Particles not visible in exported transparent png from Movie Render Queue

Hello! I am trying to use the Movie Render Queue to capture some particle effects as an image sequence; a png with transparent background. With “Accumulator Includes Alpha”, the particles are fully visible in the rendering window, but are not included in the images. They are only visible if there’s an opaque object behind them.

example of a cube placed behind the particles.

So are you rendering them with alpha to be composited? If they’re white and have alpha you will need a darker background for them to show up (or some type of contrast/color difference

Honestly I don’t really understand what you are saying because I am not familiar with this terminology.
I don’t know if “alpha to be composed” is a certain technique or setting that I should be doing that I am not doing.

For clarity I’ll take a screenshot of Kritas checkered background that indicates alpha. I hope these can speak for themselves.

Alpha means there’s a mask as shown in your image of the cube.
It doesn’t appear there is.

In Unreal make sure you turn on alpha in the project settings.
Engine Rendering → Post-processing enable alpha set to linear color space only.

Double-check render settings in the movie render queue for any alpha controls and make sure to output 32 bit if that’s an option. You could also render in EXR format with multilayer off since that will have a real alpha.

I’ve never rendered particles as a separate element so there may be a Niagra control involved as well.

Okay, I changed from “allow alpha through tonemapper” to linear color.
The only setting in the Movie Render Queue I change is enabling “accumulator includes alpha” under Deferred Rendering.

exr (16bit) ( all 3 compression options and multilayer unchecked)
does not display particles unless cube is behind.

png (8bit)
does not display particles unless cube is behind.

jpg (8bit)
does display all particles, but no alpha.

I’m testing with the cascade PS system in example content, P_GPU_particles_attraction2.
I added a Niagara template Simple Explosion, which does not show sprite particles, but does show mesh particles.

I would suggest posting un Niagara and visual effects. There might be a setting for particles to render alpha properly.

I’m searching for the same answer, I have a work around , change translucent material to masked material , insert a dither temperal AA node before opacity port, output higher resolution image with high samples , but the dithering effect is not a perfect solution, so I still want to know the proper way.

Hey @ste1nar wondering if you’ve managed to find a solution for this? Facing the same issue on my end as well

Managed to render Niagara with Alpha using Stencils. Here is a helpful tutorial: Why You Should Be Using Stencil / Render Layers - Unreal Engine 4.26 - YouTube