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Size by Speed on Particles has no Effect

I'm having trouble getting size by speed to to work, I have a simple particle system with drag so it slows down over time. I'm expecting the particles to start big and shrink as the speed decreases, however they stay the maximum size the entire time. Is there a step I'm missing to get this to work? Thanks

This is my setup

Product Version: UE 4.10
size by speed.png (62.4 kB)
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asked Dec 10 '15 at 05:03 AM in Using UE4

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avatar image Mighty Marcos Jan 19 '17 at 12:57 PM

I'm not sure, but... I think you should check if the screen alignment (in the required module) is set to Velocity. Take a look to this tutorial, it might help you! https://www.youtube.com/watch?v=7hC_QT4GLiU∈dex=4&list=PLZlv_N0_O1gYDLyB3LVfjYIcbBe8NqR8t

avatar image zaknaf Jan 19 '18 at 12:37 PM

This unfortunately doesn't answer posters question at all. Just wanted to save others from wasting time. Appreciate you trying to help Might Marcos. Particles in that video do not shrink when their speed drops.

avatar image Mighty Marcos Jan 26 '18 at 12:44 PM

Growing or shrinking is not a problem, as its basically the same thing! :D

That video shows how to relate the size and the speed of the particles, so tweaking a bit the values of the scale you could achieve that without issues.

I mean, instead of setting its value to 6 (as it does in the video), you could set it at 0.6. If you do this, the particle should shrink instead of grow. Do this with both vectors(X/Y), and voila!

I don't know what kind of particle wants bigdunk15 to make, but if it's something, I better recomend to use the SizeByLife module. Unless it's critical to asociate the size and the speed,Ii think it will give you more control over your particle scale!

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Oh, I think I missunderstood the question, and I'm sorry for that!

So... I think that the Size By Speed module gets the velocity of your particle at a specific time, and multiplies it by the Speed Scale parameter, and by the actual particle size. This may make it difficult to get the default scale of your sprite.

For example, if your particle has a speed value of 1, an initial size of 1, and a Speed Scale value of 30, your particle actual size will be of 30 (all of these, of course, in a specific axis). So, if you want your particle to get back to its size value of 1, it's speed should be something like 0'03.

It's a bit messy, and I may not have expressed myself as clearly as I would like, but you'll have to play with these three values over time to get the desired effect.

Hope this one finally helped!

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answered Jan 26 '18 at 01:00 PM

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Mighty Marcos
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