Light Painting application
For doing light painting, you have to use the ArKaos plugin which can be used with
ArKaos GrandVJ, ArKaos Media Master and ArKaos NuVJ.
There are two versions of the plugin that propose different parameters. One may fit
better your setup, it depends on ambient luminosity and targeted lighting objects
- "Light Painting": proposes 3 parameters:
- "Threshold": The minimum luminosity to accept the light source in the
picture. Pixels with luminosity below threshold will be ignored.
- "Release Speed": The fade to black speed (zero for infinite presentation
- "Reset": if more than 50%, will reset the buffer to black. You can map a
key (ie space bar) to this parameter to be able to reset fastly the picture)
- "Light Painting B/C" ("B/C" for Brightness/Contrast) proposes 4 parameters:
- "Brightness": descreases the brightness of the picture, so it is a kind of
threshold because if you set it to 50%, the luminosity of all pixels will decrease of
50% and all pixels below 50% luminosity will become black.
- "Contrast": multiplies the pixels luminosity, after reducing the brightness,
pixels become more dark. Setting the contrast value will allow you to scale final
luminosity depending on your video signal.
- "Release Speed": Same as above.
- "Reset": Same as above.
I noticed doing experimentations that the second version of the plugin gives
smoother picture and seems nicer so I recommend you to use this one. But you are
free to give a try to the other one. The fact is, depending on your camera, you
lighting environment and the objects you want to track, you will have to experiment
with those plugins and find the good one and the right values.
In the application, the plugins are in the Effects / XP category.
While experimenting to see if we were getting the best effect, I tried to make a
standalone application that reproduces the behavior, but using Apple libraries
directly. I succeed getting this application fully functional and provide it to you as
well. It seems that the camera input is a little more fluid in this application than in
GrandVJ (it depends on the camera device driver) so it may be useful. For me with
the MacBook Pro webcam, I get a perfect result in both GrandVJ and standalone
app. But with a Sony DV camera it appears to be nicer in the standalone application.
Of couse, I cannot modify or see what happens in GrandVJ. So I provide you both
solution and you can, depending on the situation, use one or another. The plugin
should be good for your show, but you are free to use this application also.
Here is how the application works:
The application "Light Painting Default Cam.app" will start fullscreen display and will
directly apply the effect. It opens the default camera. If you have only one input,
there's no problem. On a Mac where you would have an internal webcam and a USB
or PCI input solution, you would have to choose which one to use. There's no
system setting to select the default video device, however the device you selected to
use in iChat will be the default (you have to quit iChat after selecting your camera,
otherwise it will be locked for all other applications).
The application "Light Painting DV-VCR.app" works the same but using the DV video
device connected, except if there is none, in this case uses the default input device.
The application offers settings like in arKaos:
- Left and right arrow keys lets you define the "Release speed" or fade to black
- "R" key will reset the "release speed" to 0 so it makes infinite presentation of the
- Up and down arrow keys lets you define threshold (it uses brightness and
contrast settings for nicer effect)
- Space bar resets the picture to black.
- "S" key (for "Source") enables or disables the display of the source picture in
Please feel free to contact me at any time.
Video and Lighting – Software Development – Service & Expertise