Using Midi Fader Controller to change Geometry.

[Paul Simoncelli]

Hi Folks, is there a possibility to use a midi fader controller to change e.g. translation, rotation or scale. I tried, but couldn't find a solution. Thanks in advance.

[micpool]

Yes, but it's not straightforward

You can use OSCULATOR, Chataigne, Max, or a similar program to translate MIDI to OSC or use the cue list look up table  method detailed here.

https://qlab.app/cookbook/mind-bending-midi-binding/

The challenge you'll face is scaling. If you map the 128 values of a MIDI fader to an x translation of -1000 to +1000 for a  small object to traverse a 1920 x 1080 stage, then each change of MIDI cc value will move the object 14 pixels e.g MIDI cc 0-127 to /cue/1/translation/x {number} where number is a value from -1000 to 1000 pixels

Scale 0.1 to 10 is also quite steppy.

Rotation is more problematic as you need to target a fade cue to your video or text cue, set an x, y, or z fade, and ensure the live preview is on. Again, with a translation to -180 to 180, each midi increment will rotate 3 degrees. If you target the cue itself and translate the MIDI to /cue/1/rotate/z then you will add the value 0 to 127 to the current z quaternion rotation. This means the rotation will only go in 1 direction, and the steps will get bigger or smaller as the MIDI value changes.

If you want to use a rotary control then a continuous encoder (not MIDI)   that sends a keystroke for +1 and a different keystroke for -1 for each click. like a Contour Shuttle is more useful as you can then trigger 2 OSC cues to send /cue/1/translation/x/- 1 and /cue/1/ translation/x/+ 1, which will add or subtract 1 pixel from the current x position of cue 1. However, you will then have a problem with gearing as you will need to turn the knob 2000 clicks to get from 1 side of the screen to the other, which will be about 20 turns of an encoder with a 100 clicks per turn resolution.

So what you really need is an encoder that varies the increment according to the velocity the knob is turned, which is obviously considerably more complicated.

An xy pad that can output OSC directly, like TouchOSC on an iPad, or a hardware xy controller gives much better resolution and usability.

Mic