How to transform box mask to world space?

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I am working on a vr portal system which draws a series of boxes outlining the field of view through a “portal window.” The trouble is I have had trouble getting the box mask to do what I want. I am passing it the extent and center of the boxes which I want “cut out” of the object however I cant figure out how to transform those positions and rotation into the world space. Any help would be appreciated.