function getGlslTextureSwizzle(type) {
  if (type === MetadataType.SCALAR) {
    return ".r";
  } else if (type === MetadataType.VEC2) {
    return ".ra";
  } else if (type === MetadataType.VEC3) {
    return ".rgb";
  } else if (type === MetadataType.VEC4) {
    return "";
  }
}
Gets the GLSL swizzle when reading data from a texture.

@function

@param {MetadataType} type The {@link MetadataType}.
@returns {string} The GLSL swizzle.

@private