Spark particles based on trails cause shadowmap shadow to flicker

Bug Reports Engine Bugs
#1

I wrote a particle spark system some time ago, and since then using shadowmap started causing flicker whenever the particles are emitted;
https://gyazo.com/34c234180385871abe9b31b161c7ce4b

The effect itself is essentially small neon trail parts coupled with a pointer object, and a tracer part being destroyed right near them. ALL trails have light emission set to 1 and particles generally hover between 0 and 1.

It happens both in studio and ingame, and is not affected by the trails inside of the sparks (deleting them changes nothing, there is basically nothing able to emit light to the shadows aside from trails, and disabling the particles fixes it every time)

Affected game:

Specs:
Windows 10 home/pro, and a 970 and a 750 Ti (i had both windows editions and cards, all of which had the same issue)

Assets used for the effect:
items.rbxm (6.7 KB)
Community feedback:
image

5 Likes
#3

It’s worth noting that this can’t always be reproduced, even in the same place. I wasn’t able to reproduce it myself with the following specs:

Windows 10 Pro
GTX 1660 Ti (also tried Intel Integrated Graphics 630)

2 Likes
#4

I’m having this problem too. I have a rain system which uses trails for raindrops. It uses a module called PartCache to improve performance. It’s strange because if I remove the cache and just :Clone() and :Destroy() brand new raindrops it does not happen.

When a raindrop is returned to the cache it will hide it by setting it’s CFrame really far away (0, 10e8, 0). For me atleast, it appears that the flickering intensity depends on how far away my raindrop is CFramed when it is returned to the cache.

A position of (0, 5e8, 0) produces less flickering and at (0, 1e8, 0) there is no more flickering.

10e8 height:

5e8 height: (Less widespread and intense flickering)

1 Like
#5

Same problem here, it’s a really weird rendering issue! I’m using PartCache as well, and it does not cause any flashing if you change the cache position to something below 1 billion studs away from origin. Any higher (around 2B) and it occurs. Most of the focused map will flicker each time it’s brought in. Doesn’t specifically relate to Trails/ParticleEmitters it seems, but is mainly caused by the part being moved from so far away.

This happens in every lighting mode except for Compatibility.

Here’s my system information if that should be provided:
CPU Intel(R) Core™ i7-9700K CPU @ 3.60GHz
GPU NVIDIA GeForce GTX 1050 Ti
Memory : 16.0GB

I’d be happy to send a repro file to any engineers that need it privately, I’d rather not share it publicly here at the moment.