/**
 *  Copyright (C) 2011 by Morten S. Mikkelsen
 *
 *  This software is provided 'as-is', without any express or implied
 *  warranty.  In no event will the authors be held liable for any damages
 *  arising from the use of this software.
 *
 *  Permission is granted to anyone to use this software for any purpose,
 *  including commercial applications, and to alter it and redistribute it
 *  freely, subject to the following restrictions:
 *
 *  1. The origin of this software must not be misrepresented; you must not
 *     claim that you wrote the original software. If you use this software
 *     in a product, an acknowledgment in the product documentation would be
 *     appreciated but is not required.
 *  2. Altered source versions must be plainly marked as such, and must not be
 *     misrepresented as being the original software.
 *  3. This notice may not be removed or altered from any source distribution.
 */
 
/* Author: Morten S. Mikkelsen
 * Version: 1.0
 *
 * The files mikktspace.h and mikktspace.c are designed to be
 * stand-alone files and it is important that they are kept this way.
 * Not having dependencies on structures/classes/libraries specific
 * to the program, in which they are used, allows them to be copied
 * and used as is into any tool, program or plugin.
 * The code is designed to consistently generate the same
 * tangent spaces, for a given mesh, in any tool in which it is used.
 * This is done by performing an internal welding step and subsequently an order-independent evaluation
 * of tangent space for meshes consisting of triangles and quads.
 * This means faces can be received in any order and the same is true for
 * the order of vertices of each face. The generated result will not be affected
 * by such reordering. Additionally, whether degenerate (vertices or texture coordinates)
 * primitives are present or not will not affect the generated results either.
 * Once tangent space calculation is done the vertices of degenerate primitives will simply
 * inherit tangent space from neighboring non degenerate primitives.
 * The analysis behind this implementation can be found in my master's thesis
 * which is available for download --> http://image.diku.dk/projects/media/morten.mikkelsen.08.pdf
 * Note that though the tangent spaces at the vertices are generated in an order-independent way,
 * by this implementation, the interpolated tangent space is still affected by which diagonal is
 * chosen to split each quad. A sensible solution is to have your tools pipeline always
 * split quads by the shortest diagonal. This choice is order-independent and works with mirroring.
 * If these have the same length then compare the diagonals defined by the texture coordinates.
 * XNormal which is a tool for baking normal maps allows you to write your own tangent space plugin
 * and also quad triangulator plugin.
 */