SceneKit SCNParticleEmitter behavior with multiple geometry elements?

I'm working on an ARKit experience that displays a particle effect along detected walls. For performance reasons, I have consolidated all of these effects into one SCNParticleEmitter, and set the emitterShape attribute to a SCNGeometry object with multiple elements representing the surfaces of all the detected walls.

However, the density of emitted particles seems to vary for each of these geometry elements - the smaller surfaces have a higher density of particles compared to the larger surfaces. How can I ensure that the particles spawn over all of the geometry elements with an even density?
You can make the birthRate a function of the surface of your planes.
for example, 10 particles per second per meter square (plane is 1 x 1) should be 20 particles per second if the area of your plane is 2 meter square (2x1).
SceneKit SCNParticleEmitter behavior with multiple geometry elements?
 
 
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