Actually, there is no need for that. Edge blending with rotated projectors works exactly the same as with normal edge blending. This is because in Resolume the edge blending is set up in the Input Selection, which is separate from the actual output to your projectors.
For this I'll assume you're using a Matrox Trips with 3 projectors set to 1024x768. It will work with discrete outputs as well.
Make a comp of 2560x1024. That covers the width of your 3 projectors (768+1024+768) and the maximum height of them (1024, because they're in portrait). You'll lose some of the width because of the edge blending, but it's a good starting point for the setup.
Create 3 input slices, the middle is just 1024x768, dead in the center. The left and right should be 768x1024 (to take into account the portrait mode), and moved in towards the center to duplicate your physical projector setup. For more info on this aligning, check our edge blend tutorial. The principle is exactly the same, only your left and right slices are in portrait.
Then in your output, set the middle slice to be 1024x768, dead in the center again. Left and right should be 768x1024 again, but rotated 90 degrees clockwise or counterclockwise, depending on how your projectors are rotated. Position them to the left and right of the center, so you exactly fill your 3072x768 TripleHead output.
Turn on edge blend, and fix any alignment errors, and you should be good to go.
