I'm trying to output a project 1920x1080. I've set the stage size to those dimensions, and also the default size. The fields next to Stage Size keep switching back to 320x240. It outputs a file that is 1920x1080, but the PI image is 320x240 in the center of that area. How can I get it fill the raster? PI 18.104.22.168
In the project settings dialog you'll see a box for stage width, then one for stage height, then a pulldown menu with a list of common sizes. The width and height boxes are what matter -- the menu is for faster setting of the size you want.
So if the pulldown says "320x240" but the width box says "1920" and the height box says "1080", 1920 x 1080 is the size.
Are you using a background image for the layer, or is it only particles? If it's only particles, I don't know why it would be using only the center 320 x 240.