There’s a nice way to make a jet effect using rectangular particles. What you do is make them tall and thin to start with and then you return them to a square shape at the end. This prevent gaps from forming in the thinner part of the jet without needing to use too many particles.
The problem is that you see a lot of repitition because you need to keep the particles at the default rotation or you’ll break up the line. What I’ve used in other particle editors is a a couple of check boxes to randomly flip the X and Y UVs of each particle randomly when it spawns. This gives you back some variation without having to mess up your rotation. Is there a way to do this?
Currently there is not a way to do this as you have requested in Cascade.
One option you can try is to setup two sets of texture coordinates/textures and on one set one of them check Un Mirror U and Un Mirror V.
Lerp between these coordinates using one of your particle color channels, and a uniform distribution on initial color set to 0,1 with the use extremes box checked.
You can try using the dynamic parameter, with the spawn time only box checked and min max set to 0-1, but there is no use extremes box, so you can get values which are between 0-1 which may look odd.
Just to update the answer to this. I was also looking for a similar functionality (even posted a request), and found an option in Cascade’s Particle System Required module under the Rendering section called UVFlipping Mode