Hi @fn75372,
To echo @FAXCORP, yes, the solution will be to attach the niagara system to your camera component and change your system to local space (you can just click on the entire emitter and it will be the first option. It’s hard to tell if you’re doing this in the screenshot, but make sure when you attach and offset, you also control the rotation so the system is always facing the camera along the X and Y axises (it looks like you might already be doing this anyways). This will make things a lot easier in the future and avoid you having to mess with matrices.
However, this problem may be more complex than you realize, as you will have to account for different monitor sizes if you always want them to appear on the edges of the camera. To get the particle bounds, grab the viewport size from your blueprint, then input it as a new Niagara User Parameter. When you set your plane/box size, you can input your user parameter.
If you are offsetting from the camera, you’ll need to add a multiplier, and you can continue to use this Vector 2D for masking the inside of your effect and such.
Another side note- if your effect needs to have some depth to it, I would recommend faking this through particle size. If for some reason you can’t use this method, be aware that your particles further away will not take up the entire viewport due to the 2D to 3D conversion of a box. You can get around this by using Slabs as your shape type, though this gets a little more complicated so let me know if that’s something you need and we can go into it then.