WEBGL_compressed_texture_s3tc

The WEBGL_compressed_texture_s3tc extension is part of the WebGL API and exposes four S3TC compressed texture formats.

Compressed textures reduce the amount of memory needed to store a texture on the GPU, allowing for higher resolution textures or more of the same resolution textures.

WebGL extensions are available using the WebGLRenderingContext.getExtension() method. For more information, see also Using Extensions in the WebGL tutorial.

Constants

The compressed texture formats are exposed by four constants and can be used in two functions: compressedTexImage2D() and compressedTexSubImage2D().

ext.COMPRESSED_RGB_S3TC_DXT1_EXT

A DXT1-compressed image in an RGB image format.

ext.COMPRESSED_RGBA_S3TC_DXT1_EXT

A DXT1-compressed image in an RGB image format with a simple on/off alpha value.

ext.COMPRESSED_RGBA_S3TC_DXT3_EXT

A DXT3-compressed image in an RGBA image format. Compared to a 32-bit RGBA texture, it offers 4:1 compression.

ext.COMPRESSED_RGBA_S3TC_DXT5_EXT

A DXT5-compressed image in an RGBA image format. It also provides a 4:1 compression, but differs to the DXT3 compression in how the alpha compression is done.

Examples

var ext = (
  gl.getExtension("WEBGL_compressed_texture_s3tc") ||
  gl.getExtension("MOZ_WEBGL_compressed_texture_s3tc") ||
  gl.getExtension("WEBKIT_WEBGL_compressed_texture_s3tc")
);

var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);

gl.compressedTexImage2D(gl.TEXTURE_2D, 0, ext.COMPRESSED_RGBA_S3TC_DXT5_EXT, 512, 512, 0, textureData); 

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);

Specifications

Browser compatibility

[1] This extension was prefixed with MOZ_ from version 15 to version 21.

See also

• S3 Texture Compression – OpenGL wiki
• WebGLRenderingContext.getExtension()
• WebGLRenderingContext.compressedTexImage2D()
• WebGLRenderingContext.compressedTexSubImage2D()
• WebGLRenderingContext.getParameter()