Here are some shots I did for The Secret Life of Walter Mitty. I did the full composite where I had to add a big cloud of smoke from an erupting volcano behind a truck that was driving away from it.
After some time in blocking stage we did a bunch of other tests until the client was happy with the position and timing. From there, it was months of work, integrating everything together and getting more and more detail on the smoke.
I received renders of huge simulations that I had to combine together to form the big cloud. I did the relighting of the clouds in comp. The cloud was separated into 5 different parts and there were around 20 passes in each of the 5 different sections of the cloud. So working with 100 passes for the cloud alone was really slow.
I added CG trees replacing the real ones from the plate. The CG trees were interacting with the smoke cloud. Also I modeled in Nuke some basic geometry of the houses that were on the road. The 3D department took my geometry and used it to create better proxy geometry that the cloud would collide with.
Also I added lots of flying dirt and dust. There were some streamers with rocks coming out the big cloud, these would be hitting the road and the truck.
I also had a couple other shots from the inside of the truck. I added falling rocks and streamers and added the reflection of the big cloud of smoke in the rearview mirror.
Here you can find a clip of the finished volcano sequence.