FBX2glTF/src/fbx/materials/TraditionalMaterials.cpp

/**
 * Copyright (c) 2014-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#include "TraditionalMaterials.hpp"

std::unique_ptr<FbxTraditionalMaterialInfo> FbxTraditionalMaterialResolver::resolve() const
{
    auto getSurfaceScalar = [&](const char *propName) -> std::tuple<FbxDouble, FbxFileTexture *> {
        const FbxProperty prop = fbxMaterial->FindProperty(propName);

        FbxDouble val(0);
        FbxFileTexture *tex = prop.GetSrcObject<FbxFileTexture>();
        if (tex != nullptr && textureLocations.find(tex) == textureLocations.end()) {
            tex = nullptr;
        }
        if (tex == nullptr && prop.IsValid()) {
            val = prop.Get<FbxDouble>();
        }
        return std::make_tuple(val, tex);
    };

    auto getSurfaceVector = [&](const char *propName) -> std::tuple<FbxDouble3, FbxFileTexture *> {
        const FbxProperty prop = fbxMaterial->FindProperty(propName);

        FbxDouble3 val(1, 1, 1);
        FbxFileTexture *tex = prop.GetSrcObject<FbxFileTexture>();
        if (tex != nullptr && textureLocations.find(tex) == textureLocations.end()) {
            tex = nullptr;
        }
        if (tex == nullptr && prop.IsValid()) {
            val = prop.Get<FbxDouble3>();
        }
        return std::make_tuple(val, tex);
    };

    auto getSurfaceValues = [&](const char *colName, const char *facName) -> std::tuple<FbxVector4, FbxFileTexture *, FbxFileTexture *> {
        const FbxProperty colProp = fbxMaterial->FindProperty(colName);
        const FbxProperty facProp = fbxMaterial->FindProperty(facName);

        FbxDouble3 colorVal(1, 1, 1);
        FbxDouble  factorVal(1);

        FbxFileTexture *colTex = colProp.GetSrcObject<FbxFileTexture>();
        if (colTex != nullptr && textureLocations.find(colTex) == textureLocations.end()) {
            colTex = nullptr;
        }
        if (colTex == nullptr && colProp.IsValid()) {
            colorVal = colProp.Get<FbxDouble3>();
        }
        FbxFileTexture *facTex = facProp.GetSrcObject<FbxFileTexture>();
        if (facTex != nullptr && textureLocations.find(facTex) == textureLocations.end()) {
            facTex = nullptr;
        }
        if (facTex == nullptr && facProp.IsValid()) {
            factorVal = facProp.Get<FbxDouble>();
        }

        auto val = FbxVector4(
            colorVal[0] * factorVal,
            colorVal[1] * factorVal,
            colorVal[2] * factorVal,
            factorVal);
        return std::make_tuple(val, colTex, facTex);
    };

    std::string name = fbxMaterial->GetName();
    std::unique_ptr<FbxTraditionalMaterialInfo> res(new FbxTraditionalMaterialInfo(name.c_str(), fbxMaterial->ShadingModel.Get()));

    // four properties are on the same structure and follow the same rules
    auto handleBasicProperty = [&](const char *colName, const char *facName) -> std::tuple<FbxVector4, FbxFileTexture *>{
        FbxFileTexture *colTex, *facTex;
        FbxVector4     vec;

        std::tie(vec, colTex, facTex) = getSurfaceValues(colName, facName);
        if (colTex) {
            if (facTex) {
                fmt::printf("Warning: Mat [%s]: Can't handle both %s and %s textures; discarding %s.\n", name, colName, facName, facName);
            }
            return std::make_tuple(vec, colTex);
        }
        return std::make_tuple(vec, facTex);
    };

    std::tie(res->colAmbient, res->texAmbient)   =
        handleBasicProperty(FbxSurfaceMaterial::sAmbient, FbxSurfaceMaterial::sAmbientFactor);
    std::tie(res->colSpecular, res->texSpecular) =
        handleBasicProperty(FbxSurfaceMaterial::sSpecular, FbxSurfaceMaterial::sSpecularFactor);
    std::tie(res->colDiffuse, res->texDiffuse)   =
        handleBasicProperty(FbxSurfaceMaterial::sDiffuse, FbxSurfaceMaterial::sDiffuseFactor);
    std::tie(res->colEmissive, res->texEmissive) =
        handleBasicProperty(FbxSurfaceMaterial::sEmissive, FbxSurfaceMaterial::sEmissiveFactor);

    // the normal map can only ever be a map, ignore everything else
    tie(std::ignore, res->texNormal) = getSurfaceVector(FbxSurfaceMaterial::sNormalMap);

    // shininess can be a map or a factor; afaict the map is always 'ShininessExponent' and the
    // value is always found in 'Shininess' but only sometimes in 'ShininessExponent'.
    tie(std::ignore, res->texShininess) = getSurfaceScalar("ShininessExponent");
    tie(res->shininess, std::ignore)    = getSurfaceScalar("Shininess");

    // for transparency we just want a constant vector value;
    FbxVector4 transparency;
    // extract any existing textures only so we can warn that we're throwing them away
    FbxFileTexture *colTex, *facTex;
    std::tie(transparency, colTex, facTex) =
        getSurfaceValues(FbxSurfaceMaterial::sTransparentColor, FbxSurfaceMaterial::sTransparencyFactor);
    if (colTex) {
        fmt::printf("Warning: Mat [%s]: Can't handle texture for %s; discarding.\n", name, FbxSurfaceMaterial::sTransparentColor);
    }
    if (facTex) {
        fmt::printf("Warning: Mat [%s]: Can't handle texture for %s; discarding.\n", name, FbxSurfaceMaterial::sTransparencyFactor);
    }
    // FBX color is RGB, so we calculate the A channel as the average of the FBX transparency color vector
    res->colDiffuse[3] = 1.0 - (transparency[0] + transparency[1] + transparency[2])/3.0;

    return res;
}