# Expression DMX Patching

Expression DMX Patching allows you to create new DMX mappings in-place for simpler light fixtures.

Using constants (eg. 255) and variables (eg. R, G, B) delimeted by a comma you are able to express a DMX mapping in a single line.

{% embed url="<https://youtu.be/fAMdns8xrKQ>" %}

## How To Use

Use the expression, in the format below, as the Model name when setting an output/changing model.

```
NAME:EXPRESSION
```

Expression is made up of descriptions for individual DMX channels separated by a colon (,)

```
CH1,CH2,CH3,...
```

Each channel can be a full mathematical expression but you'll likely be just either entering a fixed DMX value (0-255) or referencing one of the available variables (see below for a list).

## Caveats

All variables reference only the first pixel of a fixture. Currently there is no way to expand the DMX mapping to all available pixels.

You can still map multipixel fixtures by creating two fixtures - one using this Expression mapping and the other using one of the standard RGB mappings which do expand to cover all available pixels.

## Example - RGBW Fixture

An RGBW fixture is available from the standard fixtures so this is only provided as an explanatory example.

```
RGBW:R,G,B,W
```

## Example - Claypaky HY B-EYE

Given the following DMX chart:

![](https://2803540508-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-L_2-aJC2gpx8goxEoBZ%2F-M8KL-hBJQb3tNFeN4IX%2F-M8KNv74jRoCmgo1ObzK%2Fimage.png?alt=media\&token=c584ec69-364f-4f02-8d4a-018f6ffbb6c1)

We can write the following expression as the Model name:

```
Claypaky.HY B-EYE:R,r,G,g,B,b,W,w,O,0,S,255,255,P,p,T,t,0,0,Z,0,0
```

## Available Variables

Uppercase variables yield standard value, lowercase give you the fine part for 16-bit mapping and variable with `1` suffix gives a normalized 0-1 value.

For example, Red at full value 1.0:

* `R`: 255
* `r`: 0 (no fine part)
* `R1`: 1

<table data-header-hidden><thead><tr><th width="114">Variable</th><th>Meaning</th></tr></thead><tbody><tr><td>Variable</td><td>Meaning</td></tr><tr><td><code>L</code></td><td>Dimmer, the <strong>L</strong>uminance of first pixel</td></tr><tr><td><code>R</code></td><td><strong>R</strong>ed content of first pixel</td></tr><tr><td><code>G</code></td><td><strong>G</strong>reen content of first pixel</td></tr><tr><td><code>B</code></td><td><strong>B</strong>lue content of first pixel</td></tr><tr><td><code>C</code></td><td><strong>C</strong>yan content of first pixel</td></tr><tr><td><code>M</code></td><td><strong>M</strong>agenta content of first pixel</td></tr><tr><td><code>Y</code></td><td><strong>Y</strong>ellow content of first pixel</td></tr><tr><td><code>O</code></td><td>CT<strong>O</strong> (Temperature)</td></tr><tr><td><code>P</code></td><td><strong>P</strong>an</td></tr><tr><td><code>T</code></td><td><strong>T</strong>ilt</td></tr><tr><td>W</td><td>Ya<strong>w</strong> (Not Implemented)</td></tr><tr><td><code>Z</code></td><td><strong>Z</strong>oom</td></tr><tr><td><code>F</code></td><td><strong>F</strong>ocus</td></tr><tr><td><code>I</code></td><td><strong>I</strong>ris</td></tr><tr><td><code>S</code></td><td><strong>S</strong>peed, use as Frequency for strobes for instance</td></tr><tr><td><code>D</code></td><td><strong>D</strong>uration</td></tr></tbody></table>

##

## Further Work

### Functions

The expressions are evaluated using ncalc and thus should support all standard math functions, but on top there should certainly be:

|                  |                                                     |
| ---------------- | --------------------------------------------------- |
| map(X, from, to) | Remap the normalized input value to the given range |

### Others

More variables could be added to cover more scenarios - **Suggest more!**

Colorwheels, gobo selections and similar are not supported under this proposal. However this could be covered by adding special mapping functions.