layers.md

This is the technical documentation for the "layers" block in Tangram's scene file. For a conceptual overview of the way Tangram applies styles to data, see the [[Filters Overview]] and the [[Styles Overview]].

####layers The layers element is a required top-level element in the [[scene file]]. Individual layers are defined by a layer name under this element.

layers:
    earth:
        ...

layer name

Required string. Can be anything except the [[reserved keywords|yaml#reserved keywords]]. No default.

layers:
    landuse:
        ...

layer parameters

####data Required parameter. Defines the beginning of a data block. Usable by top-level layers only. No default.

layers:
    landuse:
        data: { source: osm }

####filter Optional object or function. No default.

A filter element may be included once in any layer or sublayer. Only features matching the filter will be included in that layer (and its sublayers). For more on the filtering system, see [[Filters Overview]].

layers:
    roads:
        data: { source: osm }
        filter: { kind: highway }

####draw Required parameter. Defines the beginning of a draw block. For draw parameters, see the [[styling rules]] section.

layers:
    landuse:
        data: { source: osm }
        draw:
            ...

####sublayer name Optional string. Can be anything except the [[reserved keywords|yaml#reserved keywords]]. No default.

Defines a sublayer. Sublayers can have all layer parameters except data, and can be nested. draw and filter definitions are inherited, and match simultaneously – see the [[Filters Overview]].

layers:
    landuse:
        data: { source: osm }
        filter: ...
        draw: ...
        sublayer:
            filter: ...
            draw: ...
        sublayer2:
            filter: ...
            draw: ...
            subsublayer:
                filter: ...
                draw: ...

properties

Optional parameter. Defines the beginning of a properties block. The properties block has one kind of sub-element: custom properties, which are a key-value pair. Keys can be anything except the reserved keywords.

Custom properties may be defined here for use in filter and shader effects. These properties may be accessed through the JavaScript API, or through filter and style functions with the properties keyword, as a convenient way to allow interactivity.

buildings:
    properties:
        min-height: 30
        color: [.3, .3, .5]
    draw:
        polygons:
            filter: function() { return feature.height > properties.min-height; }
            color: function () { return properties.color; }

data parameters

####source Required string, naming one of the sources defined in the [[sources]] block.

data:
    source: osm

####layer Optional string, naming a top-level named object in the source datalayer. In Mapzen's Vector Tile Service, this is a FeatureCollection. If a layer is not specified, the layer name will be used.

data:
    source: osm
    layer: buildings

The above layer refers to the below object:

{"buildings":
    {"type":"FeatureCollection","features":[
        {"geometry":"..."}
    ]}
}

Because the layer name is the same as the name of the GeoJSON object, the data object's layer parameter can be omitted.

draw parameters

See the [[styling rules]] section.