Chapter 656: GLBufferAttribute

Core Idea

An alternative version of a buffer attribute with more control over the VBO.

The renderer does not construct a VBO for this kind of attribute. Instead, it uses whatever VBO is passed in constructor and can later be altered via the buffer property.

The most common use case for this class is when some kind of GPGPU calculation interferes or even produces the VBOs in question.

Notice that this class can only be used with WebGLRenderer.

Key Concepts

buffer : WebGLBuffer: The native WebGL buffer.
count : number: The expected number of vertices in VBO.
elementSize : number: The corresponding size (in bytes) for the given type parameter.
isGLBufferAttribute : boolean (readonly): This flag can be used for type testing.
itemSize : number: The item size, see BufferAttribute#itemSize.
name : string: The name of the buffer attribute.
needsUpdate : number: Flag to indicate that this attribute has changed and should be re-sent to the GPU. Set this to true when you modify the value of the arra…
normalized : boolean: Applies to integer data only. Indicates how the underlying data in the buffer maps to the values in the GLSL code. For instance, if `buffer…
type : number: The native data type.
version : number: A version number, incremented every time the needsUpdate is set to true.

Reference Tables

Constructor

Signature
`new GLBufferAttribute( buffer : WebGLBuffer, type : number, itemSize : number, elementSize : number, count : number, normalized : boolean )`

Properties

Property	Description
`.buffer : WebGLBuffer`	The native WebGL buffer.
`.count : number`	The expected number of vertices in VBO.
`.elementSize : number`	The corresponding size (in bytes) for the given `type` parameter.
`.isGLBufferAttribute : boolean (readonly)`	This flag can be used for type testing.
`.itemSize : number`	The item size, see BufferAttribute#itemSize.
`.name : string`	The name of the buffer attribute.
`.needsUpdate : number`	Flag to indicate that this attribute has changed and should be re-sent to the GPU. Set this to `true` when you modify the value of the array.
`.normalized : boolean`	Applies to integer data only. Indicates how the underlying data in the buffer maps to the values in the GLSL code. For instance, if `buffer` contains data of `gl.UNSIGNED_SHORT`, and `normalized` is …
`.type : number`	The native data type.
`.version : number`	A version number, incremented every time the `needsUpdate` is set to `true`.

Methods

Method	Description
`.setBuffer( buffer : WebGLBuffer ) : BufferAttribute`	Sets the given native WebGL buffer.
`.setCount( count : number ) : BufferAttribute`	Sets the count (the expected number of vertices in VBO).
`.setItemSize( itemSize : number ) : BufferAttribute`	Sets the item size.
`.setType( type : number, elementSize : number ) : BufferAttribute`	Sets the given native data type and element size.

Key Takeaways

Most relevant properties: buffer, count, elementSize, isGLBufferAttribute.
Key methods: setBuffer, setCount, setItemSize, setType.

Connects To

Source: src/core/GLBufferAttribute.js