The objective of this tool is to generate object mattes from a 3D render using the RenderID and the coverage passes..
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RenderID pass must be embedded in the EXRs for this tool to be utilized.
Coverage pass is needed for the anti-alias treatment.
img.1
Move the position pointer around to select the mattes.
img.2
Turning Selection Overlay ON will enable you to see the object being selected (as shown in img.2). Turning this setting on wont show the artist what has been added to the matte, only the matte that is currently selected. The matte is added only when the artist presses Add Matte button.
Added mattes will be in the alpha channel; RGB will stay as is.
Add Matte: Adds the selected matte to the output.
Remove Matte: Removes the selected matte from the output.
Clear All: Removes all mattes.
Additive Alpha: Preserves the incoming alpha channel so that the idSelector nodes can be stacked.
> Reset range when new ID is picked: Resets the range back to 0 when a new color ID is picked. Keep this turned on for most scenarios.
> Use Multiple IDPickers: Uses multiple IDSelection nodes to select the given range instead of using just one IDSelection node with a zSlice range.
Advantages of multiple picking is you can remove individual IDs within the range as opposed to not being able to edit the selected range.The disadvantage is that its slower especially when selecting a wider range.
WORKFLOW TIP: While looking through the idSelector node, turn on your mattes (Shortcut: 'M') to see the current selection of mattes.(as shown in img.3 below)

img.3
Short video of how to use this tool can be found here.
https://youtu.be/2mXo6e8QO7Y?t=3m44s
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