使用FBX SDK获取索引

Question

我无法确定从FBX文件中获取索引的内容。恢复数据非常好（至少对于位置而言），但我似乎无法找到如何获得指数。

免责声明：对于长段代码感到抱歉，如果您认为某些部分确实没必要，请随时修改。

我目前正在获取这样的数据：

// Recovering geometry
for (int meshIndex = 0; meshIndex < scene->GetGeometryCount(); ++meshIndex)
{
  const auto mesh = static_cast<FbxMesh*>(scene->GetGeometry(meshIndex));

  // Recovering positions
  int currentVertIndex = points_coords.size();
  points_coords.resize(currentVertIndex + mesh->GetControlPointsCount(), std::vector<coord_type>(3));

  for (int vertIndex = 0; vertIndex < mesh->GetControlPointsCount(); ++vertIndex, ++currentVertIndex)
  {
    const auto& vertPos = mesh->GetControlPointAt(vertIndex);

    points_coords[currentVertIndex][0] = vertPos[0]; // X position
    points_coords[currentVertIndex][1] = vertPos[1]; // Y position
    points_coords[currentVertIndex][2] = vertPos[2]; // Z position
  }

  // Iterate over normals with mesh->GetElementNormal()->GetDirectArray().GetCount()

  // Iterate over texcoords with mesh->GetElementUV()->GetDirectArray().GetCount()

至于索引，我正在迭代面（多边形）并获取它们的顶点索引：

// Fetching positions' indices
int currentPosPolyIndex = face_indices.size();
face_indices.resize(currentPosPolyIndex + mesh->GetPolygonCount());

for (int polyIndex = 0; polyIndex < mesh->GetPolygonCount(); ++polyIndex, ++currentPosPolyIndex)
{
  const auto polySize = mesh->GetPolygonSize(polyIndex);
  face_indices[currentPosPolyIndex].resize(polySize);

  for (int polyVertIndex = 0; polyVertIndex < polySize; ++polyVertIndex)
    face_indices[currentPosPolyIndex][polyVertIndex] = mesh->GetPolygonVertex(polyIndex, polyVertIndex);
}

对于仅包含一个网格的FBX，这样做效果很好，但是当有多个网格时，它似乎无法缝合面部。如果这些来自我正在使用的数据结构，我将进一步深入调查，但如果有人发现此问题，请告诉我。

问题在于正常情况和texcoords的指数，我无法想象如何获取。目前我正在检查两者的映射模式，并尝试相应地填充数据：

  const auto texMapping = mesh->GetElementUV()->GetMappingMode();

  if (texMapping == FbxLayerElement::EMappingMode::eByControlPoint)
  {
    std::cout << "[FbxFileReader] Mapping mesh's texture coordinates by vertex." << std::endl;

    texture_face_indices.resize(texture_face_indices.size() + mesh->GetPolygonCount());

    std::copy(face_indices.cend() - mesh->GetPolygonCount(), face_indices.cend(), texture_face_indices.end() - mesh->GetPolygonCount());
  }
  else if (texMapping == FbxLayerElement::EMappingMode::eByEdge)
  {
    std::cout << "[FbxFileReader] Mapping mesh's texture coordinates by halfedge." << std::endl;
  }
  else if (texMapping == FbxLayerElement::EMappingMode::eByPolygon || texMapping == FbxLayerElement::EMappingMode::eByPolygonVertex)
  {
    std::cout << "[FbxFileReader] Mapping mesh's texture coordinates by face" << (texMapping == FbxLayerElement::EMappingMode::eByPolygonVertex ? " vertices" : "") << '.' << std::endl;

    int currentTexPolyIndex = texture_face_indices.size();
    texture_face_indices.resize(currentTexPolyIndex + mesh->GetPolygonCount());

    for (int polyIndex = 0; polyIndex < mesh->GetPolygonCount(); ++polyIndex, ++currentTexPolyIndex)
    {
      if (texMapping == FbxLayerElement::EMappingMode::eByPolygonVertex)
      {
        const auto polySize = mesh->GetPolygonSize(polyIndex);
        texture_face_indices[currentTexPolyIndex].resize(polySize);

        for (int polyVertIndex = 0; polyVertIndex < polySize; ++polyVertIndex)
          texture_face_indices[currentTexPolyIndex][polyVertIndex] = mesh->GetTextureUVIndex(polyIndex, polyVertIndex);
      }
      else
      {
        // Fetch face's texcoords & add it
        //texture_face_indices[currentTexPolyIndex].emplace_back(...);
      }
    }
  }
  else if (texMapping == FbxLayerElement::EMappingMode::eAllSame)
  {
    std::cout << "[FbxFileReader] Mapping mesh's texture coordinates by mesh." << std::endl;
  }
  else
  {
    std::cerr << "[FbxFileReader] Couldn't handle mesh's texture coordinates' mapping mode." << std::endl;
  }

我现在只处理face [vertices]的情况，我认为对于texcoords是正确的（我现在没有得到材料所以我无法检查）。但是对于普通人来说，我找不到任何有关获得他们指数的信息;这就是为什么我只复制与position'相同的索引，我认为这是完全错误的：

  // Same checks for normals
  else if (normMapping == FbxLayerElement::EMappingMode::eByPolygon || normMapping == FbxLayerElement::EMappingMode::eByPolygonVertex)
  {
    std::cout << "[FbxFileReader] Mapping mesh's normals by face" << (normMapping == FbxLayerElement::EMappingMode::eByPolygonVertex ? " vertices" : "") << "." << std::endl;

    int currentNormPolyIndex = normal_face_indices.size();
    normal_face_indices.resize(currentNormPolyIndex + mesh->GetPolygonCount());

    for (int polyIndex = 0; polyIndex < mesh->GetPolygonCount(); ++polyIndex, ++currentNormPolyIndex)
    {
      if (normMapping == FbxLayerElement::EMappingMode::eByPolygonVertex)
      {
        const auto polySize = mesh->GetPolygonSize(polyIndex);
        normal_face_indices[currentNormPolyIndex].resize(polySize);

        for (int polyVertIndex = 0; polyVertIndex < polySize; ++polyVertIndex)
          normal_face_indices[currentNormPolyIndex][polyVertIndex] = face_indices[currentNormPolyIndex][polyVertIndex];
      }
      else { /*...*/ }
    }
  }

这是恢复指数的正确方法吗？我错过了什么吗？

Answer 1

首先，您不应该将所有网格物体的数据放入同一数组。每个网格可以具有不同的材质，因此应使用单独的drawcall进行绘制。但是，如果这不是您的选择，那么错误就在该行中：

face_indices[currentPosPolyIndex][polyVertIndex] = mesh->GetPolygonVertex(polyIndex, polyVertIndex);

您将顶点放置在单个数组中，就像这样

[(1-st mesh) V1, V2, V3, ..., (2-nd mesh) V52, V53, V54, ...]

但是mesh->GetPolygonVertex(polyIndex, polyVertIndex)返回索引相对当前的网格，因此第二个网格不是从V52开始，而是从V1开始。因此，您应该计算一些偏移量。

int currentVertIndex = points_coords.size();
int meshVertIndexStart = currentVertIndex;
...
for (int polyVertIndex = 0; polyVertIndex < polySize; ++polyVertIndex)
    face_indices[currentPosPolyIndex][polyVertIndex] = meshVertIndexStart + mesh->GetPolygonVertex(polyIndex, polyVertIndex);

法线和UV最好能在获得索引时进入同一循环。这是一些代码

FbxVector4 getNormal(FbxGeometryElementNormal* normalElement, int polyIndex, int posIndex) {
    if (normalElement->GetMappingMode() == FbxGeometryElement::eByControlPoint) {
        if (normalElement->GetReferenceMode() == FbxGeometryElement::eDirect)
            return normalElement->GetDirectArray().GetAt(posIndex);
        int i = normalElement->GetIndexArray().GetAt(posIndex);
        return normalElement->GetDirectArray().GetAt(i);
    }
    else if (normalElement->GetMappingMode() == FbxGeometryElement::eByPolygonVertex) {
        if (normalElement->GetReferenceMode() == FbxGeometryElement::eDirect)
            return normalElement->GetDirectArray().GetAt(polyIndex);
        int i = normalElement->GetIndexArray().GetAt(polyIndex);
        return normalElement->GetDirectArray().GetAt(i);
    }
    return FbxVector4();
}

FbxVector2 getUV(FbxGeometryElementUV* uvElement, int polyIndex, int posIndex) {
    if (uvElement->GetMappingMode() == FbxGeometryElement::eByControlPoint) {
        if (uvElement->GetReferenceMode() == FbxGeometryElement::eDirect)
            return uvElement->GetDirectArray().GetAt(posIndex);
        int i = uvElement->GetIndexArray().GetAt(posIndex);
        return uvElement->GetDirectArray().GetAt(i);
    }
    else if (uvElement->GetMappingMode() == FbxGeometryElement::eByPolygonVertex) {
        if (uvElement->GetReferenceMode() == FbxGeometryElement::eDirect)
            return uvElement->GetDirectArray().GetAt(polyIndex);
        int i = uvElement->GetIndexArray().GetAt(polyIndex);
        return uvElement->GetDirectArray().GetAt(i);
    }
    return FbxVector2();
}

...

int vertNum = 0;

for (int polyIndex = 0; polyIndex < mesh->GetPolygonCount(); ++polyIndex, ++currentPosPolyIndex) {
    const auto polySize = mesh->GetPolygonSize(polyIndex);
    face_indices[currentPosPolyIndex].resize(polySize);

    for (int polyVertIndex = 0; polyVertIndex < polySize; ++polyVertIndex) {
        int vertIndex = mesh->GetPolygonVertex(polyIndex, polyVertIndex);
        face_indices[currentPosPolyIndex][polyVertIndex] = meshVertIndexStart + vertIndex;

        FbxVector4 normal = getNormal(mesh->GetElementNormal(), vertNum, vertIndex);
        FbxVector2 uv = getUV(mesh->GetElementUV(), vertNum, vertIndex);
        vertNum++;
    }
}