/** \file mikktspace/mikktspace.h * \ingroup mikktspace */ /** * 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. */ #ifndef __MIKKTSPACE_H__ #define __MIKKTSPACE_H__ #ifdef __cplusplus extern "C" { #endif /* 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. */ tbool; SMikkTSpaceContext; SMikkTSpaceInterface; struct SMikkTSpaceContext { … }; // these are both thread safe! tbool genTangSpaceDefault(const SMikkTSpaceContext * pContext); // Default (recommended) fAngularThreshold is 180 degrees (which means threshold disabled) tbool genTangSpace(const SMikkTSpaceContext * pContext, const float fAngularThreshold); // To avoid visual errors (distortions/unwanted hard edges in lighting), when using sampled normal maps, the // normal map sampler must use the exact inverse of the pixel shader transformation. // The most efficient transformation we can possibly do in the pixel shader is // achieved by using, directly, the "unnormalized" interpolated tangent, bitangent and vertex normal: vT, vB and vN. // pixel shader (fast transform out) // vNout = normalize( vNt.x * vT + vNt.y * vB + vNt.z * vN ); // where vNt is the tangent space normal. The normal map sampler must likewise use the // interpolated and "unnormalized" tangent, bitangent and vertex normal to be compliant with the pixel shader. // sampler does (exact inverse of pixel shader): // float3 row0 = cross(vB, vN); // float3 row1 = cross(vN, vT); // float3 row2 = cross(vT, vB); // float fSign = dot(vT, row0)<0 ? -1 : 1; // vNt = normalize( fSign * float3(dot(vNout,row0), dot(vNout,row1), dot(vNout,row2)) ); // where vNout is the sampled normal in some chosen 3D space. // // Should you choose to reconstruct the bitangent in the pixel shader instead // of the vertex shader, as explained earlier, then be sure to do this in the normal map sampler also. // Finally, beware of quad triangulations. If the normal map sampler doesn't use the same triangulation of // quads as your renderer then problems will occur since the interpolated tangent spaces will differ // eventhough the vertex level tangent spaces match. This can be solved either by triangulating before // sampling/exporting or by using the order-independent choice of diagonal for splitting quads suggested earlier. // However, this must be used both by the sampler and your tools/rendering pipeline. #ifdef __cplusplus } #endif #endif
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