Now you'll give the project some added pizzazz by creating a gridded background. Creating the grid is easy, thanks to the Grid effect, but making the black area around the Saleen car transparent is tricky. You'll start by creating a new composition to contain the work you've done so far, the grid, and the remaining elements of this project, including the company logo and slogans:
Create a new composition named Master, using the NTSC DV, 720x480 composition preset, with Duration 10;00 seconds.
Drag the Car composition into the Master Timeline starting at time 0;00.
Select the Car layer and apply Effect > Adjust > Hue/Saturation. Turn on the effect's Colorize option (under the Master Lightness property), and set the effect's Colorize Hue property to 0 x +140.0
Go to time 0;00, and create a new comp-size Solid layer named Grid that's any color. (The Grid effect that you'll apply to this layer will override the layer's original color.)
Move the Grid layer to the bottom of the layer stack in the Master Timeline.
Apply Effect > Render > Grid to the Grid layer, and set the effect's properties as follows:
Size From: Width & Height Sliders
Color: Green (RGB: 0, 255, 0)
To fade in the Grid layer, add a 0% Opacity keyframe at time 0;00 and then change the layer's Opacity to 100% at time 0;15.
The underlying grid reveals a black-colored miasma around the car.
Removing the car's black background
The black area that surrounds the car currently covers the underlying areas of the grid and needs to be removed. The first solution that might come to your mind is to use the Color Key effect, which hides all pixels that contain a range of colors that you specify. Unfortunately, the black background contains a wide range of dark hues that also appear within the car; as a result, portions of the car would become transparent, and the grid would appear through the car's frame.
You could use the Inner/Outer Key effect and a new mask drawn around the car to restrict the layer's visibility to the car, but that would require you to animate the mask. That effect provides the best results but requires the most time and patience.
Instead, you'll create a duplicate layer and use blending modes to quickly hide the car's black background:
Open the Car composition, and duplicate the Saleen_Car_07 layer.
Set the Track Matte of the bottommost Saleen_Car_07 layer to Luma Matte "Saleen_Car_07.avi 2".
Add a 100% Opacity keyframe to each Saleen_Car_07 layer at time 6;16, and then change each layer's Opacity to 0% at time 7;15.
If you return to the Master composition, you'll see that the black area isn't visible around the car; however, the grid bleeds through the car in different areas as a result of the Luma Matte. To fix this, you can add solid layers and mask them to fill in the headlights and windshield; these shapes are simple enough that you can then animate the position of each solid layer as needed.