Light Mixer has a custom Qt-based user interface that takes over the parameter editor when this node is selected. You can switch between the custom interface and the regular parameters by clicking the Show/hide parameters button in the Parameter editor’s toolbar.

• A tree on the left shows all lights in the scene.

• Drag one or more lights or collections from the tree on the left into the space on the right.

• You can switch the right side between two views of the added lights:

  Sliders

  Build a custom mixer interface, showing the lights and collections as sliders, similar to a light board.

  Sheet

  Displays the attributes on the lights in a spreadsheet format.

• If you drag in an individual light into the mixer, it appears as an individual set of sliders for controlling different attributes (intensity and exposure, by default, plus color).

  In the spreadsheet view, individual lights appear as rows.

• If you drag a light collection into the mixer, it first appears collapsed. Click the Collapse button in the top right corner to expand the lights inside.

  Each collection has its own “master sliders” for intensity, exposure, and a tint color, which are all multiplied with the attributes of the lights inside.

  In the spreadsheet, collections appear as folders with light rows under them.

• This node represents a first try at using custom Python-driven UI for a node. Future versions should be faster, more robust, and have many more features.

• Currently collections are always created on /collection.

• Collections created here will not have “/” included by default and their expansion rule is explicitOnly.

• You can add the same light/collection multiple times.

You can customize the Light Mixer user interface by creating a HOUDINIPATH/LightMixerConfig.json file (for example, $HOUDINI_USER_PREF_DIR/LightMixerConfig.json. If the node finds multiple LightMixerConfig.json files on the path, it merges them such that files earlier in the path override later ones (the HOUDINIPATH is ordered from most specific to least specific, unlike many path variables in UNIX where later items override earlier ones).

The following example contains the defaults for the available settings:

{
    "main.default_tab": 1,
    "mixer.show_attributes": ["inputs:intensity", "intputs:exposure"],
    "sheet.show_attributes": ["inputs:intensity", "inputs:exposure", "inputs:color",
                              "inputs:colorTemperature", "$solo", "$mute", "$active"],
    "collections.search": ["/lights", "/collections"],
    "lights.search": ["/"],
    "attributes.config": { }
}

In your configuration file you can omit default values (unless you need to override another configuration file higher up the path). For example, if you only want to make new Light Mixers open with the Attribute Spreadsheet tab active, you can use just the following:

{
    "main.default_tab": 0
}

You can use the following configuration keys in the JSON file:

{
    "sheet.show_attributes": ["inputs:intensity", "mycustomvector"],
    "attributes.config": {
        "mycustomvector": {
            "type": "float2",
            "default": [1.0, 1.5], 
            "identity": [1.0, 1.0],
            "min": 0.0, 
            "max": 3.0, 
            "label": "Size", 
            "component_labels": ["Width", "Height"],
            "modify": "multiply", 
            "precision": 0.1, 
        }
    }
}