The previous math forms are the only truly accurate description of each blending operation, but short descriptions are below where Source is the output from the next track and Destination is the output from the lower track stacking. Blending starts with new Source and combines it with the previous render stack output, which is referred to as Destination. The new output becomes the next Destination and the next up stack level becomes the new Source. Source is above; Destination is below.

Some notable items that affect the results are listed here.

  1. So as not to be surprised by the results, set your Video Driver to X11, not X11-OpenGL, because when rendering your video no graphics library is used. Rendering is handled in software and there is sometimes anomaly differences when using the OpenGL driver.
  2. The Graphic Art group operates principally on color, and the others operate principally on alpha.
  3. When using the Title plugin with text, blending or changes in the text will only take affect in Subtract, Divide, and Difference. This matches the implmentation of the original Cinelerra version.
  4. If comparing results with the original Cinelerra version for Subtract and Divide, you may have to switch the order of the source and destination tracks to see the same output. If you do not want to switch tracks, you can use the overlay plugin as shared and change the Layer order and/or Output layer. The reason for having to switch tracks to get equivalent output is because of differences in the math formulas used. Subtract exactly matches the original Cinelerra version if you switch the 2 tracks; Divide matches in one order only.
  5. Instead of using the patchbay overlays, you may prefer to use the overlay plugin instead.
  6. If you see undesirable results, always check under Settings->Format and check your Color Model as that will vary or interfere with the look.

The CINELERRA-GG Community, 2021