I’ve mentioned this before, but a truly amazing bit of CGI that I never even thought about was in Forrest Gump.
There’s a scene with Forrest and Lieutenant Dan on the shrimp boat. LD, who lost both legs below the knees in Vietnam, is sitting on the railing, and after talking with Forrest a bit he swings over the railing and jumps into the water.
The problem was, Gary Sinise (LD) isn’t legless. In a few scenes, they had planned to remove his lower legs with CGI, but this one was giving them trouble. They couldn’t film him properly swinging his full-grown legs over the railing without it looking weird.
So they cut out part of the railing, to allow his legs (below the knee) to swing through the hole. Then they added that section of railing back in post-production with CGI. Really cool use of the technology for a split-second of screen time to make his movements look appropriate.
At the time I thought Gollum looked good. Repeat viewings show that he looks bad now, but I think that’s because we’ve seen better. It was really good for its time.
In fact, I even remember thinking he looked good in the first movie, and then seeing the second movie and realizing how bad he actually looked in the first one.
I never found Gollum particularly convincing and was surprised at all the praise everyone was giving him. I’m sure they could make a far more convincing one now though.
As others have said, the best CGI is the CGI I either never notice, or is done so well that I can’t tell the difference.
Bad CGI is usually just done badly; A recent movie I watched (I don’t recall which)had an obviously CGId helicopter flying over a cityscape. The lighting, reflections, proportions, and its clarity against a the slightly-out-of-focus cityscape just shouted CGI.
The effects in Heavenly Creatures (which happens to my favorite movie of all time) are an integral and necessary part of the movie, not shiny crap stuffed in just because they could.