I (ed: Richard Levene) am Director of Creative/Technical Operations at Recom Farmhouse (http://www.recomfarmhouse.com) where I have been working for almost 4 years. Many of our jobs have been for car clients and I have produced many car renders over the years. Guess this is why my friend Marijn (vfx sup.) thought of me when it came to thinking who could do the car for this shot
Shot task overview
I was tasked with animating, bit of modelling, shading, lighting and rendering the car for this shot. Have to admit that animation is not something I have done a lot of. At work we tend to produce still images and we have done very few animations, the odd car turntable but never a moving car. Thankfully the car was only required to move in one direction so I knew it would not be too tricky, but I was concerned with how easily/quickly I could animate/keyframe the fine details of the car like tyres reacting to the terrain and the subtle car body movement that add to believability.
Starting the shot
First thing I did was import the matchmoved data into a new Maya scene (Maya 2011 x64 Subscription Advantage Pack) to make sure there were no problems. I always work in ‘cm’ units so had to make sure the track was coming in at the right scale. The tracking units were in meters so I grouped the camera and ground plane geometry provided by Marco and scaled it by 100 units. I applied the image sequence of the plate to the imageplane and everything lined up perfectly. Then imported the model of the car to check the scaling of the car to the plate looked correct. Which it did.
Animating the car
The release of Subscription Advantage Pack for Maya 2011 meant I was able to try out a new plugin shipped with the update. Craft Director Studio. I had seen a video demonstration of the plugin on the Autodesk Youtube channel (http://www.youtube.com/watch?v=0KqLe66uFG8) at the point of the release and thought that this would be the perfect opportunity to test it out and it could be the solution to my animation fears.
The plugin comes with a few free pre rigged vehicles that you can control and parent your models too. You are then able to control your car and drive it around using your keyboard or joystick/pad directly in your Maya scene! You have controls to adjust the suspension and weight of the car, as well as the it’s acceleration, top speed, maximum steering angle and braking force. Check out the link above for a look at it in action (skip to time 1:04).
The model of the car I had was very dense so in order to get good real time feedback while controlling the car, I created a very rough proxy version and parented that to the dummy rigged vehicle instead. The parenting requires you to have your model grouped in the same way the plugins rigged vehicle comes. Groups for each wheel and body.
The best part of this plugin is that your vehicle will respect the ground plane. So if you have a very bumpy ground the car will react to it and follow the geometry.
So I subdivided my ground plane geometry quite a bit and used the Sculpt geometry tool to pull and push bumps into the road to mimic the bumpy desert ground. Very very quick and roughly.
I was now ready to record my car animation. I only had to drive the car forward in one direction so not much work or control was needed. After the first playback I could see the ground was too bumpy and it needed to be toned down. I adjusted that and was happy with the result, so I baked out the simulation to keyframes. With this I was then able to manipulate the animation curves to control the speed of the car and positioning to meet the directors in and out points.
I then parented my full res car geometry into the vehicle rig groups and I had my full res car animated Here is the approved playblast:
With this animation signed off, I sent over both the proxy and the full res geometry car animation scene to Erik for him to use for the cloud simulation and dust interaction renders.
Shading and lighting
Prior to starting on this shot, I had just completed a job using Vray on a project at work. I was very new to the renderer and thought this would be another good opportunity to learn it even more. I have always been a mental ray user but for the particular job at work, we needed the ability to interactively light our car with geometry mesh lights and the custom geometry light shaders that are available for mental ray do not play nicely with IPR. Vray RT and geometry mesh lights proved to be a winning combination. The Vray plugin for maya is very well integrated and it is very easy to use compared to mental ray in Maya. (Will leave this for another blog post)
With the car being black, you can only really light such a car with reflections so the hdr was very important for this. The hdr was supplied to me by Marijn, taken from on set while filming. It was not from the same location as the backplate sequence, but it was in the desert, so you would never know. However the time of day the hdr was shot at was slightly different, also the colour balance of the hdr compared to the plate was drastically different.
In order for the car to sit nicely in the plate some Photoshoping was necessary to get the hdr to match the backplate better. I very crudely replaced the sky and made the sun a lot higher as well as grading the ground.
I had reference images of the real car on set so was able to get a better idea of how it needed to look. I started to apply some shaders the main shaders such as the car paint, glass, black plastic, rubber, chrome etc as well as creating a tyre shader and texture to make it look like the tyres had been driving in the sand. Some quick UVing of the tyres was necessary for this.
Here is an early test with low sampling.
A few tweaks and I was ready to setup up for final rendering.
We had worked out in previs that the car would become visible through the dust cloud at around frame 35, however to be safe I setup the renders to start from frame 25.
I split up the car into 3 elements. The car body, wheels and shadow. The reason for separating the wheels from the car was due to motion blur. We knew we would want the car motioned blurred but I was unsure at how long it would take to render both the car and the wheels motioned blurred in the same scene. We worked out we could get away with motion blurring the car body in post using a motion vector pass (velocity pass) from Vray but the wheels would need true 3d motion blur. So splitting them up was the best option.
Various render elements were created along with the beauty to give Linus more control in comp, but I think as we had such little time he only really used the beauty pass of the car body and wheels. Lots of masks were rendered as well for all the various materials.
I was really happy with the quality of the car. Looking back there are a few things I would change regarding the car. I would add more motion blur to the wheels. Unfortunately there was not much time for rendering so I kept the motion blur quite minimal to assure all passes were rendered in time. I would also tweak the car animation slightly. Near the end of the shot the car body jutters quite a bit (only a few frames) but this would not really happen on a car like this. The suspension would smooth it out. But think I am just nit picking
Overall I think the final shot looks amazing. I thought it was going to be really hard to marry all the effects together, but Erik and Linus did an incredible job. Not only was this shot great, but every shot that was completed for this project looked brilliant. Huge credit to everyone that worked on this project and it was a pleasure working with everyone.