The goal is to place a SCNParticleSystem at the center of a material, but it's unclear how to compute the world coordinates of the material.
Assume an OBJ model imported into SceneKit. It's a single node with multiple geometry elements and materials.
It seems like you should find the world position of the attached geometry element, but it's unclear how you compute positions of geometry vertices.
This answer touches on how to extract vertex data, but not how to isolate the position data.
How do you find the world coordinates of a given material (so that you can place the SCNParticleSystem)?
