured how to change speed, positioning, thickness and that stuff.
But how do I reverse their movement?
The speed lines are currently moving from a certain point outward, but I want them to move from the outside TO a certain point - so simply reverse them since the camera in my animation is quickly zooming out.
Any suggestions on how to achieve that? Am I overlooking something?
Thank you!
Noone? 
You can select all the frames of your animation, then Cut (Ctrl + X), then right-click on the timeline and select Paste Reverse to reverse any animation. 
Thanks for the reply. That’s indeed how I’d usually do it but it seems that won’t work with particles.
When I select the all the frames of the speed lines, cut/copy them and choose paste reverse, they still move in the wrong direction.
So nothing has changed.
I have not worked with this and do not have a moment to check but have you tried using a negative number?
Yes I did, but it always ended up in a mess (they sometimes moved straight from left to right, or weren’t visible at all, so no success here). I start to believe that the velocity node (that was there by default when I added the speed lines example from the library) is just not the right thing for what I’m trying to do.
However, I tried a few other of these action nodes instead (like vortex, orbit etc.), but I’m still struggling with reversing the speed lines.
The default way its set up there’s no way to reverse the lines. You would have to rebuild it with the outer ring of planar region being outside of the camera and with a sink in the center.
Okay that sounds like a step forward, thank you. However I’m afraid I still don’t get it managed, I tried to add a planar region, set it to “disc” to make it a circle, increased the radius to keep it out of screen and added the sink node as you said. But it seems the latter doesn’t do anything.
Sorry for asking, but since you seem very familiar with the particle system, would you mind setting it up in a quick way and send it over (or make a screenshot)?
There’s no need to make it look good or anything, it just has to work basically so I can pick up from there. I would be so grateful.
Not sure of the details in the scene you are working with but just thinking of the speedline animation you could render it to images then reconstruct the sequence in reverse using a video editor.
Particles are a bit tricky, especially in terms of the 3D space, if you want any sort of interaction with a character, etc. The speed lines example is not real 3D. If you try to rotate it you’ll see it’s not really moving towards the camera. As is was mentioned by vrexus, there’s no direct reverse option because you can’t generate particles towards the region connected to the Sprite-Emitter. The easier solution, if you’re pleased with what you have and just want it inverted, is probably what o0Ampy0o mentioned. You can render the particles with alpha, then reverse them. You can import the Quicktime directly to Harmony, then paste reverse or reverse it in another software before importing.
It seemed easier to me to try to do something like you want based on the Rain example.
You can check it here: https://www.youtube.com/watch?v=tg_l_fmFMEo
Basically, I moved and rotated the Planar Region connected to the sprite emitter so that it would generate particles behind the camera instead of over it. In the Velocity module I put 0 on X and Y and -1 on Z. You can change the Sprite with the actual drawings (I just made the rain drops more like lines, you can, naturally, make any drawing there) * and the colour on the colour palette. You can change the size and position of the Sink, which is the area in which the particles are allowed to exist. Note that it’s not perfectly realistic in terms of 3D perspective as it is.
I suggest reading the documentation on particles and play a lot with the examples. If this example I made is useful to you I can send it as a template.
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Luis Canau
Hi Icanau, thanks for the helpful explanation. The animation of yours is almost perfect and exactly what I need. Just a few questions beforehand:
will I still have the possibility to move the center point? Because at the beginning of my animation I need it to be in the upper left corner.
And while most of your particles move perfectly according to their perspective, some of them don’t. Is there a way to fix this?
https://s29.postimg.org/495x3677b/Screen_Shot_2017-04-21_at_14.41.25.png
Yes, I’d really appreciate getting the template. I’ll try everything out then. Thank you!
Yes, that’s why I mentioned it was not totally realistic The problem is particles being generated in the centre. That can be improved by creating a matte and connect it to the Planar-Region (changing the Shape Type from one of those generated by Harmony to “Image” and attaching a drawing to the left port).
In this example, I created a circle with a hole in it so that particles would not be generated exactly at the centre: https://www.youtube.com/watch?v=L-apkNfZtHM&feature=youtu.be
To offset the centre, I changed the X and Y values to 0.2. You can play with those parameters to change the direction of the particles. There’s always other options, this seems to be the most simple to me.
Here’s the two versions: https://we.tl/d9KQ4MSFqL
Just unzip it and copy to one of your template folders. Maybe you can just use the first one and change it to your liking.
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Luis Canau
Hello! I have the same problem… can it be done with a vortex particle system too?
New question.
Originally, since the camera in my animation is quickly zooming out, I needed those speed lines to be reversed. Thanks to you Icanau, I got it managed by using your template.
But now it’s kind of a different story. The way the animation has processed, I’ve made the camera zoom out (speed lines move inwards), then turn around and then zoom IN. Which means, this time I’ll need the “speed lines” to move outwards again, just like they do when you simply drag the speed lines example node into your stage.
So I COULD just use the speed lines node, as I tried back when I created this topic.
But it’s not that easy. The issue I’m having right now is, that the speed lines aren’t supposed to be speed lines this time, but bubbles. And I don’t only want them to move outwards, but also become bigger the closer they are.
I tried two different things without success:
• At the moment, when I use the speed lines example node from Toon Boom, and just replace the speed lines drawing with a bubble drawing and disable the blur effect, I can see the bubbles floating, but they’re always the same size.
• I took your template (the one with the circle in the middle and the sink node), which perfectly adjusts the size of the particles according to their distance. But I couldn’t figure out how to reverse them to make them move from the inside out. I tried to mess around with X,Y and Z axis, positionings and stuff (I literally checked every properties window I could find in your speed lines template) but I didn’t get it.
I’m hoping I could describe my issue in an understandable way. Find my project file attached, it would be great if someone could take a look.
Once the camera has turned around, I want the bubbles to move just the way they do at the beginning, but reversed.
Thank you!
Anyone?
The easiest method would be to render out, and then reverse the video in video editing software, as mentioned previously. Many times you will find this to be an easier solution when it comes to computer generated effects simulations.
Okay, will try that. Thanks!