We are planning a new short movie project that will involve different VFX shots. Thus it was reasonably necessary to test some VFX techniques. The Iron Man VFX Test Shot is my first character animation. I also tested other VFX techniques a lot more, especially 3D Set Extension as well as 3D Tracking and Rotoscoping.
The original footage wasn’t filmed in order to do a VFX shot. It was filmed for a scene from our last private project we developed years ago, while we were still in school. The young woman you’re seeing is a former classmate of us. The shot was never published because we decided to publish a trailer in order to get the project done and thus there was no use for it anymore.
I decided to use this shot for a VFX test because on the one hand the lighting looks interesting to me and on the other hand it seems to be a challenge: How to get a rock solid 3D track considering the reflective ground without much detail? How to credibly extend the underground parking garage catching its lighting? And how to credibly integrate Iron Man in the foreground and let him “interact” with the barrel from the set extension?
First of all I slowed down the speed of the very short clip a bit so I got enough time for the repulsor shot and a few steps from Iron Man towards the camera. After that I tracked the shot searching for tracks of tires in contrast to the reflective ground and adjusted the final 3D Track to match real world size while considering that the young woman’s height is around 5.8 feet and Iron Man’s more than 6 feet in armor. As always I previsualized the shot by using simple geometry and doing a bit posing of Iron Man to get a sense of speed and the general motion.
Modelling & Texturing
In order to enhance the depth of the garage, but also to get the space working on the fluid simulation I decided to do a set extension. First I modelled the rough shape of the garage and then got more and more into the details like the lamps and pillars and of course the barrel.
There are two versions of the 3D garage: One which is completely textured and one that reaches behind the camera and was used for collision detection and to catch the GI of the fire, the direct light of the repulsor and the fire/smoke reflections.
Furthermore, I designed the metal shader for the Iron Man model, but did not texture it (e.g. scratches). This would be the next step.
Dynamics & Simulation
Without any dynamics a VFX shot is half the fun. I did not get into complex rigid body simulations this time, but wanted to improve my fire shader as well as the compositing of the fire to get more realistic results in terms of realistic color gradients.
First of all I set up a particle system in shape of the barrel to skin the barrel later on to the bursting particles. This procedure is much more flexible than prefracturing and simulating the barrel itself. I was able to manipulate physical parameters very fast to get an interesting motion.
Secondly I used a script from Allan McKay and adapted it to my needs with the aim to generate and link simple emitters (for the fluid simulation) to all of the skinning particles. Getting all these simple sources I ended up using maxscript a lot in order to manipulate and animate all the values at once. The technique seems to over-complicate things, but in the end you can sometimes get a more stable and especially faster simulation with simple sources instead of particles.
The final result is what I was looking for, but for a final shot (instead of a test shot) I would have to resimulate to improve the motion of the smoke in terms of an interesting shape.
Furthermore the front sparks that are emitting from the repulsor, get their initial motion also from a fluid simulation and are then transferred to a common physical reacting particle system.
Rendering & Compositing
For the whole undertaking I used the linear workflow and advanced multipass rendering. It’s additional work setting it up correctly, but in some cases I don't need to rerender. This time it was essential with regard to the precise matching of back – and foreground. In this context it was difficult to get a believable transition from CG to the real footage. The fire reflections for example have to be in the CG part as well as on the real plate.
At last, the depth of field (I used the results from rotoscoping to generate the depth map) makes all look more realistic.