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/* SPDX-License-Identifier: Zlib
* Copyright 2011 by Morten S. Mikkelsen. */
/** \file
* \ingroup mikktspace
*/
#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.
*/
typedef int tbool;
typedef struct SMikkTSpaceContext SMikkTSpaceContext;
typedef struct {
// Returns the number of faces (triangles/quads) on the mesh to be processed.
int (*m_getNumFaces)(const SMikkTSpaceContext *pContext);
// Returns the number of vertices on face number iFace
// iFace is a number in the range {0, 1, ..., getNumFaces()-1}
int (*m_getNumVerticesOfFace)(const SMikkTSpaceContext *pContext, const int iFace);
// returns the position/normal/texcoord of the referenced face of vertex number iVert.
// iVert is in the range {0,1,2} for triangles and {0,1,2,3} for quads.
void (*m_getPosition)(const SMikkTSpaceContext *pContext,
float fvPosOut[],
const int iFace,
const int iVert);
void (*m_getNormal)(const SMikkTSpaceContext *pContext,
float fvNormOut[],
const int iFace,
const int iVert);
void (*m_getTexCoord)(const SMikkTSpaceContext *pContext,
float fvTexcOut[],
const int iFace,
const int iVert);
// either (or both) of the two setTSpace callbacks can be set.
// The call-back m_setTSpaceBasic() is sufficient for basic normal mapping.
// This function is used to return the tangent and fSign to the application.
// fvTangent is a unit length vector.
// For normal maps it is sufficient to use the following simplified version of the bitangent
// which is generated at pixel/vertex level.
// bitangent = fSign * cross(vN, tangent);
// Note that the results are returned unindexed. It is possible to generate a new index list
// But averaging/overwriting tangent spaces by using an already existing index list WILL produce
// INCRORRECT results.
// DO NOT! use an already existing index list.
void (*m_setTSpaceBasic)(const SMikkTSpaceContext *pContext,
const float fvTangent[],
const float fSign,
const int iFace,
const int iVert);
// This function is used to return tangent space results to the application.
// fvTangent and fvBiTangent are unit length vectors and fMagS and fMagT are their
// true magnitudes which can be used for relief mapping effects.
// fvBiTangent is the "real" bitangent and thus may not be perpendicular to fvTangent.
// However, both are perpendicular to the vertex normal.
// For normal maps it is sufficient to use the following simplified version of the bitangent
// which is generated at pixel/vertex level.
// fSign = bIsOrientationPreserving ? 1.0f : (-1.0f);
// bitangent = fSign * cross(vN, tangent);
// Note that the results are returned unindexed. It is possible to generate a new index list
// But averaging/overwriting tangent spaces by using an already existing index list WILL produce
// INCRORRECT results. DO NOT! use an already existing index list.
void (*m_setTSpace)(const SMikkTSpaceContext *pContext,
const float fvTangent[],
const float fvBiTangent[],
const float fMagS,
const float fMagT,
const tbool bIsOrientationPreserving,
const int iFace,
const int iVert);
} SMikkTSpaceInterface;
struct SMikkTSpaceContext {
// initialized with callback functions
SMikkTSpaceInterface *m_pInterface;
// pointer to client side mesh data etc.
// (passed as the first parameter with every interface call)
void *m_pUserData;
};
// these are both thread safe!
// Default (recommended) fAngularThreshold is 180 degrees (which means threshold disabled)
tbool genTangSpaceDefault(const SMikkTSpaceContext *pContext);
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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