Quote - My suggestion for those interested a linear workflow is to use OpenEXR where ever possible. That format is specified to be linear and most software seems to respect that.

Unfortunately, the Photoshop support for OpenEXR is very basic and it doesn't show extra outputs. There are 3rd party plugins like ProEXR.

To come up with an ObjectID from a color, it's red * 65536 + green * 256 + blue, assuming that your colors are in the 0-255 range. Yes, it is quite similar to the way colors in the UI XML are specified.

AHA!! Thanks for that!!