Try this in an Expression node in Nuke:
1 - exp(-r)
1 - exp(-g)
1 - exp(-b)
There's a gizmo floating around in the Nuke community that someone showed me quite recently, and it turned out to be the gizmo that I helped Rob Nederhorst to write many years ago. It was nice to see someone showing it me without the person knowing I had anything to do with its creation
I forget what it's called, but the term I used back then was "light space to image space", before "linear workflow" and tone mapping came into the mainstream. This was back when DD had starting work with their RGBE format which of course was later replaced by the superior EXR.
The gizmo basically does the 1 - exp(-x) expression, but has an extra "softness" control, like Terragen's built in soft clip (which it doesn't apply to EXRs). Personally I think this works better than Nuke's SoftClip node, but there more options in Nuke's SoftClip.
In Terragen 3 Professional you can use the "Image File Processor" node to bake Terragen's soft clip and contrast effects into an EXR.
But if you're into the world of film/look LUTs, you probably don't need such simple hacks
Matt
