Compositing Translucent Glass with After Effects Plugins
Adobe After Effects Plugins can be used to capture semi-transparent objects, including translucent glass. This effect can be done via both the BCC Chroma Key Filter, which allows users to capture foreground images and move them onto to different backgrounds, and the Spill Ratio slider. This effect can be done by using a green screen, video camera and After Effects.
Step 1: Understanding BCC Chroma Key
The BCC Chroma Key Filter is one of the best ways to capture nearly transparent objects, including glass. The filter can differentiate between objects in the foreground and background by finding the saturation of the background object and removing it.
While green screening has been done for ages, the BCC Chroma Key Filter is a bit more advanced because it can find the finer details in the shot, including shadows, and carry those over to the new background.
Step 2: Using the Green Screen
The first thing that any user needs to do is pick the correct matte (non-reflective green screen) color. Generally, they come in blue, green and orange, and they should be a solid color. The trick is to find a screen that contrasts with the foreground color, but still has some of the shades of the new background.
Step 3: Using the Chroma Key Filter to Composite Images
Once the background is set up, put the semi-transparent glass in front of the background. Then, pull up the shot in Adobe After Effects, and open up the BCC Chroma Key Filter from the BORIS RED or BORIS FX plugins. This tool can usually be found by going into Filters and the Keys. Now, go into the Mattes panel.
Step 3: Changing the Background Color
The blue is the preset in Color section of the BCC Chroma Key, but this color should be changed to actually match the screen color. To change the color, select the eyedropper tool, and take a sample of the actual background color, which can be done by picking an area close to the actual subject, the translucent glass. Because there are shadows and color variations near the subject, it is usually the hardest to match.
Now, let the Chroma Keying Filter do its work. It will automatically search for the most dominate shade in the background and then remove all shades of that color from the background. This will effectively remove the entire background, but leave the foreground image. The entire background should be removed the first time around. If it is not, then simply use the eraser tool to remove the rest.
Step 4: Restoring the Shadows
Sometimes, the shadows that were present in the original get lost during the compositing. But, they can be added back into the new image by using Spill Ratio slider. Slide the Spill Ratio slider to around 40, and the shadows should reappear.
Step 5: Putting the Image on the New Background
Finally, just place the new background behind the foreground image. Look for any lingering traces of the matte, and remove them if they are still present.