Introduction
We call it Pixel Mapping when we slice up an image into a relatively small number of pieces, then take the average color of each slice, and send it to an RGB fixture matrix device, usually via DMX.
Using Unreal Engine
If your project is already using Unreal Engine, then one way to do Pixel Mapping is using Unreal's own DMX tools. Please consult this documentation.
If you need to map a video content coming from Aximmetry, please check Additional Control with Blueprints, especially the Get Aximmetry Video section on how to transfer video from Aximmetry to Unreal Engine.
Using Aximmetry Flow Graph
You can do the Pixel Mapping natively in Aximmetry as well. Use the helper compound [Common]:Compounds\DMX\DMX_Pixel_Mapper.xcomp for that purpose.
Preview images
The module has two video outputs, Monitor and Preview. These can be useful while setting up the mapping, but the are not needed during the production, since the actual output of the module is the DMX signal.
During setting up you can optionally wire these pins to either one of your outputs, or a preview panel.
The Monitor view shows the division of the input image:
The Preview view shows a schematic appearance of the fixture matrix, colored with the current image contents:
Setting up the division
The first step is specifying the number of Columns and Rows of the fixture matrix. It is common that these devices have 5 x 5 fixtures, but can also be a single row, like 4 x 1.
NOTE: the DMX_Pixel_Mapper compound is currently set to handle a maximum of 25 fixtures. If you need more, open up the compound, right-click on the Block module, and select Setup Array. Then set the maximum number of fixtures you need. Please do not set a higher number than your actual needs, because it can result in performance degradation. Then you also have to extend the number list in the Fixture Mapping property in order to contain at least as many indices as the number of used fixtures. See more on this property below.
You can setup a Padding of you only want to average a smaller inner part of each slice:
Use Offset and Scale if you only need to map a smaller part of the image:
Mapping the fixtures
By turning on Show Numbers you can see which image slice is assigned to which fixture.
On the Monitor view, you can see the automatic numbering of the image slices, which is always continuous row-major.
On the Preview view, you can see for each fixture which image slice it is assigned to:
As you can see, the default mapping specifies an identical order. In some cases you may want a different mapping order. You can specify it using the Fixture Mapping property.
For example, if you want fixture 4 have the color of slice 23, then replace the 4th element in the list with 23:
DMX settings
Specify the DMX Device, Net, Subnet, Universe properties according to the settings of the fixture matrix device:
Starting from Start Channel, each fixture will use up 4 DMX channels (RGBW), meaning the total number of used DMX channels will be Columns x Rows x 4.
Please see more info in Using DMX with Aximmetry.
NOTE 1: the fixture matrix device has to be set to the proper mode to work this way. For example, an 5 x 5 device will have something like "100 channel mode", or "102 channel mode", please select it.
NOTE 2: the compound assumes that the fixture matrix device expects RGBW values, meaning four DMX channels per fixture, mapped consecutively in the channel space. The compound only sends the RGB values, setting all W channels to zero. If you need a differend configuration, please open up the compound, go inside the Block module, find the DMX Color Out module, and implement a different Channel number, or color value calculation method in the Flow Graph.
