I didn't have high hopes for this film, as Starship Troopers is the type of franchise where, like Aliens or Terminator, you really need a big budget to properly do justice to on screen. And seeing as this clearly wasn't a major production on the same level as FF: The Spirits Within, GitS (1995), or even FF7: Advent Children, I was expecting it to be on the same level as Appleseed or Renaissance or, at best, Ultramarines. I mean, just look at what happened with ST2 and ST3 with their $9M budgets (about the same budget as Ultramarines).
However, I was actually pleasantly surprised by the animation quality of this film. It's not The Spirits Within, but it's at least on par with Advent Children. The film doesn't go for an ultra photo-realistic look, but the bugs, the armor, the ships, the environment, etc. are all exceedingly well rendered. The bugs in particular look extremely realistic (especially being chopped down by machinegun rounds), as do all the on-screen physics.
Still, there _were_ some flaws... First off, there's a distinct anime aesthetic to the film that seems ill-suited for this franchise. You'll recognize the costumes, equipment, etc. as being from the ST universe, but still with an anime-spin to it. This is especially obvious in Carmen's weird Gundam-style sci-fi-Victorian uniform. Somehow, a baby blue "crop top" military dress jacket and matching corset just doesn't seem to fit the ultra-macho, utilitarian culture of the fascist Terran Federation (nor the rest of the ST universe). In fact, she looked more like a flight attendant than a starship captain.
Likewise, the body and facial styles in the film are all stereotypical of anime characters--to the point that most of the male protagonists look pretty much alike. I suppose that's why they had to resort to giving Rico an eye patch, Hero a distinctive scar under his eye, and Holyman his weird anime-style tattoos and pale complexion.
Even the semi-mechanized mobile infantry body armor/spacesuits seemed to have a bit of a corseted waistline. That said, the ships, armor, and space station designs in this film are still very high quality overall, rivaling even the first movie in some respects. Even the overly-Halo-inspired-corset-wearing MI battle suits are better looking than the armor shown in any of the previous ST works. Though I personally would have stuck with the black and field grey color scheme for the mobile infantry gear/costumes instead of the jungle green cameo (this is supposed to read C-A-M-O, as in camouflage; please ignore IMDb's idiotic autocorrection) they used in the film, which is more reminiscent of U.S. marines than German storm troopers (and also not making much sense in space or inside of the silvery monolithic starships and space stations).
The overall CGI quality is actually very impressive considering that in theory, Stage 6's target production budget is at most the same as that of Ultramarines (the admirable but ultimately disappointing WH40K animated film), and yet ST: Invasion is head and shoulders above what Ultramarines managed to achieve with their budget.
If you want to be picky, sure, there are a few stereotypical mannequin moments that nearly all 3D animes tend to have, where the body movements seem a bit too rigid or the facial animation doesn't seem quite right (like the virtual actor had too much Botox). But all of this is fairly easy to overlook when you're fully engaged in the plot and action.
Alas, there is ONE critical area where ST:I falls flat on its face: voice acting. Carmen and Johnny's VO actors were decent, but much of the rest of the cast did not seem to be voiced by professional voice actors (or at least properly cast voice actors)--another sign of the film's anime heritage--and was quite painful to sit through. Like so many other great Japanese animated works, this one was ruined in the final leg of the race by a studio that just didn't care enough about the English voice-overs to get it done right.
It's a real pity, as the story was actually pretty serviceable and the rest of the film was very high quality overall, with only the aforementioned quibbles (all fairly minor and easily overlooked), and would probably do well with a major release in North America if not for the painfully bad English VOs. And supposedly this film was never even dubbed in Japanese (at least Akira and most other animes with poor English dubs are watchable in Japanese with English subs). It's such a severe flaw and stands in such stark contrast with the rest of the film, that I'd consider petitioning Stage 6/Sony to release the raw audio tracks of the film and let the community re-dub the VOs.
