Strictly speaking if you really want 3d effect, the PPI won’t be enough. You can certainly vary a bit, but you don’t get real depth. You either hit a spot with some photons or you don’t with the M2. PPI is going to maybe do shading but not actual physical depth.
That’s not to say there’s not a solution. Just that it’s a bit weird. What you want is a z-raster. Various people have come up with this before but basically you raster over the stamp not once but several times. You might need some practice to get this right, but if you right click an image in MeerK40t there’s an option for ZDepth Divide. This will let you split a grey image into several images for different passes. Each with a different banding of the gray. So the darker the gray the more passes it gets. This will actually hit each spot with different amounts of light. And if you’re not just doing on/off stuff you’d want something like this.
It’s pretty easy to see how you’d do this yourself too. You want to hit the deepest cuts with the most passes and slightly fewer passes for the less deep stuff, etc.