With this node you can make a precomp in just 1 click. With the exr/mxi read node selected, press the button 'AUTOCOMP'. The script separates each light in a MXI node, it ticks solo and renames the node. Finally, it merges the node with the rest of the lights and create a Master node to control yout lights. You can also load an emixer file, create a backdrop node and shuffle and premult the alpha.
MXIAutoComp
Updated: 8 May 2015
Author: Anquiro
Compatible Nuke versions: 7.0 or later
Compatibility: Linux, Mac, Windows
MXIAutoComp is a compositing node for Nuke that mimics the capabilities of Multilight in Nuke from EXR render footage. The node allows you to extract the light buffers embedded on an EXR image file or sequence (if rendered with Multilight enabled) and automatically creates the complete nodes compositing structure associated to the lights embedded and mixes them adding independent intensity controls to each light, providing you the same adjustment capabilities as Multilight sliders do (but enjoying the noteworthy savings in file size derived from using EXR instead of MXI files). It also allows you to extract the extra render buffers embedded on the EXR render and even import the emitters sliders configuration from an external emixer file.
Maxwell Render Tool
V.2.0 (Update):
-Unlimited Lights
-Better performance
-Master and aligment in the same click of the Auto Comp.
Look at the video for more info: