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Tricky drone tracking problem – Compositing headlights on to moving vehicle
Hey guys,
LONG time lurker, first time poster.
Like many people, I’ve used CC as an invaluable resource for many years and until now, have always been able to find an answer to any question I’ve had (even if the answer was “it can’t be done!”).
But this current problem I’m having has me a bit stumped.
I have a series of shots of a car driving down a country road, taken by a drone that is chasing behind the car (see link below) and I’m hoping to be able to track some headlight beams and tail light glow onto the vehicle as realistically as possible (we will eventually grade the footage to look as close to night as possible, probably more like twilight due to shadows, etc.).
I’m somewhat familiar with AE’s built in point tracking and 3D camera tracking abilities and have played with these for hours, attempting to get the result I’m after but to no avail. I’ve also tried using Mocha but also haven’t had a great deal of success there either.
I’ve been able to track a small solid onto the car and have that move and scale appropriately but when I try to make “headlight beams” (essentially a cone shaped solid rotated to meet the ground plane), and have them move along in front of the car, they always seem to stray as the shot progresses.
I pretty sure the problem is that in addition to the car moving away from the drone, the camera is also moving forward and sideways, so the perspective shifts too.
TLDR; Is it possible to achieve what I’m attempting in After Effects and if so, what would be the correct way to approach this problem?
Any guidance would be much appreciated!!
Note: Many of the shots in this compilation of rushes will not be used in the final film. The shot at 1:48 is the one I’m currently trying to work on.
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9 Replies
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Vimeo:
“Permission Denied
Sorry, there is no video here.” -
Apologies Kalle and thanks for bringing that to my attention.
I was initially going to embed the video but wasn’t able to.
Fixed privacy settings now.
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This may be a job for Syntheyes or Boujou.
Tudor “Ted” Jelescu
Senior VFX Artist -
Have you tried Mocha on the back of the car?
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I’m snagging the file from Vimeo and will mess with it a little. I’m wondering if 3D camera tracking combined with a pair of spotlights will do the trick.
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Yep, that will do it. Here’s what you do:
Do a 3D camera track. Enter a FOV for your camera–I made the assumption that this was roughly a 24mm lens, and entered 84 degrees as the FOV.
Once you’ve got the camera track, click a bunch of track points on the ground plane, right click, and set the Ground Plan and Origin so that the ground plane being tracked is completely flat. This is key to the next step.
Once you’ve done this, create a grey solid on the ground plane, and make it big–really big, enough to cover the car’s entire path. Set the blending mode to screen.
Now, create a spotlight. Set the spotlight’s Y position just above the ground plane, about as high as the car’s headlight. Set the point of interest waaaay down the road, the direction the car is traveling. You probably need to drop the POI below the plane of the road, so the lights will point down. Adjust the intensity and beam angle to taste.
Go to the first frame where the car enters, and position the light so it matches the headlight position. Now pull the transport ahead a few seconds, and use the X and Z controls to set the position of the headlight–leave Y alone, since the height isn’t changing. Do this for the length of the shot. Then, go back and in-between these keyframes you’ve set, until you’ve basically rotoscoped in the motion of the headlight all the way down the road.
Now, duplicate that light, and either copypaste keyframes with the appropriate X data transform to offset it to the other headlight position, or just do a quick parenting expression with additive math on the X position. Presto, you’ve got your second headlight.
Now you can add secondary lights, parented to these, to create a more complex headlight beam, with a wider, diffuse beam and tighter spot points.
For the taillights, a simple position tracker will do, and you can create some red glow easily, maybe with some very light lens flare to sell it.
10006_headlighttracktest.aep.zip
Here’s the AEP I built using the file I sucked down from your Vimeo; I’m sure you’ll have to re-do all the work on your higher res 1080p file, but you can at least see how it’s set up. Notice that I didn’t go through and in-between all the keyframes for the X and Z positions on the headlights, but I easily could have for better results. Add motion blur, fine-tune the color, add extra copies of the headlights to add complexity…and baby, you’ve got a stew going!
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Oh, and BTW, for some reason the keyframes on the Light 1 position got eased–switch those keyframes back to Linear for a better look.
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Wow Blaise!
Can’t thank you enough for the time and effort you put into your reply! Especially for the super clear instructions and going the extra mile to provide a sample project!
Your solution is similar to my latest strategy (using 3D Camera track to create a ground plane) only much more detailed and comprehensive.
You’ve definitely set me on the right path and I’m confident I will be able to finetune from here to get a good result!
And all within AE, which is always a bonus!!
Thankyou again mate. Really. You’re a legend!
Long live the cow!
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No problem! I was having a slow day, and a little AE experimentation was just the thing to get me through it.
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