Source: \core\utils\createIndicesForQuads.js

    /**
 * Generic Mask Stack data structure
 *
 * @memberof PIXI
 * @function createIndicesForQuads
 * @private
 * @param {number} size - Number of quads
 * @return {Uint16Array} indices
 */
export default function createIndicesForQuads(size)
{
    // the total number of indices in our array, there are 6 points per quad.

    const totalIndices = size * 6;

    const indices = new Uint16Array(totalIndices);

    // fill the indices with the quads to draw
    for (let i = 0, j = 0; i < totalIndices; i += 6, j += 4)
    {
        indices[i + 0] = j + 0;
        indices[i + 1] = j + 1;
        indices[i + 2] = j + 2;
        indices[i + 3] = j + 0;
        indices[i + 4] = j + 2;
        indices[i + 5] = j + 3;
    }

    return indices;
}