146 lines
8.0 KiB
C
146 lines
8.0 KiB
C
/** \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.
|
|
*/
|
|
|
|
|
|
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
|
|
{
|
|
SMikkTSpaceInterface * m_pInterface; // initialized with callback functions
|
|
void * m_pUserData; // pointer to client side mesh data etc. (passed as the first parameter with every interface call)
|
|
};
|
|
|
|
// 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
|