Frequently Asked Questions
How do you control it?
When using a webcam as the input device, pmidic will look for a light source in the image which
will determine the X, Y and Z values.
How is the Z value determined?
When using a webcam as the input device, the Z value is determined by the area of the light source.
A typical application would be to assign the Z value to modulation, thus allowing you to control the
"intensity" of a sound by moving the light source closer/farther from the webcam.
What are some examples of light sources that can be used?
- An LED
- An LED taped to a 3V button battery and attached to your finger using short velcro strap
- A laser pointer
- Computer screen
- Point your camera at a bright light (e.g. ceiling), and make a closed circle with your fingers
- Use your imagination!
What is Incremental mode?
This mode allows you to send MIDI control change (CC) messages (0-127) to a MIDI
device/port. These values are controlled by the X, Y and Z values calculated
from the light source detected by your webcam. The X and Y values are self-
explanatory, while the Z value is calculated based on the area of the light. The
effect is that the further the light source, the smaller the area, and vice
In addition to control messages, the Note Range setting sends note values and
functions like a theremin. You can limit the range of notes using the text boxes
labelled Min and Max on the bottom right section of pmidic.
What is Note mode?
This mode allows you send MIDI note messages whenever a light source appears in
any of the 4 quadrants of the webcam screen. Furthermore, you can enable a
sequence of up to 4 notes per quadrant. For example, set up quadrant 1 to
play the notes C, D, E and F. The first time a light source appears, the MIDI
message to play C will be sent. The next time a light appears, D will be played.
Then E, then F, then back to C again, and so on.
What is Hit mode?
This is basically the same as Note mode except there is only one quadrant. You
can sort of play air drums with it if you have a light in your hand (e.g. LED)
and you make hitting motions. With the camera pointing towards your arm, when
you lift up your arm, there is no light source. When you "hit" downwards, and
your forearm is horizontal, the light source is pointing at the camera and thus
causes it to send a MIDI note out message. In future, this mode will be removed
as it is identical to Note mode except for the number of quadrants. In future,
you will be able to choose how many quadrants (1-4) are used in Note mode.