attribute-manager.md

AttributeManager

The AttributeManager is used internally by deck.gl layers. Unless you are writing custom deck.gl layers, or you are working with some very narrow advanced performance optimization use cases, you do not need to use this class.

The AttributeManager class provides automated attribute allocations and updates.

Summary:

• keeps track of valid state for each attribute
• auto reallocates attributes when needed
• auto updates attributes with registered updater functions
• allows overriding with application supplied buffers

For more information consult the Attribute Management article.

Static Methods

setDefaultLogFunctions {#setdefaultlogfunctions}

Sets log functions to help trace or time attribute updates. Default logging uses the deck.gl logger.

Note that the app may not be in control of when update is called, so hooks are provided for update start and end.

Parameters:

• opts.onUpdateStart (Function) - callback, called before an attribute starts updating
• opts.onUpdate (Function) - callback, called when update is performed. Receives an argument message detailing the update operation.
• opts.onUpdateEnd (Function) - callback, called after an attribute is updated. Receives an argument message detailing the update operation.

Constructor

new AttributeManager({id: 'attribute-manager'});

Parameters:

• id (string, optional) - identifier (for debugging)

Methods

add {#add}

Adds attribute descriptions to the AttributeManager that describe the attributes that should be auto-calculated.

attributeManager.add({
  positions: {size: 2, accessor: 'getPosition', update: calculatePositions},
  colors: {size: 4, type: GL.UNSIGNED_BYTE, accessor: 'getColor', update: calculateColors}
});

Takes a single parameter as a map of attribute descriptor objects:

• keys are attribute names
• values are objects with attribute definitions:
  • luma.gl accessor parameters:
    • type (string, optional) - data type of the attribute, see "Remarks" section below.
    • size (number) - number of elements per vertex
    • normalized (boolean) - default false
    • integer (boolean) - WebGL2 only, default false
    • divisor (boolean, optional) - 1 if this is an instanced attribute (a.k.a. divisor). Default to 0.
  • deck.gl attribute configurations:
    • isIndexed (boolean, optional) - if this is an index attribute (a.k.a. indices). Default to false.
    • accessor (string | string[] | Function) - accessor name(s) that will trigger an update of this attribute when changed. Used with updateTriggers.
    • transform (Function, optional) - callback to process the result returned by accessor.
    • update (Function, optional) - the function to be called when data changes. If not supplied, the attribute will be auto-filled with accessor.
    • defaultValue (number | number[], optional) - Default [0, 0, 0, 0].
    • noAlloc (boolean, optional) - if this attribute should not be automatically allocated. Default to false.
  • shaderAttributes (object, optional) - If this attribute maps to multiple attributes in the vertex shader, that mapping can be defined here. All shaderAttributes will share a single buffer created based on the size parameter. This can be used to interleave attributes. Each shader attribute object may contain any of the following:
    • size (number) - number of elements per vertex
    • vertexOffset (number) - offset of the attribute by vertex (stride). Default 0.
    • elementOffset (number) - offset of the attribute by element. default 0.
    • divisor (boolean, optional) - 1 if this is an instanced attribute (a.k.a. divisor). Default to 0.

addInstanced {#addinstanced}

Shorthand for add() in which all attributes instanced field are set to true.

remove {#remove}

Removes defined attributes.

Parameters:

• attributeNames (string[]) - Array of attribute names to be removed

invalidate {#invalidate}

Mark an attribute as need update.

Parameters:

• name (string) - Either the name of the attribute, or the name of an accessor. If an name of accessor is provided, all attributes with that accessor are invalidated.
• dataRange (object, optional) - A partial range of the attribute to invalidate, in the shape of {startRow, endRow}. Start (included) and end (excluded) are indices into the data array. If not provided, recalculate the attribute for all data.

invalidateAll {#invalidateall}

Mark all attributes as need update.

Parameters:

• dataRange (object, optional) - A partial range of the attributes to invalidate, in the shape of {startRow, endRow}. Start (included) and end (excluded) are indices into the data array. If not provided, recalculate the attributes for all data.

update {#update}

Ensure all attribute buffers are updated from props or data.

attributeManager.update({
    data,
    numInstances,
    transitions,
    startIndex,
    endIndex,
    props = {},
    buffers = {},
    context = {},
    ignoreUnknownAttributes = false
});

Parameters:

• data (object) - data (iterable object)
• numInstances (number) - count of data
• buffers (object) - pre-allocated buffers
• props (object) - passed to updaters
• context (object) - Used as "this" context for updaters

Notes:

• Any preallocated buffers in "buffers" matching registered attribute names will be used. No update will happen in this case.
• Calls onUpdateStart and onUpdateEnd log callbacks before and after.

Remarks

Attribute Type

The following type values are supported for attribute definitions:

type	value array type	notes
GL.FLOAT	Float32Array
GL.DOUBLE	Float64Array	Because 64-bit floats are not supported by WebGL, the value is converted to an interleaved Float32Array before uploading to the GPU. It is exposed to the vertex shader as two attributes, <attribute_name> and <attribute_name>64Low, the sum of which is the 64-bit value.
GL.BYTE	Int8Array
GL.SHORT	Int16Array
GL.INT	Int32Array
GL.UNSIGNED_BYTE	Uint8ClampedArray
GL.UNSIGNED_SHORT	Uint16Array
GL.UNSIGNED_INT	Uint32Array

Source

modules/core/src/lib/attribute-manager.ts