Add dappled lighting to green screen talent?

Ok - I've made some changes:

The particles "fade on/off" over Life — and so this reduces the color choices from 2 to 1.

My recommendation is to adjust Brightness of color for mixing with background. For blend modes like Add, Lighten, etc. to Linear Dodge, adjust color brightness to below 50%. Adjust Opacity as well. I think "subtlety" will go a long way.

I added Random Motion to the "Breeze" effect (parameters set to an "easy" default). (This is separate, so if Breeze is 0, Random Motion can still be applied separately.)

I added a Bump Map. Defaults are Horizontal and Vertical Scale: 0 (horiz) and 0.3 (vert). [Direction and Angle are Options if you prefer.]

There is an option to Show Bump Map Luma so you can adjust the greyscale Levels (visually) for better effect. It is not recommended to *crush* shadows or highlights - go for a relative "even" greyscale.

There is a Refraction Amount that adds a little more distortion to the particles. Gaussian Blur will have an effect on how "obvious" refraction will be.

Same link (different effect name: Dappled Lighting 2B).

https://fcpxtemplates.com/sdm_downloads/dappled-lighting-effect/

The best you can hope for is the *illusion* of being outdoors *under* trees since the lighting is applied on a 2D image from your point of view and not the light shining down from above. This is an Effect, so keep in mind the Effects Masks you have available. Consider masking a face under a hat and lower extremities that are more likely to be shaded. It is also possible to add more than one of these effects to any clip... for whatever reason (and depending on masking requirements).

I also recommend not overdoing it.

Hope this helps!