Hit by a Car - FX Demo: How To
Anyone who's seen my video work can pretty much tell that I love playing with special FX (effects). I experiment with them, use them in my productions, and also find myself being asked how to make them by other visual effects enthusiasts.
After seeing the FX demo to the right, Niels wrote to me asking:
"I have to get the "get hit by car" effect, but i dont know how to film this... Can you please help me, just give me a short explanation? I really need your help!"
I'd be happy to help, Niels. :-)
Achieving an effect such as this isn't very difficult, but it does require some planning and time spent in postproduction for it to turn out properly.
The live action for this sequence was done in two separate shots/takes: One shot of me running out and picking up a dollar on the ground, and another shot of Ron Shuboney (stunt driver, extraordinaire) speeding past the same exact location.
Setting up for the shots involved careful placement of the video camera on a secure tripod mount. The shot had to be aligned carefully so that both elements (human subject and car) would appear in the picture properly. The path of the car also had to be precisely determined and marked prior to driving by. Failure to do so may have resulted in the car not lining up exactly with my position when the two shots were blended together in postproduction.
Proper and consistent lighting is very important for composite sequences to work well. This can be difficult when shooting outdoors because you're literally at the mercy of nature. It may seem all nice, sunny and consistent to the human eye, but even minute differences in lighting will stand out like a sore thumb when the shots are combined. The trick is to shoot both sequences with as little time between them as possible. This helps minimize small changes in lighting and the movement of shadows.
Once both elements are shot, the video needs to be captured on your computer/video editor. There are dozens of ways to achieve this effect and I'm not sure that my approach was the best way, but this is how I did it:
The footage was reviewed and the action portions of each were charted out. Each video element was exported as individual frames (BMP files). Here's where it gets time consuming: To achieve the best possible blending of two video layers for an action sequence like this, I do it one frame at a time. In this case, I copied an area around myself in each frame of the me footage, and blended it on to the car footage frame by frame in a photo editing application. For the impact, I manipulated my shape slightly to simulate impact movement, and add some horizontal blur to simulate motion blur. Since this was just a demo shot and I didn't want to spend a lot of time on it, I went with a simple impact sequence where I was basically pushed off frame by the speeding car. The physics of an impact just pushing someone along like that is somewhat unlikely, but the shock value is still pretty good as most people have never actually seen a person get hit by a car and therefore do not know how it looks in reality. It is possible to make an effect such as this as realistic as desired - one is limited only by their tools, resourcefulness, and time they choose to spend on it. In Hollywood it is their business to thrill audiences and be as realistic as possible so they put a lot of money and manpower in to each visual effects shot for their big budget productions.
Shadows had to be retouched as well as some background imagery to make the shots blend together properly.
Once the frames have been blended together, they need to be re-imported in to the video editor as an animation. Drop the animation on the time line, add sound effects as desired and enjoy the thrilling video footage of a pretty convincing high-speed human/car impact!
As with most visual FX shots, this one is not perfect. Aside from the already mentioned funky physics of the impact, there are some errors present in the video compositing. Since this was just a demo shot and I didn't want to spend too much time on it, I smoothed out things a bit, and left some noticeable image glitches in there. Most people don't notice them. Do you? If not, than remember that your visual effects need not be perfect either. Although the imperfections in each shot may stand out to the author of the effects, the audience will likely not pick up on it. ;-) The same goes for Hollywood. In ALL major motion pictures, there are dozens, even hundreds of errors from continuity to visual effects glitches. The secret is to draw the audience in to your story (or just in to the moment) and they will probably not notice each little imperfection.
- The the tire-squealing sound effect in the video was the actual audio captured of Ron's car speeding past while on a tight turn. The only sound effect added in post was the impact.
- This demo clip was used as a sight gag in one of my QuickVids. Check the video to the right to see it.
- The atomic weight of titanium is 47.867 Amu.
Did you find this article interesting, helpful and insightful? If you enjoyed reading it, please let me know. Shoot me an e-mail or use comment feature below. I'd love to hear from you. :-)