Texture

A Texture is a WebGL object that contains one or more images that all have the same image format. Shaders can read from textures (through a sampler uniform) and they can be set up as render targets (by attaching them to a framebuffer).

Note: This section describes the Texture base class that implements functionality common to all four types of WebGL:

• Texture2D - Contains a "normal" image texture
• TextureCube - Holds 6 textures representing sides of a cube.
• Texture3D (WebGL 2) - Holds a "stack" of textures which enables 3D interpolation.

For more details see OpenGL Wiki.

Note that textures have a lot of optional capabilities made available by extensions, see the Limits section below.

Usage

• For additional usage examples, Texture inherits from Resource.

Configuring a Texture

const texture = new Texture2D(gl);
texture.setParameters({
  [GL.TEXTURE_WRAP_S]: GL.CLAMP
});

Using Textures

const texture = new Texture2D(gl, ...);

// For ease of use, the `Model` class can bind textures for a draw call
model.draw({
  uniforms({uMVMatrix: matrix, texture1: texture, texture2: texture})
});

// Alternatively, bind the textures using the `Texture` API directly
texture.bind(0);
texture.bind(1);
model.draw({
  uniforms({uMVMatrix: matrix})
});

Members

A number of read only accessors are available:

• width - width of one face of the cube map

• height - height of one face of the cube map

• format - internal format of the face textures

• border - Always 0.

• type - type used to create face textures

• dataFormat - data format used to create face textures.

• offset - offset used to create face textures. Always 0, unless specified using WebGL 2 buffer constructor.

• handle - The underlying WebGL object.

• id - An identifying string that is intended to help debugging.

Sampler parameters can be accessed using Texture.getParameter, e.g:

texture.getParameter(GL.TEXTURE_MAG_FILTER);

Methods

constructor(gl : WebGLRenderingContext, props : Object)

The texture class cannot be constructed directly. It is a base class that provides common methods the the concrete texture classes.

• Texture2D,
• TextureCube and
• Texture3D.

The constructors for these classes should be used to create textures. They constructors all take common parameters, many of which are specified in this document.

• Pixel store parameters are described in State Management.

resize(options : Object) : Texture2D

Call to resize a texture. If size has changed, reinitializes texture with current format. Note: calling resize clears image and mipmaps.

• width (GLint) - width to resize to.
• height (GLint) - height to resize to.
• mipmaps (bool) - turn on/off mipmapping. default false.

generateMipmap() : Texture2D

Call to regenerate mipmaps after modifying texture(s)

WebGL References gl.generateMipmap

setImageData(options : Object) : Texture2D

Allocates storage and sets image data

  Texture.setImageData({
    target = this.target,
    pixels = null,
    data = null,
    width,
    height,
    level = 0,
    format = GL.RGBA,
    type,
    dataFormat,
    offset = 0,
    border = 0,
    compressed = false,
    parameters= {}
  });

• data (*) - Image data. Can be one of several data types see table below
• pixels (*) - alternative to data
• width (GLint) -
• height (GLint) -
• level (GLint) -
• format (GLenum) - format of image data.
• type (GLenum)

• format of array (autodetect from type) or
• (WEBGL2) format of buffer

• offset (Number) - (WEBGL2) offset from start of buffer
• border (GLint) - must be 0.
• compressed (Boolean) -
• parameters (Object) - GL parameters to be temporarily applied (most of the time, pixelStorage parameters) when updating the texture.

Valid image data types:

• null - create empty texture of specified format
• Typed array - initializes from image data in typed array according to format
• Buffer|WebGLBuffer - (WEBGL2) initialized from image data in WebGLBuffer accoeding to format.
• HTMLImageElement|Image - Initializes with content of image. Auto deduces texture width/height from image.
• HTMLCanvasElement - Inits with contents of canvas. Auto width/height.
• HTMLVideoElement - Creates video texture that continuously updates. Auto width/height.

setSubImageData(options : Object) : Texture2D

Redefines an area of an existing texture Note: does not allocate storage

  Texture.setSubImageData({
    target = this.target,
    pixels = null,
    data = null,
    x = 0,
    y = 0,
    width,
    height,
    level = 0,
    format = GL.RGBA,
    type,
    dataFormat,
    compressed = false,
    offset = 0,
    border = 0,
    parameters = {}
  });

• x (GLint) - xOffset from where texture to be updated
• y (GLint) - yOffset from where texture to be updated
• width (GLint) - width of the sub image to be updated
• height (GLint) - height of the sub image to be updated
• level (GLint) - mip level to be updated
• format (GLenum) - internal format of image data.
• typ (GLenum) - format of array (autodetect from type) or (WEBGL2) format of buffer or ArrayBufferView
• dataFormat (GLenum) - format of image data.
• offset (Number) - (WEBGL2) offset from start of buffer
• border (GLint) - must be 0.
• parameters - temporary settings to be applied, can be used to supply pixel store settings.

See also gl.compressedTexSubImage2D, gl.texSubImage2D, gl.bindTexture, gl.bindBuffer

update()

Update this texture if HTMLVideoElement is used as the data source. This method is automatically called before every draw call if this texture is bound to a uniform.

getActiveUnit()

Returns number of active textures.

bind()

Binds itself to given textureUnit.

The following WebGL APIs are called in the function gl.activeTexture, gl.bindTexture

unbind()

The following WebGL APIs are called in the function gl.activeTexture, gl.bindTexture

Texture Image Data

WebGL allows textures to be created from a number of different data sources.

Texture Formats

Internal Format

If an application wants to store the texture at a certain resolution or in a certain format, it can request the resolution and format with internalFormat. WebGL will choose an internal representation with least the internal component sizes, and exactly the component types shown for that format, although it may not match exactly.

WebGL 2 adds sized internal formats which enables the application to request specific components sizes and types (float and integer formats). While sized formats offer more control, unsized formats do give the GPU freedom to select the most performant internal representation.

Texture Component Type

Describes the layout of each color component in memory.

Texture Format Combinations

This a simplified table illustrating what combinations of internal formats work with what data formats and types. Note that luma.gl deduces dataFormat and type from format by taking the first value from the data format and data type entries in this table.

For more details, see tables in:

• WebGL 2 spec
• OpenGL ES spec

Limits and Capabilities

NPOT Textures (WebGL 1)

• Any texture with a non power of two dimension (width or height) is referred as NPOT texture, under WebGL 1 NPOT textures have following limitations.

• 'Texture' class will perform above settings when NPOT texture resource is created. When un-supported filtering is set using Texture.setParameters, those will be overwritten with above supported values (GL.TEXTURE_MIN_FILTER will be set to GL.LINEAR). This only happens for NPOT textures when using WebGL 1, and a warning log will be printed every time a setting is overwritten.

Remarks

• Textures can be supplied as uniforms to shaders that can sample them using texture coordinates and color pixels accordingly.
• Parameters that affect texture sampling can be set on textures or sampler objects.
• Textures can be created from a number of different sources, including typed arrays, HTML Images, HTML Canvases, HTML Videos and WebGLBuffers (WebGL 2).
• The WebGL Context has global "pixel store" parameters that control how pixel data is laid out, including Y direction, color space etc.
• Textures are read from supplied data and written to the specified format/type parameters and pixel store parameters.