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c++ - 使用 FBX SDK 获取索引

转载 作者:行者123 更新时间:2023-11-30 05:00:03 24 4
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我无法确定使用什么从 FBX 文件中获取索引。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取索引。

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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,我遍历面(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);
}

这样做对于只包含一个网格的 FBX 效果很好,但是当有多个网格时,它似乎无法缝合面。如果这来 self 正在使用的数据结构,我将进一步彻底调查,但如果有人发现这方面的问题,请告诉我。

问题在于法线和纹理坐标的索引,我不知道如何获取。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;
}

我现在只处理面 [vertices] 的情况,我认为它对 texcoords 是正确的(我现在没有得到 Material 所以我无法检查)。但是对于法线,我找不到任何关于获取他们的索引的信息;这就是为什么我只复制与位置相同的索引,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 { /*...*/ }
}
}

这是恢复索引的正确方法吗?我错过了什么吗?

最佳答案

首先,您不应该将所有网格的数据都放在同一个数组中。每个网格可以有不同的 Material ,所以应该用单独的 drawcall 绘制。但是,如果这不是您的选择,那么该行就会出错:

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

你把顶点放在一个数组中,像这样

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

但是 mesh->GetPolygonVertex(polyIndex, polyVertIndex) 返回相对当前网格的索引,因此第二个网格不是从 V52 开始,而是从 V1。所以你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 更好地进入同一个循环,你得到索引。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++;
}
}

关于c++ - 使用 FBX SDK 获取索引,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50926809/

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