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/** @file  FBXMeshGeometry.cpp
 *  @brief Assimp::FBX::MeshGeometry implementation
 */

#ifndef ASSIMP_BUILD_NO_FBX_IMPORTER

#include <functional>

#include "FBXMeshGeometry.h"
#include "FBXDocument.h"
#include "FBXImporter.h"
#include "FBXImportSettings.h"
#include "FBXDocumentUtil.h"


namespace Assimp {
namespace FBX {

using namespace Util;

// ------------------------------------------------------------------------------------------------
Geometry::Geometry(uint64_t id, const Element& element, const std::string& name, const Document& doc)
    : Object(id, element,name)
    , skin()
{
    const std::vector<const Connection*>& conns = doc.GetConnectionsByDestinationSequenced(ID(),"Deformer");
    for(const Connection* con : conns) {
        const Skin* const sk = ProcessSimpleConnection<Skin>(*con, false, "Skin -> Geometry", element);
        if(sk) {
            skin = sk;
            break;
        }
    }
}


// ------------------------------------------------------------------------------------------------
Geometry::~Geometry()
{

}

const Skin* Geometry::DeformerSkin() const {
    return skin;
}


// ------------------------------------------------------------------------------------------------
MeshGeometry::MeshGeometry(uint64_t id, const Element& element, const std::string& name, const Document& doc)
: Geometry(id, element,name, doc)
{
    const Scope* sc = element.Compound();
    if (!sc) {
        DOMError("failed to read Geometry object (class: Mesh), no data scope found");
    }

    // must have Mesh elements:
    const Element& Vertices = GetRequiredElement(*sc,"Vertices",&element);
    const Element& PolygonVertexIndex = GetRequiredElement(*sc,"PolygonVertexIndex",&element);

    // optional Mesh elements:
    const ElementCollection& Layer = sc->GetCollection("Layer");

    std::vector<aiVector3D> tempVerts;
    ParseVectorDataArray(tempVerts,Vertices);

    if(tempVerts.empty()) {
        FBXImporter::LogWarn("encountered mesh with no vertices");
        return;
    }

    std::vector<int> tempFaces;
    ParseVectorDataArray(tempFaces,PolygonVertexIndex);

    if(tempFaces.empty()) {
        FBXImporter::LogWarn("encountered mesh with no faces");
        return;
    }

    m_vertices.reserve(tempFaces.size());
    m_faces.reserve(tempFaces.size() / 3);

    m_mapping_offsets.resize(tempVerts.size());
    m_mapping_counts.resize(tempVerts.size(),0);
    m_mappings.resize(tempFaces.size());

    const size_t vertex_count = tempVerts.size();

    // generate output vertices, computing an adjacency table to
    // preserve the mapping from fbx indices to *this* indexing.
    unsigned int count = 0;
    for(int index : tempFaces) {
        const int absi = index < 0 ? (-index - 1) : index;
        if(static_cast<size_t>(absi) >= vertex_count) {
            DOMError("polygon vertex index out of range",&PolygonVertexIndex);
        }

        m_vertices.push_back(tempVerts[absi]);
        ++count;

        ++m_mapping_counts[absi];

        if (index < 0) {
            m_faces.push_back(count);
            count = 0;
        }
    }

    unsigned int cursor = 0;
    for (size_t i = 0, e = tempVerts.size(); i < e; ++i) {
        m_mapping_offsets[i] = cursor;
        cursor += m_mapping_counts[i];

        m_mapping_counts[i] = 0;
    }

    cursor = 0;
    for(int index : tempFaces) {
        const int absi = index < 0 ? (-index - 1) : index;
        m_mappings[m_mapping_offsets[absi] + m_mapping_counts[absi]++] = cursor++;
    }

    // if settings.readAllLayers is true:
    //  * read all layers, try to load as many vertex channels as possible
    // if settings.readAllLayers is false:
    //  * read only the layer with index 0, but warn about any further layers
    for (ElementMap::const_iterator it = Layer.first; it != Layer.second; ++it) {
        const TokenList& tokens = (*it).second->Tokens();

        const char* err;
        const int index = ParseTokenAsInt(*tokens[0], err);
        if(err) {
            DOMError(err,&element);
        }

        if(doc.Settings().readAllLayers || index == 0) {
            const Scope& layer = GetRequiredScope(*(*it).second);
            ReadLayer(layer);
        }
        else {
            FBXImporter::LogWarn("ignoring additional geometry layers");
        }
    }
}

// ------------------------------------------------------------------------------------------------
MeshGeometry::~MeshGeometry()
{

}

// ------------------------------------------------------------------------------------------------
const std::vector<aiVector3D>& MeshGeometry::GetVertices() const {
    return m_vertices;
}

// ------------------------------------------------------------------------------------------------
const std::vector<aiVector3D>& MeshGeometry::GetNormals() const {
    return m_normals;
}

// ------------------------------------------------------------------------------------------------
const std::vector<aiVector3D>& MeshGeometry::GetTangents() const {
    return m_tangents;
}

// ------------------------------------------------------------------------------------------------
const std::vector<aiVector3D>& MeshGeometry::GetBinormals() const {
    return m_binormals;
}

// ------------------------------------------------------------------------------------------------
const std::vector<unsigned int>& MeshGeometry::GetFaceIndexCounts() const {
    return m_faces;
}

// ------------------------------------------------------------------------------------------------
const std::vector<aiVector2D>& MeshGeometry::GetTextureCoords( unsigned int index ) const {
    static const std::vector<aiVector2D> empty;
    return index >= AI_MAX_NUMBER_OF_TEXTURECOORDS ? empty : m_uvs[ index ];
}

std::string MeshGeometry::GetTextureCoordChannelName( unsigned int index ) const {
    return index >= AI_MAX_NUMBER_OF_TEXTURECOORDS ? "" : m_uvNames[ index ];
}

const std::vector<aiColor4D>& MeshGeometry::GetVertexColors( unsigned int index ) const {
    static const std::vector<aiColor4D> empty;
    return index >= AI_MAX_NUMBER_OF_COLOR_SETS ? empty : m_colors[ index ];
}

const MatIndexArray& MeshGeometry::GetMaterialIndices() const {
    return m_materials;
}

// ------------------------------------------------------------------------------------------------
const unsigned int* MeshGeometry::ToOutputVertexIndex( unsigned int in_index, unsigned int& count ) const {
    if ( in_index >= m_mapping_counts.size() ) {
        return NULL;
    }

    ai_assert( m_mapping_counts.size() == m_mapping_offsets.size() );
    count = m_mapping_counts[ in_index ];

    ai_assert( m_mapping_offsets[ in_index ] + count <= m_mappings.size() );

    return &m_mappings[ m_mapping_offsets[ in_index ] ];
}

// ------------------------------------------------------------------------------------------------
unsigned int MeshGeometry::FaceForVertexIndex( unsigned int in_index ) const {
    ai_assert( in_index < m_vertices.size() );

    // in the current conversion pattern this will only be needed if
    // weights are present, so no need to always pre-compute this table
    if ( m_facesVertexStartIndices.empty() ) {
        m_facesVertexStartIndices.resize( m_faces.size() + 1, 0 );

        std::partial_sum( m_faces.begin(), m_faces.end(), m_facesVertexStartIndices.begin() + 1 );
        m_facesVertexStartIndices.pop_back();
    }

    ai_assert( m_facesVertexStartIndices.size() == m_faces.size() );
    const std::vector<unsigned int>::iterator it = std::upper_bound(
        m_facesVertexStartIndices.begin(),
        m_facesVertexStartIndices.end(),
        in_index
        );

    return static_cast< unsigned int >( std::distance( m_facesVertexStartIndices.begin(), it - 1 ) );
}

// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadLayer(const Scope& layer)
{
    const ElementCollection& LayerElement = layer.GetCollection("LayerElement");
    for (ElementMap::const_iterator eit = LayerElement.first; eit != LayerElement.second; ++eit) {
        const Scope& elayer = GetRequiredScope(*(*eit).second);

        ReadLayerElement(elayer);
    }
}


// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadLayerElement(const Scope& layerElement)
{
    const Element& Type = GetRequiredElement(layerElement,"Type");
    const Element& TypedIndex = GetRequiredElement(layerElement,"TypedIndex");

    const std::string& type = ParseTokenAsString(GetRequiredToken(Type,0));
    const int typedIndex = ParseTokenAsInt(GetRequiredToken(TypedIndex,0));

    const Scope& top = GetRequiredScope(element);
    const ElementCollection candidates = top.GetCollection(type);

    for (ElementMap::const_iterator it = candidates.first; it != candidates.second; ++it) {
        const int index = ParseTokenAsInt(GetRequiredToken(*(*it).second,0));
        if(index == typedIndex) {
            ReadVertexData(type,typedIndex,GetRequiredScope(*(*it).second));
            return;
        }
    }

    FBXImporter::LogError(Formatter::format("failed to resolve vertex layer element: ")
        << type << ", index: " << typedIndex);
}


// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadVertexData(const std::string& type, int index, const Scope& source)
{
    const std::string& MappingInformationType = ParseTokenAsString(GetRequiredToken(
        GetRequiredElement(source,"MappingInformationType"),0)
    );

    const std::string& ReferenceInformationType = ParseTokenAsString(GetRequiredToken(
        GetRequiredElement(source,"ReferenceInformationType"),0)
    );

    if (type == "LayerElementUV") {
        if(index >= AI_MAX_NUMBER_OF_TEXTURECOORDS) {
            FBXImporter::LogError(Formatter::format("ignoring UV layer, maximum number of UV channels exceeded: ")
                << index << " (limit is " << AI_MAX_NUMBER_OF_TEXTURECOORDS << ")" );
            return;
        }

        const Element* Name = source["Name"];
        m_uvNames[index] = "";
        if(Name) {
            m_uvNames[index] = ParseTokenAsString(GetRequiredToken(*Name,0));
        }

        ReadVertexDataUV(m_uvs[index],source,
            MappingInformationType,
            ReferenceInformationType
        );
    }
    else if (type == "LayerElementMaterial") {
        if (m_materials.size() > 0) {
            FBXImporter::LogError("ignoring additional material layer");
            return;
        }

        std::vector<int> temp_materials;

        ReadVertexDataMaterials(temp_materials,source,
            MappingInformationType,
            ReferenceInformationType
        );

        // sometimes, there will be only negative entries. Drop the material
        // layer in such a case (I guess it means a default material should
        // be used). This is what the converter would do anyway, and it
        // avoids losing the material if there are more material layers
        // coming of which at least one contains actual data (did observe
        // that with one test file).
        const size_t count_neg = std::count_if(temp_materials.begin(),temp_materials.end(),[](int n) { return n < 0; });
        if(count_neg == temp_materials.size()) {
            FBXImporter::LogWarn("ignoring dummy material layer (all entries -1)");
            return;
        }

        std::swap(temp_materials, m_materials);
    }
    else if (type == "LayerElementNormal") {
        if (m_normals.size() > 0) {
            FBXImporter::LogError("ignoring additional normal layer");
            return;
        }

        ReadVertexDataNormals(m_normals,source,
            MappingInformationType,
            ReferenceInformationType
        );
    }
    else if (type == "LayerElementTangent") {
        if (m_tangents.size() > 0) {
            FBXImporter::LogError("ignoring additional tangent layer");
            return;
        }

        ReadVertexDataTangents(m_tangents,source,
            MappingInformationType,
            ReferenceInformationType
        );
    }
    else if (type == "LayerElementBinormal") {
        if (m_binormals.size() > 0) {
            FBXImporter::LogError("ignoring additional binormal layer");
            return;
        }

        ReadVertexDataBinormals(m_binormals,source,
            MappingInformationType,
            ReferenceInformationType
        );
    }
    else if (type == "LayerElementColor") {
        if(index >= AI_MAX_NUMBER_OF_COLOR_SETS) {
            FBXImporter::LogError(Formatter::format("ignoring vertex color layer, maximum number of color sets exceeded: ")
                << index << " (limit is " << AI_MAX_NUMBER_OF_COLOR_SETS << ")" );
            return;
        }

        ReadVertexDataColors(m_colors[index],source,
            MappingInformationType,
            ReferenceInformationType
        );
    }
}


// ------------------------------------------------------------------------------------------------
// Lengthy utility function to read and resolve a FBX vertex data array - that is, the
// output is in polygon vertex order. This logic is used for reading normals, UVs, colors,
// tangents ..
template <typename T>
void ResolveVertexDataArray(std::vector<T>& data_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType,
    const char* dataElementName,
    const char* indexDataElementName,
    size_t vertex_count,
    const std::vector<unsigned int>& mapping_counts,
    const std::vector<unsigned int>& mapping_offsets,
    const std::vector<unsigned int>& mappings)
{


    // handle permutations of Mapping and Reference type - it would be nice to
    // deal with this more elegantly and with less redundancy, but right
    // now it seems unavoidable.
    if (MappingInformationType == "ByVertice" && ReferenceInformationType == "Direct") {
		std::vector<T> tempData;
		ParseVectorDataArray(tempData, GetRequiredElement(source, dataElementName));

        data_out.resize(vertex_count);
		for (size_t i = 0, e = tempData.size(); i < e; ++i) {

            const unsigned int istart = mapping_offsets[i], iend = istart + mapping_counts[i];
            for (unsigned int j = istart; j < iend; ++j) {
				data_out[mappings[j]] = tempData[i];
            }
        }
    }
    else if (MappingInformationType == "ByVertice" && ReferenceInformationType == "IndexToDirect") {
		std::vector<T> tempData;
		ParseVectorDataArray(tempData, GetRequiredElement(source, dataElementName));

        data_out.resize(vertex_count);

        std::vector<int> uvIndices;
        ParseVectorDataArray(uvIndices,GetRequiredElement(source,indexDataElementName));

        for (size_t i = 0, e = uvIndices.size(); i < e; ++i) {

            const unsigned int istart = mapping_offsets[i], iend = istart + mapping_counts[i];
            for (unsigned int j = istart; j < iend; ++j) {
				if (static_cast<size_t>(uvIndices[i]) >= tempData.size()) {
                    DOMError("index out of range",&GetRequiredElement(source,indexDataElementName));
                }
				data_out[mappings[j]] = tempData[uvIndices[i]];
            }
        }
    }
    else if (MappingInformationType == "ByPolygonVertex" && ReferenceInformationType == "Direct") {
		std::vector<T> tempData;
		ParseVectorDataArray(tempData, GetRequiredElement(source, dataElementName));

		if (tempData.size() != vertex_count) {
            FBXImporter::LogError(Formatter::format("length of input data unexpected for ByPolygon mapping: ")
				<< tempData.size() << ", expected " << vertex_count
            );
            return;
        }

		data_out.swap(tempData);
    }
    else if (MappingInformationType == "ByPolygonVertex" && ReferenceInformationType == "IndexToDirect") {
		std::vector<T> tempData;
		ParseVectorDataArray(tempData, GetRequiredElement(source, dataElementName));

        data_out.resize(vertex_count);

        std::vector<int> uvIndices;
        ParseVectorDataArray(uvIndices,GetRequiredElement(source,indexDataElementName));

        if (uvIndices.size() != vertex_count) {
            FBXImporter::LogError("length of input data unexpected for ByPolygonVertex mapping");
            return;
        }

        unsigned int next = 0;
        for(int i : uvIndices) {
			if (static_cast<size_t>(i) >= tempData.size()) {
                DOMError("index out of range",&GetRequiredElement(source,indexDataElementName));
            }

			data_out[next++] = tempData[i];
        }
    }
    else {
        FBXImporter::LogError(Formatter::format("ignoring vertex data channel, access type not implemented: ")
            << MappingInformationType << "," << ReferenceInformationType);
    }
}

// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadVertexDataNormals(std::vector<aiVector3D>& normals_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType)
{
    ResolveVertexDataArray(normals_out,source,MappingInformationType,ReferenceInformationType,
        "Normals",
        "NormalsIndex",
        m_vertices.size(),
        m_mapping_counts,
        m_mapping_offsets,
        m_mappings);
}


// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadVertexDataUV(std::vector<aiVector2D>& uv_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType)
{
    ResolveVertexDataArray(uv_out,source,MappingInformationType,ReferenceInformationType,
        "UV",
        "UVIndex",
        m_vertices.size(),
        m_mapping_counts,
        m_mapping_offsets,
        m_mappings);
}


// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadVertexDataColors(std::vector<aiColor4D>& colors_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType)
{
    ResolveVertexDataArray(colors_out,source,MappingInformationType,ReferenceInformationType,
        "Colors",
        "ColorIndex",
        m_vertices.size(),
        m_mapping_counts,
        m_mapping_offsets,
        m_mappings);
}

// ------------------------------------------------------------------------------------------------
static const std::string TangentIndexToken = "TangentIndex";
static const std::string TangentsIndexToken = "TangentsIndex";

void MeshGeometry::ReadVertexDataTangents(std::vector<aiVector3D>& tangents_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType)
{
    const char * str = source.Elements().count( "Tangents" ) > 0 ? "Tangents" : "Tangent";
    const char * strIdx = source.Elements().count( "Tangents" ) > 0 ? TangentsIndexToken.c_str() : TangentIndexToken.c_str();
    ResolveVertexDataArray(tangents_out,source,MappingInformationType,ReferenceInformationType,
        str,
        strIdx,
        m_vertices.size(),
        m_mapping_counts,
        m_mapping_offsets,
        m_mappings);
}

// ------------------------------------------------------------------------------------------------
static const std::string BinormalIndexToken = "BinormalIndex";
static const std::string BinormalsIndexToken = "BinormalsIndex";

void MeshGeometry::ReadVertexDataBinormals(std::vector<aiVector3D>& binormals_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType)
{
    const char * str = source.Elements().count( "Binormals" ) > 0 ? "Binormals" : "Binormal";
    const char * strIdx = source.Elements().count( "Binormals" ) > 0 ? BinormalsIndexToken.c_str() : BinormalIndexToken.c_str();
    ResolveVertexDataArray(binormals_out,source,MappingInformationType,ReferenceInformationType,
        str,
        strIdx,
        m_vertices.size(),
        m_mapping_counts,
        m_mapping_offsets,
        m_mappings);
}


// ------------------------------------------------------------------------------------------------
void MeshGeometry::ReadVertexDataMaterials(std::vector<int>& materials_out, const Scope& source,
    const std::string& MappingInformationType,
    const std::string& ReferenceInformationType)
{
    const size_t face_count = m_faces.size();
    ai_assert(face_count);

    // materials are handled separately. First of all, they are assigned per-face
    // and not per polyvert. Secondly, ReferenceInformationType=IndexToDirect
    // has a slightly different meaning for materials.
    ParseVectorDataArray(materials_out,GetRequiredElement(source,"Materials"));

    if (MappingInformationType == "AllSame") {
        // easy - same material for all faces
        if (materials_out.empty()) {
            FBXImporter::LogError(Formatter::format("expected material index, ignoring"));
            return;
        }
        else if (materials_out.size() > 1) {
            FBXImporter::LogWarn(Formatter::format("expected only a single material index, ignoring all except the first one"));
            materials_out.clear();
        }

        m_materials.assign(m_vertices.size(),materials_out[0]);
    }
    else if (MappingInformationType == "ByPolygon" && ReferenceInformationType == "IndexToDirect") {
        m_materials.resize(face_count);

        if(materials_out.size() != face_count) {
            FBXImporter::LogError(Formatter::format("length of input data unexpected for ByPolygon mapping: ")
                << materials_out.size() << ", expected " << face_count
            );
            return;
        }
    }
    else {
        FBXImporter::LogError(Formatter::format("ignoring material assignments, access type not implemented: ")
            << MappingInformationType << "," << ReferenceInformationType);
    }
}

} // !FBX
} // !Assimp

#endif