The Fireworks Sequence

The basic firework was created using the ‘particular’ plugin in after effects.

Then the next step is to place this fireworks on the source footage in such a way that they look as being part of the original footage.For this,the crackers have to be transformed into such a position on the screen,such that they merge seamlessly into the night sky of the source footage.

the transformed fireworks the source footage without the firework

the desaturated footage with the fireworks composited on top of it,the desaturation is to eliminate the color difference the fireworks and the footage.

This is done by placing the fireworks layer on top of the layer containing the source footage,inside the AE project file.

The fireworks layer must be carefully trimmed so that the fireworks begin,only after the camera turns towards the night sky and must stop before the camera turns back towards the actor..if the timing of the fireworks is not perfectly synchronized with the night sky in the soruce footage.it can lead to some really weird effect.And u end up revealing the fact that its a low budget flick ;-) heres how things can go wrong...

After u get the timing and the position synchronized,heres where the fireworks start..

Now once u have the fireworks going off in the right section of the video clip(in the night sky and not on the actors face) u can start to work on completing the other half of the illusion.Inorder to make the viewer believe that the fireworks are actually going off in the night sky and not from inside a computer it is really important that the source footage is motion tracked. Motion tracking is the process of tracing the motion of real world objects in the video clip and then using that data to move the computer generated imagery insync with the movement in the video clip.This basically helps keep the cracker positioned at one spot in the night sky…just like the real ones. We can use the after effect’s built in motion tracker for this purpose.

heres a great link on how to use the after effects built in motion tracker...

http://www.creativemac.com/2003/08_aug/features/stabilizerss1.htm

Now in order to successfully motion track a clip we need to select a tracking point,which is simply a clear bright spot that after effects can keep track of in the video clip.BUT in this case as the night sky is as black as ever.The only way to track the motion of the camera is by ensuring that atleast one bright spot constantly stays within the frame(atleast for the duration for which the fireworks are going to be on screen!) In this case,this point light helps to motion tracking the clip.

u will see that this bright spot constantly stays within the clip for the entire duration of the fire works sequence.And heres the motion tracker in action..

Now once clip has been motiontracked,apply the tracking data from the source footage to the fireworks layer and see the fireworks magically move within the video clip!! As a final,touch tweak the crackers to make them appear as realistic as possible ad adjust their hue and saturation to match that of the video clip.And heres the sreenshot of the final scene...