/*
---------------------------------------------------------------------------
Open Asset Import Library (assimp)
---------------------------------------------------------------------------

Copyright (c) 2006-2022, assimp team



All rights reserved.

Redistribution and use of this software in source and binary forms,
with or without modification, are permitted provided that the following
conditions are met:

* Redistributions of source code must retain the above
 copyright notice, this list of conditions and the
 following disclaimer.

* Redistributions in binary form must reproduce the above
 copyright notice, this list of conditions and the
 following disclaimer in the documentation and/or other
 materials provided with the distribution.

* Neither the name of the assimp team, nor the names of its
 contributors may be used to endorse or promote products
 derived from this software without specific prior
 written permission of the assimp team.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
---------------------------------------------------------------------------
*/

/** @file Implementation of the post processing step to calculate
 * tangents and bitangents for all imported meshes
 */

// internal headers
#include "CalcTangentsProcess.h"
#include "ProcessHelper.h"
#include <assimp/TinyFormatter.h>
#include <assimp/qnan.h>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
CalcTangentsProcess::CalcTangentsProcess() :
 configMaxAngle(float(AI_DEG_TO_RAD(45.f))), configSourceUV(0) {
 // nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
CalcTangentsProcess::~CalcTangentsProcess() = default;

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool CalcTangentsProcess::IsActive(unsigned int pFlags) const {
 return (pFlags & aiProcess_CalcTangentSpace) != 0;
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void CalcTangentsProcess::SetupProperties(const Importer *pImp) {
 ai_assert(nullptr != pImp);

 // get the current value of the property
 configMaxAngle = pImp->GetPropertyFloat(AI_CONFIG_PP_CT_MAX_SMOOTHING_ANGLE, 45.f);
 configMaxAngle = std::max(std::min(configMaxAngle, 45.0f), 0.0f);
 configMaxAngle = AI_DEG_TO_RAD(configMaxAngle);

 configSourceUV = pImp->GetPropertyInteger(AI_CONFIG_PP_CT_TEXTURE_CHANNEL_INDEX, 0);
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void CalcTangentsProcess::Execute(aiScene *pScene) {
 ai_assert(nullptr != pScene);

 ASSIMP_LOG_DEBUG("CalcTangentsProcess begin");

 bool bHas = false;
 for (unsigned int a = 0; a < pScene->mNumMeshes; a++) {
 if (ProcessMesh(pScene->mMeshes[a], a)) bHas = true;
 }

 if (bHas) {
 ASSIMP_LOG_INFO("CalcTangentsProcess finished. Tangents have been calculated");
 } else {
 ASSIMP_LOG_DEBUG("CalcTangentsProcess finished");
 }
}

// ------------------------------------------------------------------------------------------------
// Calculates tangents and bi-tangents for the given mesh
bool CalcTangentsProcess::ProcessMesh(aiMesh *pMesh, unsigned int meshIndex) {
 // we assume that the mesh is still in the verbose vertex format where each face has its own set
 // of vertices and no vertices are shared between faces. Sadly I don't know any quick test to
 // assert() it here.
 // assert( must be verbose, dammit);

 if (pMesh->mTangents) // this implies that mBitangents is also there
 return false;

 // If the mesh consists of lines and/or points but not of
 // triangles or higher-order polygons the normal vectors
 // are undefined.
 if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON))) {
 ASSIMP_LOG_INFO("Tangents are undefined for line and point meshes");
 return false;
 }

 // what we can check, though, is if the mesh has normals and texture coordinates. That's a requirement
 if (pMesh->mNormals == nullptr) {
 ASSIMP_LOG_ERROR("Failed to compute tangents; need normals");
 return false;
 }
 if (configSourceUV >= AI_MAX_NUMBER_OF_TEXTURECOORDS || !pMesh->mTextureCoords[configSourceUV]) {
 ASSIMP_LOG_ERROR("Failed to compute tangents; need UV data in channel", configSourceUV);
 return false;
 }

 const float angleEpsilon = 0.9999f;

 std::vector<bool> vertexDone(pMesh->mNumVertices, false);
 const float qnan = get_qnan();

 // create space for the tangents and bitangents
 pMesh->mTangents = new aiVector3D[pMesh->mNumVertices];
 pMesh->mBitangents = new aiVector3D[pMesh->mNumVertices];

 const aiVector3D *meshPos = pMesh->mVertices;
 const aiVector3D *meshNorm = pMesh->mNormals;
 const aiVector3D *meshTex = pMesh->mTextureCoords[configSourceUV];
 aiVector3D *meshTang = pMesh->mTangents;
 aiVector3D *meshBitang = pMesh->mBitangents;

 // calculate the tangent and bitangent for every face
 for (unsigned int a = 0; a < pMesh->mNumFaces; a++) {
 const aiFace &face = pMesh->mFaces[a];
 if (face.mNumIndices < 3) {
 // There are less than three indices, thus the tangent vector
 // is not defined. We are finished with these vertices now,
 // their tangent vectors are set to qnan.
 for (unsigned int i = 0; i < face.mNumIndices; ++i) {
 unsigned int idx = face.mIndices[i];
 vertexDone[idx] = true;
 meshTang[idx] = aiVector3D(qnan);
 meshBitang[idx] = aiVector3D(qnan);
 }

 continue;
 }

 // triangle or polygon... we always use only the first three indices. A polygon
 // is supposed to be planar anyways....
 // FIXME: (thom) create correct calculation for multi-vertex polygons maybe?
 const unsigned int p0 = face.mIndices[0], p1 = face.mIndices[1], p2 = face.mIndices[2];

 // position differences p1->p2 and p1->p3
 aiVector3D v = meshPos[p1] - meshPos[p0], w = meshPos[p2] - meshPos[p0];

 // texture offset p1->p2 and p1->p3
 float sx = meshTex[p1].x - meshTex[p0].x, sy = meshTex[p1].y - meshTex[p0].y;
 float tx = meshTex[p2].x - meshTex[p0].x, ty = meshTex[p2].y - meshTex[p0].y;
 float dirCorrection = (tx * sy - ty * sx) < 0.0f ? -1.0f : 1.0f;
 // when t1, t2, t3 in same position in UV space, just use default UV direction.
 if (sx * ty == sy * tx) {
 sx = 0.0;
 sy = 1.0;
 tx = 1.0;
 ty = 0.0;
 }

 // tangent points in the direction where to positive X axis of the texture coord's would point in model space
 // bitangent's points along the positive Y axis of the texture coord's, respectively
 aiVector3D tangent, bitangent;
 tangent.x = (w.x * sy - v.x * ty) * dirCorrection;
 tangent.y = (w.y * sy - v.y * ty) * dirCorrection;
 tangent.z = (w.z * sy - v.z * ty) * dirCorrection;
 bitangent.x = (- w.x * sx + v.x * tx) * dirCorrection;
 bitangent.y = (- w.y * sx + v.y * tx) * dirCorrection;
 bitangent.z = (- w.z * sx + v.z * tx) * dirCorrection;

 // store for every vertex of that face
 for (unsigned int b = 0; b < face.mNumIndices; ++b) {
 unsigned int p = face.mIndices[b];

 // project tangent and bitangent into the plane formed by the vertex' normal
 aiVector3D localTangent = tangent - meshNorm[p] * (tangent * meshNorm[p]);
 aiVector3D localBitangent = bitangent - meshNorm[p] * (bitangent * meshNorm[p]) - localTangent * (bitangent * localTangent);
 localTangent.NormalizeSafe();
 localBitangent.NormalizeSafe();

 // reconstruct tangent/bitangent according to normal and bitangent/tangent when it's infinite or NaN.
 bool invalid_tangent = is_special_float(localTangent.x) || is_special_float(localTangent.y) || is_special_float(localTangent.z);
 bool invalid_bitangent = is_special_float(localBitangent.x) || is_special_float(localBitangent.y) || is_special_float(localBitangent.z);
 if (invalid_tangent != invalid_bitangent) {
 if (invalid_tangent) {
 localTangent = meshNorm[p] ^ localBitangent;
 localTangent.NormalizeSafe();
 } else {
 localBitangent = localTangent ^ meshNorm[p];
 localBitangent.NormalizeSafe();
 }
 }

 // and write it into the mesh.
 meshTang[p] = localTangent;
 meshBitang[p] = localBitangent;
 }
 }

 // create a helper to quickly find locally close vertices among the vertex array
 // FIX: check whether we can reuse the SpatialSort of a previous step
 SpatialSort *vertexFinder = nullptr;
 SpatialSort _vertexFinder;
 float posEpsilon = 10e-6f;
 if (shared) {
 std::vector<std::pair<SpatialSort, float>> *avf;
 shared->GetProperty(AI_SPP_SPATIAL_SORT, avf);
 if (avf) {
 std::pair<SpatialSort, float> &blubb = avf->operator[](meshIndex);
 vertexFinder = &blubb.first;
 posEpsilon = blubb.second;
 ;
 }
 }
 if (!vertexFinder) {
 _vertexFinder.Fill(pMesh->mVertices, pMesh->mNumVertices, sizeof(aiVector3D));
 vertexFinder = &_vertexFinder;
 posEpsilon = ComputePositionEpsilon(pMesh);
 }
 std::vector<unsigned int> verticesFound;

 const float fLimit = std::cos(configMaxAngle);
 std::vector<unsigned int> closeVertices;

 // in the second pass we now smooth out all tangents and bitangents at the same local position
 // if they are not too far off.
 for (unsigned int a = 0; a < pMesh->mNumVertices; a++) {
 if (vertexDone[a])
 continue;

 const aiVector3D &origPos = pMesh->mVertices[a];
 const aiVector3D &origNorm = pMesh->mNormals[a];
 const aiVector3D &origTang = pMesh->mTangents[a];
 const aiVector3D &origBitang = pMesh->mBitangents[a];
 closeVertices.resize(0);

 // find all vertices close to that position
 vertexFinder->FindPositions(origPos, posEpsilon, verticesFound);

 closeVertices.reserve(verticesFound.size() + 5);
 closeVertices.push_back(a);

 // look among them for other vertices sharing the same normal and a close-enough tangent/bitangent
 for (unsigned int b = 0; b < verticesFound.size(); b++) {
 unsigned int idx = verticesFound[b];
 if (vertexDone[idx])
 continue;
 if (meshNorm[idx] * origNorm < angleEpsilon)
 continue;
 if (meshTang[idx] * origTang < fLimit)
 continue;
 if (meshBitang[idx] * origBitang < fLimit)
 continue;

 // it's similar enough -> add it to the smoothing group
 closeVertices.push_back(idx);
 vertexDone[idx] = true;
 }

 // smooth the tangents and bitangents of all vertices that were found to be close enough
 aiVector3D smoothTangent(0, 0, 0), smoothBitangent(0, 0, 0);
 for (unsigned int b = 0; b < closeVertices.size(); ++b) {
 smoothTangent += meshTang[closeVertices[b]];
 smoothBitangent += meshBitang[closeVertices[b]];
 }
 smoothTangent.Normalize();
 smoothBitangent.Normalize();

 // and write it back into all affected tangents
 for (unsigned int b = 0; b < closeVertices.size(); ++b) {
 meshTang[closeVertices[b]] = smoothTangent;
 meshBitang[closeVertices[b]] = smoothBitangent;
 }
 }
 return true;
}