GLBufferAttribute - Verge3D 用户手册 - Soft8Soft
Description: 了解如何在使用 Verge3D 制作的交互式 3D 应用程序中使用 GLBufferAttribute

# GLBufferAttribute

This buffer attribute class does not construct a VBO. Instead, it uses whatever VBO is passed in constructor and can later be altered via the buffer property.
It is required to pass additional params alongside the VBO. Those are: the GL context, the GL data type, the number of components per vertex, the number of bytes per component, and the number of vertices.
The most common use case for this class is when some kind of GPGPU calculation interferes or even produces the VBOs in question.

## Constructor

### GLBufferAttribute(buffer : WebGLBuffer, type : GLenum, itemSize : Integer, elementSize : Integer, count : Integer)

buffer — Must be a WebGLBuffer.
type — One of WebGL Data Types.
itemSize — The number of values of the array that should be associated with a particular vertex. For instance, if this attribute is storing a 3-component vector (such as a position, normal, or color), then itemSize should be 3.
elementSize — 1, 2 or 4. The corresponding size (in bytes) for the given "type" param.

- gl.FLOAT: 4
- gl.UNSIGNED_SHORT: 2
- gl.SHORT: 2
- gl.UNSIGNED_INT: 4
- gl.INT: 4
- gl.BYTE: 1
- gl.UNSIGNED_BYTE: 1

count — The expected number of vertices in VBO.

## Properties

### # .buffer : WebGLBuffer

The current WebGLBuffer instance.

### # .count : Integer

The expected number of vertices in VBO.

### # .itemSize : Integer

How many values make up each item (vertex).

### # .elementSize : Integer

Stores the corresponding size in bytes for the current type property value.

See above (constructor) for a list of known type sizes.

### # .type : GLenum

A WebGL Data Type describing the underlying VBO contents.

Set this property together with elementSize. The recommended way is using the setType method.

### # .isGLBufferAttribute : Boolean

Read-only. Always true.

## Methods

### # .setBuffer(buffer) → null

Sets the buffer property.

### # .setType(type, elementSize) → null

Sets the both type and elementSize properties.

### # .setItemSize(itemSize) → null

Sets the itemSize property.

### # .setCount(count) → null

Sets the count property.

### # .version : Integer

A version number, incremented every time the needsUpdate property is set to true.

### # .needsUpdate : Boolean

Default is false. Setting this to true increments version.

## 源代码

关于如何获取此模块的源代码，请查看 本页。