As the resident Terragen PR geek I am reasonably informed about such things.
The "TGD" rendering engine core was basically in early development during Star Trek Nemesis. Matt was working at Digital Domain at the time. I believe it was used for texturing on some planetary shots, but it was not - as far as I know - heavily relied on. There were a number of planet shots, including the end shot (orbit above Italy I think) that did not use it, and I don't believe it was used for any on-planet shots, much as I hoped it would be at the time.
The first real showcase for this technology was Stealth, where it was used on literally hundreds of shots. Keep in mind however that Matt had left Digital Domain by this time. DD retained the right to further develop Matt's original "TGD" technology and that became DD's own "Engen" product (often still referred to as "Terragen" because of the history).
Engen was developed based on Matt's "TGD" code, but it has gone in a somewhat different direction, tailored to DD's specific needs in its pipeline. For example all the trees in Stealth were done using Houdini rather than instancing and object rendering technology in Engen. I'm not sure if Engen has such capability, but given the fact that they have strong tools that already handle this kind of thing, I think it's unlikely that Engen has robust object rendering. Likewise because of DD's own "Voxelbitch" (Storm) volumetrics renderer it's probable that Engen doesn't have its own volumetric cloud system like TG2 does. Still the core landscape rendering technology is fairly similar and the results are of course excellent.
In Stealth much of the terrain was given heavy motion blur so although it did look very good, it didn't have to look truly photoreal in most cases. The motion blur removed a lot of the small cues that would give it away. However in Flags of Our Fathers they ended up using Engen for a lot of largely still "locked off" shots as backgrounds. These naturally had to be even more convincing, and from what I saw in the theater myself they were. I actually had a tough time distinguishing the Engen shots from the rest, although of course the rest of DD's process (compositing other elements and color grading) contributes to this greatly.
Frankly it's remarkable we get the realism we do out of "stock" TG2. It's when you try to combine this with real-world elements (photo) that you see the differences and matching it up is really hard. That's what effects companies like Digital Domain do. Very cool work.
- Oshyan
