Placing an image of a car into a video

B

_bli

Active member
So I'm asking anyone who can help to help me out on how to place an image of a car into a video. The scene is the main character wlaking down a sidewalk passing some parked cars. A specific car seems to be parked next to him every time.

I don't have access to the real car so I want to put it in "virtually".

Would this be the right procedure as to achieve what I'm trying to do?

1) Film/take a picture a model car in front of a green screen in the correct lighting/correct angle.

2) Track the street area where I want the car to be in Mocha.

3) Bring the data over to After Effects at which point I will bring the model car picture into my main video, chromakey the green out, add the data from Mocha to this specific layer, scale it down & position it correctly in the street.

Would this be right?

If it is, I have one more question. How would I go about having the car behind certain things, like a person passing in the foreground or a tree? I'm going to assume mask out the person or anything in the foreground? But that's as far as my skills allow because I'm unsure as to how to proceed after that.
 
Sounds about right- alternatively you could use a 3D car if you're comfortable with rendering. This would skip the keying process because you can render mattes from any 3D program- but you'll still need to track your shots.

Also- your greenscreen lighting (color, specularity on windows & chrome) will need to match your real scenes as much as possible(or be easily faked). Unless the model is really stunning, or far away in the shot, it might be obvious it's only a toy car. I would do some quick and dirty tests and just throw your car in a shot and see if it even halfway looks right before going too far down the comping road.

If the fake car is behind real elements, it's good ole fashioned roto time.

Are you sure none of your friends have this actual car? :]
I'd ask around.
 
You don't mention the angel you're planning to shoot the car/walker? I wonder about those, and how many different angles?

Just imagine, if you could get that car or another one that would work as well...then voila: No AE, just shoot! Ahhh! No offense to you. I love AE! But...I'd always rather get what I can get straight into the camera!
 
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[TD="align: left"]First off, let me simply point out that there's several ways to approach this type of shot. In theory, most of what your saying would definitely work, however, if you want your shot not to look too unrealistic than I might suggest a few things.

1.) In regards to the model car, I hope you mean "model car" as in 3D and not as in a "toy car". I don't know how realistic that would look, IMO.
In that case, there's no need for keying a picture/footage of the car.

With that said, the lighting needs to be spot on (especially when it comes to the reflections in the windows / windshield and of course the paint of the car, as well as the detail in your shadows).

I would suggest using a HDR image (that matches your footage) to light your scene when you import your footage into 3D. Not sure if you have worked with HDRI before, however, this is the only way your car will be lit correctly and properly coexist within the same shot.

2.) When it comes to tracking, I think there are far easier ways than using Mocha to maintain an accurate enough track. The task might become more tedious or time consuming otherwise. You should take a look at The Foundry's Camera Tracker (http://www.thefoundry.co.uk/products/cameratracker/). It's a very intuitive and cost effective match moving plugin. If you plan to continually track shots such as this one, it will pay for itself.
This is of course only one possible option but it gives you the flexibility of staying within AE to track any of your shots. Also, it might be useful to point out that this would be the first step in the process. I would then send all of my data to 3D.

3.) When everything is all set in 3D, I would export the car with an alpha channel (and your background footage shut off). Quite simply, everything should render a bit faster this way. You can then composite your car into your scene in AE and it shouldn't be too difficult to "set it in" since most of the work would already be completed in 3D at this point.

4.) As far as having elements exist in the car's foreground, such as a person passing in front, I would green screen the actor (as you said with the correct lighting/angle) rather than masking them out. Because there is movement involved, this will avoid having to manually mask things out frame by frame. Don't forget to account for shadows and reflections that would be created as well. For objects such as trees (or objects where there is no movement), I would mask those particular elements out (or key them) due to the fact that you can get away with masking just a single frame of a tree for example.

Again, there are plenty of ways to approach this, although, this would probably be the way I would handle this specific shot. Hopefully I didn't lose you or cause any confusion. This is one of those circumstances in which the level of difficulty is totally dependent on how well your shots are planned. Above all, I would plan how you will execute your shots for post before tackling this endeavor. Good luck.

-B

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