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/** @file  BlenderModifier.cpp

 *  @brief Implementation of some blender modifiers (i.e subdivision, mirror).

 */

#ifndef ASSIMP_BUILD_NO_BLEND_IMPORTER

#include "BlenderModifier.h"

#include <assimp/SceneCombiner.h>

#include <assimp/Subdivision.h>

#include <assimp/scene.h>

#include <memory>

#include <functional>

using namespace Assimp;

using namespace Assimp::Blender;

template <typename T>

BlenderModifier *god() {

    return new T();

}

Unexecuted instantiation: Assimp::Blender::BlenderModifier* god<Assimp::Blender::BlenderModifier_Mirror>()

Unexecuted instantiation: Assimp::Blender::BlenderModifier* god<Assimp::Blender::BlenderModifier_Subdivision>()

// add all available modifiers here

typedef BlenderModifier *(*fpCreateModifier)();

static const fpCreateModifier creators[] = {

    &god<BlenderModifier_Mirror>,

    &god<BlenderModifier_Subdivision>,

    nullptr // sentinel

};

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

void BlenderModifierShowcase::ApplyModifiers(aiNode &out, ConversionData &conv_data, const Scene &in, const Object &orig_object) {

    size_t cnt = 0u, ful = 0u;

    // NOTE: this cast is potentially unsafe by design, so we need to perform type checks before

    // we're allowed to dereference the pointers without risking to crash. We might still be

    // invoking UB btw - we're assuming that the ModifierData member of the respective modifier

    // structures is at offset sizeof(vftable) with no padding.

    const SharedModifierData *cur = static_cast<const SharedModifierData *>(orig_object.modifiers.first.get());

    for (; cur; cur = static_cast<const SharedModifierData *>(cur->modifier.next.get()), ++ful) {

        ai_assert(cur->dna_type);

        const Structure *s = conv_data.db.dna.Get(cur->dna_type);

        if (!s) {

            ASSIMP_LOG_WARN("BlendModifier: could not resolve DNA name: ", cur->dna_type);

            continue;

        }

        // this is a common trait of all XXXMirrorData structures in BlenderDNA

        const Field *f = s->Get("modifier");

        if (!f || f->offset != 0) {

            ASSIMP_LOG_WARN("BlendModifier: expected a `modifier` member at offset 0");

            continue;

        }

        s = conv_data.db.dna.Get(f->type);

        if (!s || s->name != "ModifierData") {

            ASSIMP_LOG_WARN("BlendModifier: expected a ModifierData structure as first member");

            continue;

        }

        // now, we can be sure that we should be fine to dereference *cur* as

        // ModifierData (with the above note).

        const ModifierData &dat = cur->modifier;

        const fpCreateModifier *curgod = creators;

        std::vector<BlenderModifier *>::iterator curmod = cached_modifiers->begin(), endmod = cached_modifiers->end();

        for (; *curgod; ++curgod, ++curmod) { // allocate modifiers on the fly

            if (curmod == endmod) {

                cached_modifiers->push_back((*curgod)());

                endmod = cached_modifiers->end();

                curmod = endmod - 1;

            }

            BlenderModifier *const modifier = *curmod;

            if (modifier->IsActive(dat)) {

                modifier->DoIt(out, conv_data, *static_cast<const ElemBase *>(cur), in, orig_object);

                cnt++;

                curgod = nullptr;

                break;

            }

        }

        if (curgod) {

            ASSIMP_LOG_WARN("Couldn't find a handler for modifier: ", dat.name);

        }

    }

    // Even though we managed to resolve some or all of the modifiers on this

    // object, we still can't say whether our modifier implementations were

    // able to fully do their job.

    if (ful) {

        ASSIMP_LOG_DEBUG("BlendModifier: found handlers for ", cnt, " of ", ful, " modifiers on `", orig_object.id.name,

                "`, check log messages above for errors");

    }

}

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

bool BlenderModifier_Mirror ::IsActive(const ModifierData &modin) {

    return modin.type == ModifierData::eModifierType_Mirror;

}

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

void BlenderModifier_Mirror ::DoIt(aiNode &out, ConversionData &conv_data, const ElemBase &orig_modifier,

        const Scene & /*in*/,

        const Object &orig_object) {

    // hijacking the ABI, see the big note in BlenderModifierShowcase::ApplyModifiers()

    const MirrorModifierData &mir = static_cast<const MirrorModifierData &>(orig_modifier);

    ai_assert(mir.modifier.type == ModifierData::eModifierType_Mirror);

    std::shared_ptr<Object> mirror_ob = mir.mirror_ob.lock();

    conv_data.meshes->reserve(conv_data.meshes->size() + out.mNumMeshes);

    // XXX not entirely correct, mirroring on two axes results in 4 distinct objects in blender ...

    // take all input meshes and clone them

    for (unsigned int i = 0; i < out.mNumMeshes; ++i) {

        aiMesh *mesh;

        SceneCombiner::Copy(&mesh, conv_data.meshes[out.mMeshes[i]]);

        const float xs = mir.flag & MirrorModifierData::Flags_AXIS_X ? -1.f : 1.f;

        const float ys = mir.flag & MirrorModifierData::Flags_AXIS_Y ? -1.f : 1.f;

        const float zs = mir.flag & MirrorModifierData::Flags_AXIS_Z ? -1.f : 1.f;

        if (mirror_ob) {

            const aiVector3D center(mirror_ob->obmat[3][0], mirror_ob->obmat[3][1], mirror_ob->obmat[3][2]);

            for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {

                aiVector3D &v = mesh->mVertices[j];

                v.x = center.x + xs * (center.x - v.x);

                v.y = center.y + ys * (center.y - v.y);

                v.z = center.z + zs * (center.z - v.z);

            }

        } else {

            for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {

                aiVector3D &v = mesh->mVertices[j];

                v.x *= xs;

                v.y *= ys;

                v.z *= zs;

            }

        }

        if (mesh->mNormals) {

            for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {

                aiVector3D &v = mesh->mNormals[j];

                v.x *= xs;

                v.y *= ys;

                v.z *= zs;

            }

        }

        if (mesh->mTangents) {

            for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {

                aiVector3D &v = mesh->mTangents[j];

                v.x *= xs;

                v.y *= ys;

                v.z *= zs;

            }

        }

        if (mesh->mBitangents) {

            for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {

                aiVector3D &v = mesh->mBitangents[j];

                v.x *= xs;

                v.y *= ys;

                v.z *= zs;

            }

        }

        const float us = mir.flag & MirrorModifierData::Flags_MIRROR_U ? -1.f : 1.f;

        const float vs = mir.flag & MirrorModifierData::Flags_MIRROR_V ? -1.f : 1.f;

        for (unsigned int n = 0; mesh->HasTextureCoords(n); ++n) {

            for (unsigned int j = 0; j < mesh->mNumVertices; ++j) {

                aiVector3D &v = mesh->mTextureCoords[n][j];

                v.x *= us;

                v.y *= vs;

            }

        }

        // Only reverse the winding order if an odd number of axes were mirrored.

        if (xs * ys * zs < 0) {

            for (unsigned int j = 0; j < mesh->mNumFaces; ++j) {

                aiFace &face = mesh->mFaces[j];

                for (unsigned int fi = 0; fi < face.mNumIndices / 2; ++fi)

                    std::swap(face.mIndices[fi], face.mIndices[face.mNumIndices - 1 - fi]);

            }

        }

        conv_data.meshes->push_back(mesh);

    }

    unsigned int *nind = new unsigned int[out.mNumMeshes * 2];

    std::copy(out.mMeshes, out.mMeshes + out.mNumMeshes, nind);

    std::transform(out.mMeshes, out.mMeshes + out.mNumMeshes, nind + out.mNumMeshes,

            [&out](unsigned int n) { return out.mNumMeshes + n; });

    delete[] out.mMeshes;

    out.mMeshes = nind;

    out.mNumMeshes *= 2;

    ASSIMP_LOG_INFO("BlendModifier: Applied the `Mirror` modifier to `",

            orig_object.id.name, "`");

}

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

bool BlenderModifier_Subdivision ::IsActive(const ModifierData &modin) {

    return modin.type == ModifierData::eModifierType_Subsurf;

}

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

void BlenderModifier_Subdivision ::DoIt(aiNode &out, ConversionData &conv_data, const ElemBase &orig_modifier,

        const Scene & /*in*/,

        const Object &orig_object) {

    // hijacking the ABI, see the big note in BlenderModifierShowcase::ApplyModifiers()

    const SubsurfModifierData &mir = static_cast<const SubsurfModifierData &>(orig_modifier);

    ai_assert(mir.modifier.type == ModifierData::eModifierType_Subsurf);

    Subdivider::Algorithm algo;

    switch (mir.subdivType) {

    case SubsurfModifierData::TYPE_CatmullClarke:

        algo = Subdivider::CATMULL_CLARKE;

        break;

    case SubsurfModifierData::TYPE_Simple:

        ASSIMP_LOG_WARN("BlendModifier: The `SIMPLE` subdivision algorithm is not currently implemented, using Catmull-Clarke");

        algo = Subdivider::CATMULL_CLARKE;

        break;

    default:

        ASSIMP_LOG_WARN("BlendModifier: Unrecognized subdivision algorithm: ", mir.subdivType);

        return;

    };

    std::unique_ptr<Subdivider> subd(Subdivider::Create(algo));

    ai_assert(subd);

    if (conv_data.meshes->empty()) {

        return;

    }

    const size_t meshIndex = conv_data.meshes->size() - out.mNumMeshes;

    if (meshIndex >= conv_data.meshes->size()) {

        ASSIMP_LOG_ERROR("Invalid index detected.");

        return;

    }

    aiMesh **const meshes = &conv_data.meshes[conv_data.meshes->size() - out.mNumMeshes];

    std::unique_ptr<aiMesh *[]> tempmeshes(new aiMesh *[out.mNumMeshes]());

    subd->Subdivide(meshes, out.mNumMeshes, tempmeshes.get(), std::max(mir.renderLevels, mir.levels), true);

    std::copy(tempmeshes.get(), tempmeshes.get() + out.mNumMeshes, meshes);

    ASSIMP_LOG_INFO("BlendModifier: Applied the `Subdivision` modifier to `",

            orig_object.id.name, "`");

}

#endif // ASSIMP_BUILD_NO_BLEND_IMPORTER