The completed project file for this tutorial and sample clip can be downloaded in Hap Alpha 1080p.
While VDMX itself is an application for creating real-time visuals, eventually most VJs and other visual artists have some use for other types of video software on the Mac such as non-linear editors (iMovie, FCP, Premiere) or motion graphics generators (Motion, After Effects) to create pre-made footage to mix during live performance.
When exporting movies from other software, often it is an option to include the transparency information known as an alpha channel for each pixel that can be used by VDMX to automatically adjust the opacity of different parts of the image during real-time composition of layers. This is particularly useful when you want to create the appearance that one layer is "in front of" other layers behind it, instead of simply blending the two layers together as when using the 'Over', 'Atop' and 'Mix' style composition modes that use alpha channels in this manner.
Most of the standardly available video codecs on OS X do not support alpha channels- when including transparency with QuickTime movies typically 'Hap Alpha' and 'Apple Animation' are the two best choices for use with VDMX. The 'Hap Alpha' codec features a substantially lower data-rate and CPU load than 'Apple Animation', but the image quality isn't as good. See our blog post on the Hap codec family for side-by-side performance comparisons of the two.
In this tutorial we look at exporting movies from Apple Motion to use in VDMX and including the alpha channel by using the 'Hap Alpha' codec. The same basic idea can be used with other motion graphics software such as Adobe After Effects.
1. Export the Motion project as a high quality QuickTime movie and then convert it to Hap Alpha.
In some software, such as Apple Motion, only certain codec options are available as export options. In this situation it is best to first render to a high quality or lossless format that includes an alpha channel, such as Apple ProRes 4444. Once exported as a QuickTime movie, open the file in QuickTime Player 7 or the free Vidvox Batch Exporter utility to transcode it into the 'Hap Alpha' format.
2. In VDMX use the OpenGL Over blend mode, or the GLSL / Mix composition modes.
By default, new layers in VDMX using the OpenGL Additive blend mode which is useful when working with movie files that don't provide alpha channels. However, to have the "foreground" layer (the one on top) appear "in front of" the content behind (below) it, a different set of blend modes are available to create this effect.
To get the best performance when using movies with alpha channels, layers should be set to the OpenGL Over blend mode, or the GLSL / Mix composition mode. If using CoreImage, the VVSource-Atop mode can be used instead, but it may be slower.