I can see that there is a way for PhotogrammetySession to accept object masks. I ensured isObjectMaskingEnabled was set to true, and then I put black-and-white images suffixed with _mask.TIF in the input directory, but they seem to have no effect vs. just not having them at all. I noticed the depth map is rotated 90 degrees, so I tried doing that to the mask, but it didn't make a difference either way.
Example of how I'm formatting it: https://drive.google.com/file/d/1-BZCmncAzHnLEGLTKC2W99tjhTIMvc6Z/view?usp=sharing
I also noticed there are functions within PhotogrammetrySession that allow input of a bounding box. For example, I found this signature under public struct Geometry:
public init(orientedBounds: OrientedBoundingBox, transform: Transform = Transform.identity)
/// Creates an instance with an optional bounding box and transform.
///
/// - Parameters:
///
/// - bounds: An optional bounding box to specify the size of the generated 3D model.
/// If you don’t pass a value, the initializer sets the bounding box to .empty, which tells
/// RealityKit to calculate the object’s size.
But I'm not exactly sure what coordinate space this is using. Is it relative to the pose of the first image or something?