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*/

/** @file Implementation of the post processing step to generate face

* normals for all imported faces.

*/

// internal headers

#include "GenVertexNormalsProcess.h"

#include "ProcessHelper.h"

#include <assimp/Exceptional.h>

#include <assimp/qnan.h>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------

// Constructor to be privately used by Importer

GenVertexNormalsProcess::GenVertexNormalsProcess() :

        configMaxAngle(AI_DEG_TO_RAD(175.f)) {

    // empty

}

// ------------------------------------------------------------------------------------------------

// Returns whether the processing step is present in the given flag field.

bool GenVertexNormalsProcess::IsActive(unsigned int pFlags) const {

    force_ = (pFlags & aiProcess_ForceGenNormals) != 0;

    flippedWindingOrder_ = (pFlags & aiProcess_FlipWindingOrder) != 0;

    leftHanded_ = (pFlags & aiProcess_MakeLeftHanded) != 0;

    return (pFlags & aiProcess_GenSmoothNormals) != 0;

}

// ------------------------------------------------------------------------------------------------

// Executes the post processing step on the given imported data.

void GenVertexNormalsProcess::SetupProperties(const Importer *pImp) {

    // Get the current value of the AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE property

    configMaxAngle = pImp->GetPropertyFloat(AI_CONFIG_PP_GSN_MAX_SMOOTHING_ANGLE, (ai_real)175.0);

    configMaxAngle = AI_DEG_TO_RAD(std::max(std::min(configMaxAngle, (ai_real)175.0), (ai_real)0.0));

}

// ------------------------------------------------------------------------------------------------

// Executes the post processing step on the given imported data.

void GenVertexNormalsProcess::Execute(aiScene *pScene) {

    ASSIMP_LOG_DEBUG("GenVertexNormalsProcess begin");

    if (pScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT) {

        throw DeadlyImportError("Post-processing order mismatch: expecting pseudo-indexed (\"verbose\") vertices here");

    }

    bool bHas = false;

    for (unsigned int a = 0; a < pScene->mNumMeshes; ++a) {

        if (GenMeshVertexNormals(pScene->mMeshes[a], a))

            bHas = true;

    }

    if (bHas) {

        ASSIMP_LOG_INFO("GenVertexNormalsProcess finished. "

                        "Vertex normals have been calculated");

    } else {

        ASSIMP_LOG_DEBUG("GenVertexNormalsProcess finished. "

                         "Normals are already there");

    }

}

// ------------------------------------------------------------------------------------------------

// Executes the post processing step on the given imported data.

bool GenVertexNormalsProcess::GenMeshVertexNormals(aiMesh *pMesh, unsigned int meshIndex) {

    if (nullptr != pMesh->mNormals) {

        if (!force_) {

            return false;

        }

        delete[] pMesh->mNormals;

        pMesh->mNormals = nullptr;

    }

    // 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("Normal vectors are undefined for line and point meshes");

        return false;

    }

    // Allocate the array to hold the output normals

    const float qnan = std::numeric_limits<ai_real>::quiet_NaN();

    pMesh->mNormals = new aiVector3D[pMesh->mNumVertices];

    // Compute per-face normals but store them per-vertex

    for (unsigned int a = 0; a < pMesh->mNumFaces; a++) {

        const aiFace &face = pMesh->mFaces[a];

        if (face.mNumIndices < 3) {

            // either a point or a line -> no normal vector

            for (unsigned int i = 0; i < face.mNumIndices; ++i) {

                pMesh->mNormals[face.mIndices[i]] = aiVector3D(qnan);

            }

            continue;

        }

        const aiVector3D *pV1 = &pMesh->mVertices[face.mIndices[0]];

        const aiVector3D *pV2 = &pMesh->mVertices[face.mIndices[1]];

        const aiVector3D *pV3 = &pMesh->mVertices[face.mIndices[face.mNumIndices - 1]];

        // Boolean XOR - if either but not both of these flags is set, then the winding order has

        // changed and the cross product to calculate the normal needs to be reversed

        if (flippedWindingOrder_ != leftHanded_) {

            std::swap(pV2, pV3);

        }

        const aiVector3D vNor = ((*pV2 - *pV1) ^ (*pV3 - *pV1)).NormalizeSafe();

        for (unsigned int i = 0; i < face.mNumIndices; ++i) {

            pMesh->mNormals[face.mIndices[i]] = vNor;

        }

    }

    // Set up a SpatialSort to quickly find all vertices close to a given position

    // check whether we can reuse the SpatialSort of a previous step.

    SpatialSort *vertexFinder = nullptr;

    SpatialSort _vertexFinder;

    ai_real posEpsilon = ai_real(1e-5);

    if (shared) {

        std::vector<std::pair<SpatialSort, ai_real>> *avf;

        shared->GetProperty(AI_SPP_SPATIAL_SORT, avf);

        if (avf) {

            std::pair<SpatialSort, ai_real> &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;

    aiVector3D *pcNew = new aiVector3D[pMesh->mNumVertices];

    if (configMaxAngle >= AI_DEG_TO_RAD(175.f)) {

        // There is no angle limit. Thus all vertices with positions close

        // to each other will receive the same vertex normal. This allows us

        // to optimize the whole algorithm a little bit ...

        std::vector<bool> abHad(pMesh->mNumVertices, false);

        for (unsigned int i = 0; i < pMesh->mNumVertices; ++i) {

            if (abHad[i]) {

                continue;

            }

            // Get all vertices that share this one ...

            vertexFinder->FindPositions(pMesh->mVertices[i], posEpsilon, verticesFound);

            aiVector3D pcNor;

            for (unsigned int a = 0; a < verticesFound.size(); ++a) {

                const aiVector3D &v = pMesh->mNormals[verticesFound[a]];

                if (is_not_qnan(v.x)) pcNor += v;

            }

            pcNor.NormalizeSafe();

            // Write the smoothed normal back to all affected normals

            for (unsigned int a = 0; a < verticesFound.size(); ++a) {

                unsigned int vidx = verticesFound[a];

                pcNew[vidx] = pcNor;

                abHad[vidx] = true;

            }

        }

    }

    // Slower code path if a smooth angle is set. There are many ways to achieve

    // the effect, this one is the most straightforward one.

    else {

        const ai_real fLimit = std::cos(configMaxAngle);

        for (unsigned int i = 0; i < pMesh->mNumVertices; ++i) {

            // Get all vertices that share this one ...

            vertexFinder->FindPositions(pMesh->mVertices[i], posEpsilon, verticesFound);

            aiVector3D vr = pMesh->mNormals[i];

            aiVector3D pcNor;

            for (unsigned int a = 0; a < verticesFound.size(); ++a) {

                aiVector3D v = pMesh->mNormals[verticesFound[a]];

                // Check whether the angle between the two normals is not too large.

                // Skip the angle check on our own normal to avoid false negatives

                // (v*v is not guaranteed to be 1.0 for all unit vectors v)

                if (is_not_qnan(v.x) && (verticesFound[a] == i || (v * vr >= fLimit)))

                    pcNor += v;

            }

            pcNew[i] = pcNor.NormalizeSafe();

        }

    }

    delete[] pMesh->mNormals;

    pMesh->mNormals = pcNew;

    return true;

}