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/** @file Implementation of the material oart of the LWO importer class */

#ifndef ASSIMP_BUILD_NO_LWO_IMPORTER

// internal headers
#include "LWOLoader.h"
#include <assimp/ByteSwapper.h>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
template <class T>
T lerp(const T &one, const T &two, float val) {
    return one + (two - one) * val;
}

// ------------------------------------------------------------------------------------------------
// Convert a lightwave mapping mode to our's
inline aiTextureMapMode GetMapMode(LWO::Texture::Wrap in) {
    switch (in) {
        case LWO::Texture::REPEAT:
            return aiTextureMapMode_Wrap;

        case LWO::Texture::MIRROR:
            return aiTextureMapMode_Mirror;

        case LWO::Texture::RESET:
            ASSIMP_LOG_WARN("LWO2: Unsupported texture map mode: RESET");

            // fall though here
        case LWO::Texture::EDGE:
            return aiTextureMapMode_Clamp;
    }
    return (aiTextureMapMode)0;
}

// ------------------------------------------------------------------------------------------------
bool LWOImporter::HandleTextures(aiMaterial *pcMat, const TextureList &in, aiTextureType type) {
    ai_assert(nullptr != pcMat);

    unsigned int cur = 0, temp = 0;
    aiString s;
    bool ret = false;

    for (const auto &texture : in) {
        if (!texture.enabled || !texture.bCanUse)
            continue;
        ret = true;

        // Convert lightwave's mapping modes to ours. We let them
        // as they are, the GenUVcoords step will compute UV
        // channels if they're not there.

        aiTextureMapping mapping = aiTextureMapping_OTHER;
        switch (texture.mapMode) {
            case LWO::Texture::Planar:
                mapping = aiTextureMapping_PLANE;
                break;
            case LWO::Texture::Cylindrical:
                mapping = aiTextureMapping_CYLINDER;
                break;
            case LWO::Texture::Spherical:
                mapping = aiTextureMapping_SPHERE;
                break;
            case LWO::Texture::Cubic:
                mapping = aiTextureMapping_BOX;
                break;
            case LWO::Texture::FrontProjection:
                ASSIMP_LOG_ERROR("LWO2: Unsupported texture mapping: FrontProjection");
                mapping = aiTextureMapping_OTHER;
                break;
            case LWO::Texture::UV: {
                if (UINT_MAX == texture.mRealUVIndex) {
                    // We have no UV index for this texture, so we can't display it
                    continue;
                }

                // add the UV source index
                temp = texture.mRealUVIndex;
                pcMat->AddProperty<int>((int *)&temp, 1, AI_MATKEY_UVWSRC(type, cur));

                mapping = aiTextureMapping_UV;
            } break;
            default:
                ai_assert(false);
        };

        if (mapping != aiTextureMapping_UV) {
            // Setup the main axis
            aiVector3D v;
            switch (texture.majorAxis) {
                case Texture::AXIS_X:
                    v = aiVector3D(1.0, 0.0, 0.0);
                    break;
                case Texture::AXIS_Y:
                    v = aiVector3D(0.0, 1.0, 0.0);
                    break;
                default: // case Texture::AXIS_Z:
                    v = aiVector3D(0.0, 0.0, 1.0);
                    break;
            }

            pcMat->AddProperty(&v, 1, AI_MATKEY_TEXMAP_AXIS(type, cur));

            // Setup UV scalings for cylindric and spherical projections
            if (mapping == aiTextureMapping_CYLINDER || mapping == aiTextureMapping_SPHERE) {
                aiUVTransform trafo;
                trafo.mScaling.x = texture.wrapAmountW;
                trafo.mScaling.y = texture.wrapAmountH;

                static_assert(sizeof(aiUVTransform) / sizeof(ai_real) == 5, "sizeof(aiUVTransform)/sizeof(ai_real) == 5");
                pcMat->AddProperty(&trafo, 1, AI_MATKEY_UVTRANSFORM(type, cur));
            }
            ASSIMP_LOG_VERBOSE_DEBUG("LWO2: Setting up non-UV mapping");
        }

        // The older LWOB format does not use indirect references to clips.
        // The file name of a texture is directly specified in the tex chunk.
        if (mIsLWO2) {
            // find the corresponding clip (take the last one if multiple
            // share the same index)
            ClipList::iterator end = mClips.end(), candidate = end;
            temp = texture.mClipIdx;
            for (ClipList::iterator clip = mClips.begin(); clip != end; ++clip) {
                if ((*clip).idx == temp) {
                    candidate = clip;
                }
            }
            if (candidate == end) {
                ASSIMP_LOG_ERROR("LWO2: Clip index is out of bounds");
                temp = 0;

                // fixme: apparently some LWO files shipping with Doom3 don't
                // have clips at all ... check whether that's true or whether
                // it's a bug in the loader.

                s.Set("$texture.png");

                //continue;
            } else {
                if (Clip::UNSUPPORTED == (*candidate).type) {
                    ASSIMP_LOG_ERROR("LWO2: Clip type is not supported");
                    continue;
                }
                AdjustTexturePath((*candidate).path);
                s.Set((*candidate).path);

                // Additional image settings
                int flags = 0;
                if ((*candidate).negate) {
                    flags |= aiTextureFlags_Invert;
                }
                pcMat->AddProperty(&flags, 1, AI_MATKEY_TEXFLAGS(type, cur));
            }
        } else {
            std::string ss = texture.mFileName;
            if (!ss.length()) {
                ASSIMP_LOG_WARN("LWOB: Empty file name");
                continue;
            }
            AdjustTexturePath(ss);
            s.Set(ss);
        }
        pcMat->AddProperty(&s, AI_MATKEY_TEXTURE(type, cur));

        // add the blend factor
        pcMat->AddProperty<float>(&texture.mStrength, 1, AI_MATKEY_TEXBLEND(type, cur));

        // add the blend operation
        switch (texture.blendType) {
            case LWO::Texture::Normal:
            case LWO::Texture::Multiply:
                temp = (unsigned int)aiTextureOp_Multiply;
                break;

            case LWO::Texture::Subtractive:
            case LWO::Texture::Difference:
                temp = (unsigned int)aiTextureOp_Subtract;
                break;

            case LWO::Texture::Divide:
                temp = (unsigned int)aiTextureOp_Divide;
                break;

            case LWO::Texture::Additive:
                temp = (unsigned int)aiTextureOp_Add;
                break;

            default:
                temp = (unsigned int)aiTextureOp_Multiply;
                ASSIMP_LOG_WARN("LWO2: Unsupported texture blend mode: alpha or displacement");
        }
        // Setup texture operation
        pcMat->AddProperty<int>((int *)&temp, 1, AI_MATKEY_TEXOP(type, cur));

        // setup the mapping mode
        int mapping_ = static_cast<int>(mapping);
        pcMat->AddProperty<int>(&mapping_, 1, AI_MATKEY_MAPPING(type, cur));

        // add the u-wrapping
        temp = (unsigned int)GetMapMode(texture.wrapModeWidth);
        pcMat->AddProperty<int>((int *)&temp, 1, AI_MATKEY_MAPPINGMODE_U(type, cur));

        // add the v-wrapping
        temp = (unsigned int)GetMapMode(texture.wrapModeHeight);
        pcMat->AddProperty<int>((int *)&temp, 1, AI_MATKEY_MAPPINGMODE_V(type, cur));

        ++cur;
    }
    return ret;
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::ConvertMaterial(const LWO::Surface &surf, aiMaterial *pcMat) {
    // copy the name of the surface
    aiString st;
    st.Set(surf.mName);
    pcMat->AddProperty(&st, AI_MATKEY_NAME);

    const int i = surf.bDoubleSided ? 1 : 0;
    pcMat->AddProperty(&i, 1, AI_MATKEY_TWOSIDED);

    // add the refraction index and the bump intensity
    pcMat->AddProperty(&surf.mIOR, 1, AI_MATKEY_REFRACTI);
    pcMat->AddProperty(&surf.mBumpIntensity, 1, AI_MATKEY_BUMPSCALING);

    aiShadingMode m;
    if (surf.mSpecularValue && surf.mGlossiness) {
        float fGloss;
        if (mIsLWO2) {
            fGloss = std::pow(surf.mGlossiness * ai_real(10.0) + ai_real(2.0), ai_real(2.0));
        } else {
            if (16.0 >= surf.mGlossiness)
                fGloss = 6.0;
            else if (64.0 >= surf.mGlossiness)
                fGloss = 20.0;
            else if (256.0 >= surf.mGlossiness)
                fGloss = 50.0;
            else
                fGloss = 80.0;
        }

        pcMat->AddProperty(&surf.mSpecularValue, 1, AI_MATKEY_SHININESS_STRENGTH);
        pcMat->AddProperty(&fGloss, 1, AI_MATKEY_SHININESS);
        m = aiShadingMode_Phong;
    } else
        m = aiShadingMode_Gouraud;

    // specular color
    aiColor3D clr = lerp(aiColor3D(1.0, 1.0, 1.0), surf.mColor, surf.mColorHighlights);
    pcMat->AddProperty(&clr, 1, AI_MATKEY_COLOR_SPECULAR);
    pcMat->AddProperty(&surf.mSpecularValue, 1, AI_MATKEY_SHININESS_STRENGTH);

    // emissive color
    // luminosity is not really the same but it affects the surface in a similar way. Some scaling looks good.
    clr.g = clr.b = clr.r = surf.mLuminosity * ai_real(0.8);
    pcMat->AddProperty<aiColor3D>(&clr, 1, AI_MATKEY_COLOR_EMISSIVE);

    // opacity ... either additive or default-blended, please
    if (0.0 != surf.mAdditiveTransparency) {
        const int add = aiBlendMode_Additive;
        pcMat->AddProperty(&surf.mAdditiveTransparency, 1, AI_MATKEY_OPACITY);
        pcMat->AddProperty(&add, 1, AI_MATKEY_BLEND_FUNC);
    } else if (10e10f != surf.mTransparency) {
        const int def = aiBlendMode_Default;
        const float f = 1.0f - surf.mTransparency;
        pcMat->AddProperty(&f, 1, AI_MATKEY_OPACITY);
        pcMat->AddProperty(&def, 1, AI_MATKEY_BLEND_FUNC);
    }

    // ADD TEXTURES to the material
    // TODO: find out how we can handle COLOR textures correctly...
    bool b = HandleTextures(pcMat, surf.mColorTextures, aiTextureType_DIFFUSE);
    b = (b || HandleTextures(pcMat, surf.mDiffuseTextures, aiTextureType_DIFFUSE));
    HandleTextures(pcMat, surf.mSpecularTextures, aiTextureType_SPECULAR);
    HandleTextures(pcMat, surf.mGlossinessTextures, aiTextureType_SHININESS);
    HandleTextures(pcMat, surf.mBumpTextures, aiTextureType_HEIGHT);
    HandleTextures(pcMat, surf.mOpacityTextures, aiTextureType_OPACITY);
    HandleTextures(pcMat, surf.mReflectionTextures, aiTextureType_REFLECTION);

    // Now we need to know which shader to use .. iterate through the shader list of
    // the surface and  search for a name which we know ...
    for (const auto &shader : surf.mShaders) {
        if (shader.functionName == "LW_SuperCelShader" || shader.functionName == "AH_CelShader") {
            ASSIMP_LOG_INFO("LWO2: Mapping LW_SuperCelShader/AH_CelShader to aiShadingMode_Toon");

            m = aiShadingMode_Toon;
            break;
        } else if (shader.functionName == "LW_RealFresnel" || shader.functionName == "LW_FastFresnel") {
            ASSIMP_LOG_INFO("LWO2: Mapping LW_RealFresnel/LW_FastFresnel to aiShadingMode_Fresnel");

            m = aiShadingMode_Fresnel;
            break;
        } else {
            ASSIMP_LOG_WARN("LWO2: Unknown surface shader: ", shader.functionName);
        }
    }
    if (surf.mMaximumSmoothAngle <= 0.0)
        m = aiShadingMode_Flat;
    int m_ = static_cast<int>(m);
    pcMat->AddProperty(&m_, 1, AI_MATKEY_SHADING_MODEL);

    // (the diffuse value is just a scaling factor)
    // If a diffuse texture is set, we set this value to 1.0
    clr = (b && false ? aiColor3D(1.0, 1.0, 1.0) : surf.mColor);
    clr.r *= surf.mDiffuseValue;
    clr.g *= surf.mDiffuseValue;
    clr.b *= surf.mDiffuseValue;
    pcMat->AddProperty<aiColor3D>(&clr, 1, AI_MATKEY_COLOR_DIFFUSE);
}

// ------------------------------------------------------------------------------------------------
char LWOImporter::FindUVChannels(LWO::TextureList &list,
        LWO::Layer & /*layer*/, LWO::UVChannel &uv, unsigned int next) {
    char ret = 0;
    for (auto &texture : list) {

        // Ignore textures with non-UV mappings for the moment.
        if (!texture.enabled || !texture.bCanUse || texture.mapMode != LWO::Texture::UV) {
            continue;
        }

        if (texture.mUVChannelIndex == uv.name) {
            ret = 1;

            // got it.
            if (texture.mRealUVIndex == UINT_MAX || texture.mRealUVIndex == next) {
                texture.mRealUVIndex = next;
            } else {
                // channel mismatch. need to duplicate the material.
                ASSIMP_LOG_WARN("LWO: Channel mismatch, would need to duplicate surface [design bug]");

                // TODO
            }
        }
    }
    return ret;
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::FindUVChannels(LWO::Surface &surf,
        LWO::SortedRep &sorted, LWO::Layer &layer,
        unsigned int out[AI_MAX_NUMBER_OF_TEXTURECOORDS]) {
    unsigned int next = 0, extra = 0, num_extra = 0;

    // Check whether we have an UV entry != 0 for one of the faces in 'sorted'
    for (unsigned int i = 0; i < layer.mUVChannels.size(); ++i) {
        LWO::UVChannel &uv = layer.mUVChannels[i];

        for (LWO::SortedRep::const_iterator it = sorted.begin(); it != sorted.end(); ++it) {

            LWO::Face &face = layer.mFaces[*it];

            for (unsigned int n = 0; n < face.mNumIndices; ++n) {
                unsigned int idx = face.mIndices[n];

                if (uv.abAssigned[idx] && ((aiVector2D *)&uv.rawData[0])[idx] != aiVector2D()) {

                    if (extra >= AI_MAX_NUMBER_OF_TEXTURECOORDS) {

                        ASSIMP_LOG_ERROR("LWO: Maximum number of UV channels for "
                                         "this mesh reached. Skipping channel \'" +
                                         uv.name + "\'");

                    } else {
                        // Search through all textures assigned to 'surf' and look for this UV channel
                        char had = 0;
                        had |= FindUVChannels(surf.mColorTextures, layer, uv, next);
                        had |= FindUVChannels(surf.mDiffuseTextures, layer, uv, next);
                        had |= FindUVChannels(surf.mSpecularTextures, layer, uv, next);
                        had |= FindUVChannels(surf.mGlossinessTextures, layer, uv, next);
                        had |= FindUVChannels(surf.mOpacityTextures, layer, uv, next);
                        had |= FindUVChannels(surf.mBumpTextures, layer, uv, next);
                        had |= FindUVChannels(surf.mReflectionTextures, layer, uv, next);

                        // We have a texture referencing this UV channel so we have to take special care
                        // and are willing to drop unreferenced channels in favour of it.
                        if (had != 0) {
                            if (num_extra) {

                                for (unsigned int a = next; a < std::min(extra, AI_MAX_NUMBER_OF_TEXTURECOORDS - 1u); ++a) {
                                    out[a + 1] = out[a];
                                }
                            }
                            ++extra;
                            out[next++] = i;
                        }
                        // Bah ... seems not to be used at all. Push to end if enough space is available.
                        else {
                            out[extra++] = i;
                            ++num_extra;
                        }
                    }
                    it = sorted.end() - 1;
                    break;
                }
            }
        }
    }
    if (extra < AI_MAX_NUMBER_OF_TEXTURECOORDS) {
        out[extra] = UINT_MAX;
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::FindVCChannels(const LWO::Surface &surf, LWO::SortedRep &sorted, const LWO::Layer &layer,
        unsigned int out[AI_MAX_NUMBER_OF_COLOR_SETS]) {
    unsigned int next = 0;

    // Check whether we have an vc entry != 0 for one of the faces in 'sorted'
    for (unsigned int i = 0; i < layer.mVColorChannels.size(); ++i) {
        const LWO::VColorChannel &vc = layer.mVColorChannels[i];

        if (surf.mVCMap == vc.name) {
            // The vertex color map is explicitly requested by the surface so we need to take special care of it
            for (unsigned int a = 0; a < std::min(next, AI_MAX_NUMBER_OF_COLOR_SETS - 1u); ++a) {
                out[a + 1] = out[a];
            }
            out[0] = i;
            ++next;
        } else {

            for (LWO::SortedRep::iterator it = sorted.begin(); it != sorted.end(); ++it) {
                const LWO::Face &face = layer.mFaces[*it];

                for (unsigned int n = 0; n < face.mNumIndices; ++n) {
                    unsigned int idx = face.mIndices[n];

                    if (vc.abAssigned[idx] && ((aiColor4D *)&vc.rawData[0])[idx] != aiColor4D(0.0, 0.0, 0.0, 1.0)) {
                        if (next >= AI_MAX_NUMBER_OF_COLOR_SETS) {

                            ASSIMP_LOG_ERROR("LWO: Maximum number of vertex color channels for "
                                             "this mesh reached. Skipping channel \'" +
                                             vc.name + "\'");

                        } else {
                            out[next++] = i;
                        }
                        it = sorted.end() - 1;
                        break;
                    }
                }
            }
        }
    }
    if (next != AI_MAX_NUMBER_OF_COLOR_SETS) {
        out[next] = UINT_MAX;
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2ImageMap(unsigned int size, LWO::Texture &tex) {
    LE_NCONST uint8_t *const end = mFileBuffer + size;
    while (true) {
        if (mFileBuffer + 6 >= end) break;
        LE_NCONST IFF::SubChunkHeader head = IFF::LoadSubChunk(mFileBuffer);

        if (mFileBuffer + head.length > end)
            throw DeadlyImportError("LWO2: Invalid SURF.BLOCK chunk length");

        uint8_t *const next = mFileBuffer + head.length;
        switch (head.type) {
            case AI_LWO_PROJ:
                tex.mapMode = (Texture::MappingMode)GetU2();
                break;
            case AI_LWO_WRAP:
                tex.wrapModeWidth = (Texture::Wrap)GetU2();
                tex.wrapModeHeight = (Texture::Wrap)GetU2();
                break;
            case AI_LWO_AXIS:
                tex.majorAxis = (Texture::Axes)GetU2();
                break;
            case AI_LWO_IMAG:
                tex.mClipIdx = GetU2();
                break;
            case AI_LWO_VMAP:
                GetS0(tex.mUVChannelIndex, head.length);
                break;
            case AI_LWO_WRPH:
                tex.wrapAmountH = GetF4();
                break;
            case AI_LWO_WRPW:
                tex.wrapAmountW = GetF4();
                break;
        }
        mFileBuffer = next;
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2Procedural(unsigned int /*size*/, LWO::Texture &tex) {
    // --- not supported at the moment
    ASSIMP_LOG_ERROR("LWO2: Found procedural texture, this is not supported");
    tex.bCanUse = false;
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2Gradient(unsigned int /*size*/, LWO::Texture &tex) {
    // --- not supported at the moment
    ASSIMP_LOG_ERROR("LWO2: Found gradient texture, this is not supported");
    tex.bCanUse = false;
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2TextureHeader(unsigned int size, LWO::Texture &tex) {
    LE_NCONST uint8_t *const end = mFileBuffer + size;

    // get the ordinal string
    GetS0(tex.ordinal, size);

    // we could crash later if this is an empty string ...
    if (!tex.ordinal.length()) {
        ASSIMP_LOG_ERROR("LWO2: Ill-formed SURF.BLOK ordinal string");
        tex.ordinal = "\x00";
    }
    while (true) {
        if (mFileBuffer + 6 >= end) break;
        const IFF::SubChunkHeader head = IFF::LoadSubChunk(mFileBuffer);

        if (mFileBuffer + head.length > end)
            throw DeadlyImportError("LWO2: Invalid texture header chunk length");

        uint8_t *const next = mFileBuffer + head.length;
        switch (head.type) {
            case AI_LWO_CHAN:
                tex.type = GetU4();
                break;
            case AI_LWO_ENAB:
                tex.enabled = GetU2() ? true : false;
                break;
            case AI_LWO_OPAC:
                tex.blendType = (Texture::BlendType)GetU2();
                tex.mStrength = GetF4();
                break;
        }
        mFileBuffer = next;
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2TextureBlock(LE_NCONST IFF::SubChunkHeader *head, unsigned int size) {
    ai_assert(!mSurfaces->empty());
    LWO::Surface &surf = mSurfaces->back();
    LWO::Texture tex;

    // load the texture header
    LoadLWO2TextureHeader(head->length, tex);
    size -= head->length + 6;

    // now get the exact type of the texture
    switch (head->type) {
        case AI_LWO_PROC:
            LoadLWO2Procedural(size, tex);
            break;
        case AI_LWO_GRAD:
            LoadLWO2Gradient(size, tex);
            break;
        case AI_LWO_IMAP:
            LoadLWO2ImageMap(size, tex);
    }

    // get the destination channel
    TextureList *listRef = nullptr;
    switch (tex.type) {
        case AI_LWO_COLR:
            listRef = &surf.mColorTextures;
            break;
        case AI_LWO_DIFF:
            listRef = &surf.mDiffuseTextures;
            break;
        case AI_LWO_SPEC:
            listRef = &surf.mSpecularTextures;
            break;
        case AI_LWO_GLOS:
            listRef = &surf.mGlossinessTextures;
            break;
        case AI_LWO_BUMP:
            listRef = &surf.mBumpTextures;
            break;
        case AI_LWO_TRAN:
            listRef = &surf.mOpacityTextures;
            break;
        case AI_LWO_REFL:
            listRef = &surf.mReflectionTextures;
            break;
        default:
            ASSIMP_LOG_WARN("LWO2: Encountered unknown texture type");
            return;
    }

    // now attach the texture to the parent surface - sort by ordinal string
    for (TextureList::iterator it = listRef->begin(); it != listRef->end(); ++it) {
        if (::strcmp(tex.ordinal.c_str(), (*it).ordinal.c_str()) < 0) {
            listRef->insert(it, tex);
            return;
        }
    }
    listRef->push_back(tex);
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2ShaderBlock(LE_NCONST IFF::SubChunkHeader * /*head*/, unsigned int size) {
    LE_NCONST uint8_t *const end = mFileBuffer + size;

    ai_assert(!mSurfaces->empty());
    LWO::Surface &surf = mSurfaces->back();
    LWO::Shader shader;

    // get the ordinal string
    GetS0(shader.ordinal, size);

    // we could crash later if this is an empty string ...
    if (!shader.ordinal.length()) {
        ASSIMP_LOG_ERROR("LWO2: Ill-formed SURF.BLOK ordinal string");
        shader.ordinal = "\x00";
    }

    // read the header
    while (true) {
        if (mFileBuffer + 6 >= end) break;
        const IFF::SubChunkHeader head = IFF::LoadSubChunk(mFileBuffer);

        if (mFileBuffer + head.length > end)
            throw DeadlyImportError("LWO2: Invalid shader header chunk length");

        uint8_t *const next = mFileBuffer + head.length;
        switch (head.type) {
            case AI_LWO_ENAB:
                shader.enabled = GetU2() ? true : false;
                break;

            case AI_LWO_FUNC:
                GetS0(shader.functionName, head.length);
        }
        mFileBuffer = next;
    }

    // now attach the shader to the parent surface - sort by ordinal string
    for (ShaderList::iterator it = surf.mShaders.begin(); it != surf.mShaders.end(); ++it) {
        if (::strcmp(shader.ordinal.c_str(), (*it).ordinal.c_str()) < 0) {
            surf.mShaders.insert(it, shader);
            return;
        }
    }
    surf.mShaders.push_back(shader);
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2Surface(unsigned int size) {
    LE_NCONST uint8_t *const end = mFileBuffer + size;

    mSurfaces->push_back(LWO::Surface());
    LWO::Surface &surf = mSurfaces->back();

    GetS0(surf.mName, size);

    // check whether this surface was derived from any other surface
    std::string derived;
    GetS0(derived, (unsigned int)(end - mFileBuffer));
    if (derived.length()) {
        // yes, find this surface
        for (SurfaceList::iterator it = mSurfaces->begin(), itEnd = mSurfaces->end() - 1; it != itEnd; ++it) {
            if ((*it).mName == derived) {
                // we have it ...
                surf = *it;
                derived.clear();
                break;
            }
        }
        if (derived.size()) {
            ASSIMP_LOG_WARN("LWO2: Unable to find source surface: ", derived);
        }
    }

    while (true) {
        if (mFileBuffer + 6 >= end)
            break;
        const IFF::SubChunkHeader head = IFF::LoadSubChunk(mFileBuffer);

        if (mFileBuffer + head.length > end)
            throw DeadlyImportError("LWO2: Invalid surface chunk length");

        uint8_t *const next = mFileBuffer + head.length;
        switch (head.type) {
                // diffuse color
            case AI_LWO_COLR: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, COLR, 12);
                surf.mColor.r = GetF4();
                surf.mColor.g = GetF4();
                surf.mColor.b = GetF4();
                break;
            }
                // diffuse strength ... hopefully
            case AI_LWO_DIFF: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, DIFF, 4);
                surf.mDiffuseValue = GetF4();
                break;
            }
                // specular strength ... hopefully
            case AI_LWO_SPEC: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, SPEC, 4);
                surf.mSpecularValue = GetF4();
                break;
            }
                // transparency
            case AI_LWO_TRAN: {
                // transparency explicitly disabled?
                if (surf.mTransparency == 10e10f)
                    break;

                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, TRAN, 4);
                surf.mTransparency = GetF4();
                break;
            }
                // additive transparency
            case AI_LWO_ADTR: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, ADTR, 4);
                surf.mAdditiveTransparency = GetF4();
                break;
            }
                // wireframe mode
            case AI_LWO_LINE: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, LINE, 2);
                if (GetU2() & 0x1)
                    surf.mWireframe = true;
                break;
            }
                // glossiness
            case AI_LWO_GLOS: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, GLOS, 4);
                surf.mGlossiness = GetF4();
                break;
            }
                // bump intensity
            case AI_LWO_BUMP: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, BUMP, 4);
                surf.mBumpIntensity = GetF4();
                break;
            }
                // color highlights
            case AI_LWO_CLRH: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, CLRH, 4);
                surf.mColorHighlights = GetF4();
                break;
            }
                // index of refraction
            case AI_LWO_RIND: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, RIND, 4);
                surf.mIOR = GetF4();
                break;
            }
                // polygon sidedness
            case AI_LWO_SIDE: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, SIDE, 2);
                surf.bDoubleSided = (3 == GetU2());
                break;
            }
                // maximum smoothing angle
            case AI_LWO_SMAN: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, SMAN, 4);
                surf.mMaximumSmoothAngle = std::fabs(GetF4());
                break;
            }
                // vertex color channel to be applied to the surface
            case AI_LWO_VCOL: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, VCOL, 12);
                surf.mDiffuseValue *= GetF4(); // strength
                ReadVSizedIntLWO2(mFileBuffer); // skip envelope
                surf.mVCMapType = GetU4(); // type of the channel

                // name of the channel
                GetS0(surf.mVCMap, (unsigned int)(next - mFileBuffer));
                break;
            }
                // surface bock entry
            case AI_LWO_BLOK: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, BLOK, 4);
                IFF::SubChunkHeader head2 = IFF::LoadSubChunk(mFileBuffer);

                switch (head2.type) {
                    case AI_LWO_PROC:
                    case AI_LWO_GRAD:
                    case AI_LWO_IMAP:
                        LoadLWO2TextureBlock(&head2, head.length);
                        break;
                    case AI_LWO_SHDR:
                        LoadLWO2ShaderBlock(&head2, head.length);
                        break;

                    default:
                        ASSIMP_LOG_WARN("LWO2: Found an unsupported surface BLOK");
                };

                break;
            }
        }
        mFileBuffer = next;
    }
}

#endif // !! ASSIMP_BUILD_NO_X_IMPORTER
