Videos with alpha transparency

Usually and on many sources online it is common to share special effects (VFX) used to enrich videos with a colored background. Often times green or blue. Then the artists has to use a chroma key filter to then extract said background color and make it transparent. But this does not need to be the case as we can create special effect video files with a baked in alpha channel.

For this we can make use of Blender.

• Setup your effect in Blender
• Navigate to Film
• Check transparent
• Render your animation into PNG or webp files with alpha channel enabled.

After this has been done then open a new Blender file New -> Video editing

• Import your previously rendered animation as an image sequence

• Navigate to Output
• Choose FFmpeg Video
• Select QuickTime as Container
• Set Video Codec to QuickTime Animation
• A new button will appear below FFmepg Video at Color
• Set RGBA
• Export the video

Tada alpha channel VFX.

Here is a comparission between the color keyed VFX (right) and the alpha channel one (left). As we can see sometimes there will be get a colored shim around the effect. In this case green because the background of the VFX was green.

Also using color key based approach will force artists to keep any eye out on colors used for the VFX as the chroma key filters do not know which part of an image is the VFX and which part is not. Or to work with masks and the likes. Green is Green. Also we save a ton of time setting up a chroma key filter in the first place. Simply put the VFX onto the footage and that's it.

Source