Fade out trails

[recording-team]

I've got a scene with a number of particles and trails and I need the trails to gradually die out and fade from the stage at some point after they first appear (say, fade out for 90 frames after 150 frames on the stage). I tried the Properties/Lifetime parameter but that just freezes the trails at their current position (at the frame specified in Lifetime). Is there some way to get the trails in this scene to fade away after some number of frames? Basically, it would be like a "lifespan" parameter but with an adjustable "fade out time" setting.

The scene file is here: https://www.dropbox.com/scl/fi/pmg3m7b9s04mhrna5wv0g/will-not-die.c4d?rlkey=wa7fra9e88h44txbcjjkrs1wl&st=6dq7jf3k&dl=0

Thanks for any info.

[Dr. Sassi]

Hi recording-team,

The trails are based on a Tracer, which means a Spline is created based on the particle's position per frame. This is no longer part of particle information at that point. Hence, it has no idea about the data on any particle.
The idea is to use the Spline Emitter.
The material needs to have user data RGB+A enabled, and the color mapper needs to be set to change the alpha information over time.

The Tracer must be set to be short – From End, perhaps 3 Frames, while the Spline Particles have zero speed.

Example:
CV4_2025_drs_24_PAsa_11.c4d

All the best

[recording-team]

This looks great. Just can't sort which param will allow the traces to last a few hundred frames longer before dying out. Tried the Color Mapper Age Property setting and the Lifetime. but neither allow the traces to persist so they stretch out a bit. Is it supposed to be one of them? Thanks for the info.

[Dr. Sassi]

Hi recording-team,

Please have a look at the file below:

CV4_2025_drs_24_PAsa_12.c4d

🔒 Log in to view

The max-age is set to 600 frames. The Alpha gradient starts at 83%, meaning at (age-based) frame 500, and the total fade is after (age-based frame) 600.

All the best

[recording-team]

Thanks again - much appreciated. Still not quite getting the initial length and form/look of the particles before they fade as shown here from fr 376 of my original:

https://www.dropbox.com/scl/fi/g6jcbw3rywo5rhsfxq78z/ideal-tracer.jpg?rlkey=v0a2jbnup7mmfqz17s8lny046&st=qiwa10c3&dl=0

versus fr 376 of the edited version: https://www.dropbox.com/scl/fi/l1dmib0z6171aj51eiuf1/edited-tracer.jpg?rlkey=9jr5f9h19pi2e73pi77z7zqew&st=0ublpdwj&dl=0

Quite a difference in the appearance of the tracers, et al. Can you think of a way to get the duration of the fade length and the amount of fade out time as well as the original appearance of the tracers? And I'm not exactly clear which params I need to modify for those two settings - if you could point me to both of those that would be great. And thanks for the effort in any event.

[Dr. Sassi]

Hi recording-team,

I'm sorry, but I have no idea how to get either Tracer Material results to respond to time-based settings, as they are not stored, or particles to grow on several Tracer Splines separated by colors. Here, we want to have a single color per spline. This is your target, correct?

The practical way would be to store each Pulse in a new Particle Group and get the Tracer Spline results in separated groups as well, each as one object, which can have a copy of the material and adjust the fading with a few keyframes. In this way, you have full control. Is that much more work? Yes.

Is that more work than searching for a workaround to get time data to splines while keeping each Tracer Pulse result colorful based on a Ramp? I doubt that this is faster.

Do I believe it is impossible at all? There is always a way; the question is only what is more work and what is easier to art direct:

However, perhaps this helps the demo render:
https://www.youtube.com/watch?v=Hd3rAcNRg3M

Discussed here:
https://cineversity.forums.maxon.net/topic/1256/color-change-color-mapper-tracer

Enjoy the exploration.

All the best

[recording-team]

Thanks for your reply and the link. I guess this involves more techniques and is more difficult than I am understanding. I just wanted the particles/tracers as seen in the first scene file I sent - those color and shapes (and sizes and positions) to fade out after a set amount of time on the screen- paint around the screen, then fade out. Something along the lines of the "birth" and a "death" rates in XP is what I was thinking of. But what you sent has quite different colors (and some sort of bloom) and the traces are much small overall... wasn't sure if some parameter or other got tweaked that might not have. I need to try and duplicate the fade to alpha gradient from yours i my original without changing all the other traits (color, size, etc) of the scene...
If you don't see any way just to make the tracers fade out while in the positions in which they appear in the original scene file, then I guess we need to move on. Might suggest the devs consider a "fade out" parameter/force...
Thanks again for the help.

[Dr. Sassi]

Hi recording-team,

Particles can fade out by setting up an age-based gradient for the Alpha channel used inside the material.

Let me try again: The MoGraph Tracer does not have any idea about time, more precisely, age. Without this information, fading is not possible.

The workaround initially shown can't produce the same color on a single spline. So I created a new material, with a different color that is supplied to every single one in the same way.

So, you say that X-Particle has an option for Splines to fade out based on age?

If you like to suggest features, please do so here: "Share your ideas."
https://www.maxon.net/en/support-center

All the best