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Mixing lighting data

With Beam, lighting data follows the same signal flow as audio. That includes the concept of mixing lighting data from several tracks or chains.

For audio, the only way signals are mixed is by adding them. For lighting data, this is different. To disambiguate between audio and lighting data, instead of mixing, we speak of merging.

In general, we have taken care to make sure merging gives you the results you would expect. But if you want to know the fine details, read on.

Merging tag groups​

Only parameters that have the same tag group are ever merged. The parameters of different tag groups live side by side in a signal chain and never influence each other.

If track 1 has an instrument set to group Strobes, and the instrument on track 2 is set to Beams, whatever happens in track 2 is unrelated to what comes out of track 1. But as soon as the group of the instrument in track 2 is set to Strobes too, the dim values of track 1 will now be added to dim values of track 2.

Merge modes​

How we want to combine values from tracks strongly depends on the type of value. The exact way in which the parameters coming from multiple tracks are dealt with can be different per parameter type and per fixture type.

The merge behavior is specified separately for every parameter in the fixture profiles. Below is an explaination of the available merge modes.

Add​

Parameters of all tracks are added. This merge mode is most useful for parameters like dim and iris, where you simply want a higher value if multiple tracks are using it.

Weighted Average​

Parameters from all tracks are added and divided by the amount of tracks. This is most suitable for color and position parameters. Instead of all parameters eventually ending up at their maximum values, e.g. fully left or fully white, the result will be a combination of the individual tracks. For example for panning, the resulting rotation will be in the center of the individual tracks' values.

Before averaging, the values are multiplied, weighted, by the track or chain volume. This means that the influence of tracks or chain with a lower volume will be less than with a higher volume.

For Drum racks, the numbers are additionally weighted with dim (see the Dim scaling).

HTP (Highest Takes Precedence)​

Parameters of the two tracks are compared and only the highest is used. This is most useful for slot-like attributes such as Color wheels and Gobos, where interpolated merging would not result in useful values, at least not for common usage.

Note that the parameters of tracks and chains are scaled with the track or chain volumes only when determining which one is higher. The values themselves are not scaled with volume.

Parameters in racks​

The signal flow in racks works exactly the same as between tracks: the outputs of the chains are merged according to the merge setting of the fixture parameters.

Drum racks, though, have a special extra: notes can control not just the dim, but all the parameters. This is implemented by making weighted averaging use dim scaling.

Dim scaling​

In Drum racks, for parameters where the fixture profile specifies weighted averaging as merge mode, after the track or chain volumes, we also multiply the numbers with dim before averaging.

This effectively makes the parameter's influence follow the momentary intensity, which is in turn controlled by the Attack-Release envelope, which is triggered by MIDI notes. In short, in Drum racks the note envelopes control most other parameters.

In Drum racks you may be merging between up to 16 different parameter configurations for the same group of fixtures. When triggering the dim with envelopes, as you typically do in Drum racks, the result of dim scaling for weighted averaged parameters like pan and tilt is that the most recently triggered Drum rack slot shows up most prominently in the merge result.