This was brought up in Bug Reports, but apparently it is not a bug, so perhaps it needs to be mentioned in the Request forum.
Missing Material in both: Material-ID image and Object-ID image
Could the Enscape team please consider giving the option to show transparent objects as solid in the material and object ID channels? For exterior renderings glass is probably the single most important thing to be able to adjust in post processing. The current state of materialID/objectID is useless for this.
A checkbox "transparent as solid and "transparent as clear" would be ideal, or just generate both.
VRay generates solid colors for transparent objects in the ID channels, so it doesn't seem like an unreasonable thing to ask for....?
I guess this was requested previously here a couple years ago: