Merge pull request #24961 from savuor:rv/ply_mesh

PLY mesh support #24961

**Warning:** The PR changes exising API.

Fixes #24960
Connected PR: [#1145@extra](https://github.com/opencv/opencv_extra/pull/1145)

### Changes
* Adds faces loading from and saving to PLY files
* Fixes incorrect PLY loading (see issue)
* Adds per-vertex color loading / saving

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

doc/tutorials/3d/point_cloud/point_cloud.markdown

@@ -66,7 +66,7 @@ For that we use special functions to load mesh data and display it.
 Here for now only .OBJ files are supported and they should be triangulated before processing (triangulation - process of breaking faces into triangles).
 
 @code{.py}
-vertices, _, indices = cv2.loadMesh("../data/teapot.obj")
+vertices, indices = cv2.loadMesh("../data/teapot.obj")
 vertices = np.squeeze(vertices, axis=1)
 
 cv2.viz3d.showMesh("window", "mesh", vertices, indices)

modules/3d/include/opencv2/3d.hpp

@@ -2785,12 +2785,15 @@ CV_EXPORTS_W void savePointCloud(const String &filename, InputArray vertices, In
 *
 * Currently, the following file formats are supported:
 * -  [Wavefront obj file *.obj](https://en.wikipedia.org/wiki/Wavefront_.obj_file) (ONLY TRIANGULATED FACES)
+* -  [Polygon File Format *.ply](https://en.wikipedia.org/wiki/PLY_(file_format))
 * @param filename Name of the file.
 * @param vertices (vector of Point3f) vertex coordinates of a mesh
-* @param normals (vector of Point3f) vertex normals of a mesh
 * @param indices (vector of vectors of int) vertex normals of a mesh
+* @param normals (vector of Point3f) vertex normals of a mesh
+* @param colors (vector of Point3f) vertex colors of a mesh
 */
-CV_EXPORTS_W void loadMesh(const String &filename, OutputArray vertices, OutputArray normals, OutputArrayOfArrays indices);
+CV_EXPORTS_W void loadMesh(const String &filename, OutputArray vertices, OutputArrayOfArrays indices,
+                           OutputArray normals = noArray(), OutputArray colors = noArray());
 
 /** @brief Saves a mesh to a specified file.
 *
@@ -2799,11 +2802,12 @@ CV_EXPORTS_W void loadMesh(const String &filename, OutputArray vertices, OutputA
 *
 * @param filename Name of the file.
 * @param vertices (vector of Point3f) vertex coordinates of a mesh
-* @param normals (vector of Point3f) vertex normals of a mesh
 * @param indices (vector of vectors of int) vertex normals of a mesh
+* @param normals (vector of Point3f) vertex normals of a mesh
+* @param colors (vector of Point3f) vertex colors of a mesh
 */
-CV_EXPORTS_W void saveMesh(const String &filename, InputArray vertices, InputArray normals, InputArrayOfArrays indices);
-
+CV_EXPORTS_W void saveMesh(const String &filename, InputArray vertices, InputArrayOfArrays indices,
+                           InputArray normals = noArray(), InputArray colors = noArray());
 
 //! @} _3d
 } //end namespace cv

modules/3d/src/pointcloud/io_ply.cpp

@@ -8,6 +8,8 @@
 #include <opencv2/core/utils/logger.hpp>
 #include <fstream>
 #include <string>
+#include <iomanip>
+#include <cstddef>
 
 namespace cv {
 
@@ -16,15 +18,16 @@ void PlyDecoder::readData(std::vector<Point3f> &points, std::vector<Point3f> &no
     points.clear();
     normals.clear();
     rgb.clear();
-    CV_UNUSED(indices);
+    indices.clear();
 
     std::ifstream file(m_filename, std::ios::binary);
     if (parseHeader(file))
     {
-        parseBody(file, points, normals, rgb);
+        parseBody(file, points, normals, rgb, indices);
     }
 }
 
+
 bool PlyDecoder::parseHeader(std::ifstream &file)
 {
     std::string s;
@@ -36,6 +39,11 @@ bool PlyDecoder::parseHeader(std::ifstream &file)
     }
     std::getline(file, s);
     auto splitArr = split(s, ' ');
+    // "\r" symbols are not trimmed by default
+    for (auto& e : splitArr)
+    {
+        e = trimSpaces(e);
+    }
     if (splitArr[0] != "format")
     {
         CV_LOG_ERROR(NULL, "Provided file doesn't have format");
@@ -59,63 +67,240 @@ bool PlyDecoder::parseHeader(std::ifstream &file)
         return false;
     }
 
-    bool onVertexRead = false;
+    const std::map<std::string, int> dataTypes =
+    {
+        { "char",   CV_8S  }, { "int8",    CV_8S  },
+        { "uchar",  CV_8U  }, { "uint8",   CV_8U  },
+        { "short",  CV_16S }, { "int16",   CV_16S },
+        { "ushort", CV_16U }, { "uint16",  CV_16U },
+        { "int",    CV_32S }, { "int32",   CV_32S },
+        { "uint",   CV_32U }, { "uint32",  CV_32U },
+        { "float",  CV_32F }, { "float32", CV_32F },
+        { "double", CV_64F }, { "float64", CV_64F },
+    };
+
+    enum ReadElement
+    {
+        READ_OTHER  = 0,
+        READ_VERTEX = 1,
+        READ_FACE   = 2
+    };
+    ReadElement elemRead = READ_OTHER;
+    m_vertexDescription = ElementDescription();
+    m_faceDescription = ElementDescription();
     while (std::getline(file, s))
     {
         if (startsWith(s, "element"))
         {
-            auto splitArrElem = split(s, ' ');
-            if (splitArrElem[1] == "vertex")
+            std::vector<std::string> splitArrElem = split(s, ' ');
+            // "\r" symbols are not trimmed by default
+            for (auto& e : splitArrElem)
             {
-                onVertexRead = true;
+                e = trimSpaces(e);
+            }
+            std::string elemName = splitArrElem.at(1);
+            if (elemName == "vertex")
+            {
+                elemRead = READ_VERTEX;
+                if(splitArrElem.size() != 3)
+                {
+                    CV_LOG_ERROR(NULL, "Vertex element description has " << splitArrElem.size()
+                                 << " words instead of 3");
+                    return false;
+                }
                 std::istringstream iss(splitArrElem[2]);
-                iss >> m_vertexCount;
+                iss >> m_vertexDescription.amount;
+            }
+            else if (elemName == "face")
+            {
+                elemRead = READ_FACE;
+                if(splitArrElem.size() != 3)
+                {
+                    CV_LOG_ERROR(NULL, "Face element description has " << splitArrElem.size()
+                                 << " words instead of 3");
+                    return false;
+                }
+                std::istringstream iss(splitArrElem[2]);
+                iss >> m_faceDescription.amount;
             }
             else
             {
-                onVertexRead = false;
+                elemRead = READ_OTHER;
             }
             continue;
         }
         if (startsWith(s, "property"))
         {
-            if (onVertexRead)
+            Property property;
+            std::string elName = (elemRead == READ_VERTEX) ? "Vertex" : "Face";
+            std::vector<std::string> splitArrElem = split(s, ' ');
+            // "\r" symbols are not trimmed by default
+            for (auto& e : splitArrElem)
             {
-                auto splitArrElem = split(s, ' ');
-                if (splitArrElem[2] == "x" || splitArrElem[2] == "y" || splitArrElem[2] == "z")
-                {
-                    if (splitArrElem[1] != "float") {
-                        CV_LOG_ERROR(NULL, "Provided property '" << splitArrElem[2] << "' with format '" << splitArrElem[1]
-                        << "' is not supported");
-                        return false;
-                    }
-                }
-                if (splitArrElem[2] == "red" || splitArrElem[2] == "green" || splitArrElem[2] == "blue")
-                {
-                    if (splitArrElem[1] != "uchar") {
-                        CV_LOG_ERROR(NULL, "Provided property '" << splitArrElem[2] << "' with format '" << splitArrElem[1]
-                        << "' is not supported");
-                        return false;
-                    }
-                    m_hasColour = true;
-                }
-                if (splitArrElem[2] == "nx")
-                {
-                    if (splitArrElem[1] != "float") {
-                        CV_LOG_ERROR(NULL, "Provided property '" << splitArrElem[2] << "' with format '" << splitArrElem[1]
-                        << "' is not supported");
-                        return false;
-                    }
-                    m_hasNormal = true;
-                }
+                e = trimSpaces(e);
             }
+            if (splitArrElem.size() < 3)
+            {
+                CV_LOG_ERROR(NULL, elName << " property has " << splitArrElem.size()
+                             << " words instead of at least 3");
+                return false;
+            }
+            std::string propType = splitArrElem[1];
+            if (propType == "list")
+            {
+                property.isList = true;
+                if (splitArrElem.size() < 5)
+                {
+                    CV_LOG_ERROR(NULL, elName << " property has " << splitArrElem.size()
+                                 << " words instead of at least 5");
+                    return false;
+                }
+                std::string amtTypeString = splitArrElem[2];
+                if (dataTypes.count(amtTypeString) == 0)
+                {
+                    CV_LOG_ERROR(NULL, "Property type " << amtTypeString
+                                 << " is not supported");
+                    return false;
+                }
+                else
+                {
+                    property.counterType = dataTypes.at(amtTypeString);
+                }
+                std::string idxTypeString = splitArrElem[3];
+                if (dataTypes.count(idxTypeString) == 0)
+                {
+                    CV_LOG_ERROR(NULL, "Property type " << idxTypeString
+                                 << " is not supported");
+                    return false;
+                }
+                else
+                {
+                    property.valType = dataTypes.at(idxTypeString);
+                }
+
+                property.name = splitArrElem[4];
+            }
+            else
+            {
+                property.isList = false;
+                if (dataTypes.count(propType) == 0)
+                {
+                    CV_LOG_ERROR(NULL, "Property type " << propType
+                                 << " is not supported");
+                    return false;
+                }
+                else
+                {
+                    property.valType = dataTypes.at(propType);
+                }
+                property.name = splitArrElem[2];
+            }
+
+            if (elemRead == READ_VERTEX)
+            {
+                m_vertexDescription.properties.push_back(property);
+            }
+            else if (elemRead == READ_FACE)
+            {
+                m_faceDescription.properties.push_back(property);
+            }
+
             continue;
         }
         if (startsWith(s, "end_header"))
             break;
-
     }
-    return true;
+
+    bool good = true;
+    m_vertexCount = m_vertexDescription.amount;
+    std::map<std::string, int> amtProps;
+    for (const auto& p : m_vertexDescription.properties)
+    {
+        bool known = false;
+        if (p.name ==  "x" || p.name ==  "y" || p.name ==  "z")
+        {
+            known = true;
+            if (p.valType != CV_32F)
+            {
+                CV_LOG_ERROR(NULL, "Vertex property " << p.name
+                                                      << " should be float");
+                good = false;
+            }
+        }
+        if (p.name == "nx" || p.name == "ny" || p.name == "nz")
+        {
+            known = true;
+            if (p.valType != CV_32F)
+            {
+                CV_LOG_ERROR(NULL, "Vertex property " << p.name
+                                                      << " should be float");
+                good = false;
+            }
+            m_hasNormal = true;
+        }
+        if (p.name ==  "red" || p.name ==  "green" || p.name ==  "blue")
+        {
+            known = true;
+            if (p.valType != CV_8U)
+            {
+                CV_LOG_ERROR(NULL, "Vertex property " << p.name
+                                                      << " should be uchar");
+                good = false;
+            }
+            m_hasColour = true;
+        }
+        if (p.isList)
+        {
+            CV_LOG_ERROR(NULL, "List properties for vertices are not supported");
+            good = false;
+        }
+        if (known)
+        {
+            amtProps[p.name]++;
+        }
+    }
+
+    // check if we have no duplicates
+    for (const auto& a : amtProps)
+    {
+        if (a.second > 1)
+        {
+            CV_LOG_ERROR(NULL, "Vertex property " << a.first << " is duplicated");
+            good = false;
+        }
+    }
+    const std::array<std::string, 3> vertKeys = {"x", "y", "z"};
+    for (const std::string& c : vertKeys)
+    {
+        if (amtProps.count(c) == 0)
+        {
+            CV_LOG_ERROR(NULL, "Vertex property " << c << " is not presented in the file");
+            good = false;
+        }
+    }
+
+    m_faceCount = m_faceDescription.amount;
+    int amtLists = 0;
+    for (const auto& p : m_faceDescription.properties)
+    {
+        if (p.isList)
+        {
+            amtLists++;
+            if (!(p.counterType == CV_8U && (p.valType == CV_32S || p.valType == CV_32U)))
+            {
+                CV_LOG_ERROR(NULL, "List property " << p.name
+                             << " should have type uint8 for counter and uint32 for values");
+                good = false;
+            }
+        }
+    }
+    if (amtLists > 1)
+    {
+        CV_LOG_ERROR(NULL, "Only 1 list property is supported per face");
+        good = false;
+    }
+
+    return good;
 }
 
 template <typename T>
@@ -142,42 +327,185 @@ T readNext(std::ifstream &file, DataFormat format)
     return val;
 }
 
-void PlyDecoder::parseBody(std::ifstream &file, std::vector<Point3f> &points, std::vector<Point3f> &normals, std::vector<Point3_<uchar>> &rgb)
+template <>
+uchar readNext<uchar>(std::ifstream &file, DataFormat format)
+{
+    if (format == DataFormat::ASCII)
+    {
+        int val;
+        file >> val;
+        return (uchar)val;
+    }
+    uchar val;
+    file.read((char *)&val, sizeof(uchar));
+    // 1 byte does not have to be endian-swapped
+    return val;
+}
+
+void PlyDecoder::parseBody(std::ifstream &file, std::vector<Point3f> &points, std::vector<Point3f> &normals, std::vector<Point3_<uchar>> &rgb,
+                           std::vector<std::vector<int32_t>> &indices)
 {
     points.reserve(m_vertexCount);
+    if (m_hasColour)
+    {
+        rgb.reserve(m_vertexCount);
+    }
     if (m_hasNormal)
     {
         normals.reserve(m_vertexCount);
     }
+
+    struct VertexFields
+    {
+        float vx, vy, vz;
+        float nx, ny, nz;
+        uchar r, g, b;
+    };
+
+    union VertexData
+    {
+        std::array<uchar, 27> bytes;
+        VertexFields vf;
+    };
+
+    // to avoid string matching at file loading
+    std::vector<size_t> vertexOffsets(m_vertexDescription.properties.size(), (size_t)(-1));
+    for (size_t j = 0; j < m_vertexDescription.properties.size(); j++)
+    {
+        const auto& p = m_vertexDescription.properties[j];
+        size_t offset = 0;
+        if (p.name == "x")
+            offset = offsetof(VertexFields, vx);
+        if (p.name == "y")
+            offset = offsetof(VertexFields, vy);
+        if (p.name == "z")
+            offset = offsetof(VertexFields, vz);
+        if (p.name == "nx")
+            offset = offsetof(VertexFields, nx);
+        if (p.name == "ny")
+            offset = offsetof(VertexFields, ny);
+        if (p.name == "nz")
+            offset = offsetof(VertexFields, nz);
+        if (p.name == "red")
+            offset = offsetof(VertexFields, r);
+        if (p.name == "green")
+            offset = offsetof(VertexFields, g);
+        if (p.name == "blue")
+            offset = offsetof(VertexFields, b);
+        vertexOffsets[j] = offset;
+    }
+
     for (size_t i = 0; i < m_vertexCount; i++)
     {
-        Point3f vertex;
-        vertex.x = readNext<float>(file, m_inputDataFormat);
-        vertex.y = readNext<float>(file, m_inputDataFormat);
-        vertex.z = readNext<float>(file, m_inputDataFormat);
-        points.push_back(vertex);
+        VertexData vertexData{ };
+        for (size_t j = 0; j < m_vertexDescription.properties.size(); j++)
+        {
+            const auto& p = m_vertexDescription.properties[j];
+            uint ival = 0; float fval = 0;
+            // here signedness is not important
+            switch (p.valType)
+            {
+            case CV_8U: case CV_8S:
+                ival = readNext<uchar>(file, m_inputDataFormat);
+                break;
+            case CV_16U: case CV_16S:
+                ival = readNext<ushort>(file, m_inputDataFormat);
+                break;
+            case CV_32S: case CV_32U:
+                ival = readNext<uint>(file, m_inputDataFormat);
+                break;
+            case CV_32F:
+                fval = readNext<float>(file, m_inputDataFormat);
+                break;
+            case CV_64F:
+                fval = (float)readNext<double>(file, m_inputDataFormat);
+                break;
+            default:
+                break;
+            }
+            size_t offset = vertexOffsets[j];
+            if (offset != (size_t)(-1))
+            {
+                switch (p.valType)
+                {
+                case CV_8U: case CV_8S:
+                    *(vertexData.bytes.data() + offset) = (uchar)ival;
+                    break;
+                case CV_32F:
+                    *(float*)(vertexData.bytes.data() + offset) = fval;
+                    break;
+                default:
+                    // the rest are unused
+                    break;
+                }
+            }
+        }
+
+        points.push_back({ vertexData.vf.vx, vertexData.vf.vy, vertexData.vf.vz });
         if (m_hasColour)
         {
-            Point3_<uchar> colour;
-            colour.x = readNext<int>(file, m_inputDataFormat) & 0xff;
-            colour.y = readNext<int>(file, m_inputDataFormat) & 0xff;
-            colour.z = readNext<int>(file, m_inputDataFormat) & 0xff;
-            rgb.push_back(colour);
+            rgb.push_back({ vertexData.vf.r, vertexData.vf.g, vertexData.vf.b });
         }
         if (m_hasNormal)
         {
-            Point3f normal;
-            normal.x = readNext<float>(file, m_inputDataFormat);
-            normal.y = readNext<float>(file, m_inputDataFormat);
-            normal.z = readNext<float>(file, m_inputDataFormat);
-            normals.push_back(normal);
+            normals.push_back({ vertexData.vf.nx, vertexData.vf.ny, vertexData.vf.nz });
+        }
+    }
+
+    indices.reserve(m_faceCount);
+    for (size_t i = 0; i < m_faceCount; i++)
+    {
+        for (const auto& p : m_faceDescription.properties)
+        {
+            if (p.isList)
+            {
+                size_t nVerts = readNext<uchar>(file, m_inputDataFormat);
+                if (nVerts < 3)
+                {
+                    CV_LOG_ERROR(NULL, "Face should have at least 3 vertices but has " << nVerts);
+                    return;
+                }
+                // PLY can have faces with >3 vertices in TRIANGLE_FAN format
+                // in this case we load them as separate triangles
+                int vert1 = readNext<int>(file, m_inputDataFormat);
+                int vert2 = readNext<int>(file, m_inputDataFormat);
+                for (size_t j = 2; j < nVerts; j++)
+                {
+                    int vert3 = readNext<int>(file, m_inputDataFormat);
+                    indices.push_back({vert1, vert2, vert3});
+                    vert2 = vert3;
+                }
+            }
+            else
+            {
+                // read and discard
+                switch (p.valType)
+                {
+                case CV_8U: case CV_8S:
+                    readNext<uchar>(file, m_inputDataFormat);
+                    break;
+                case CV_16U: case CV_16S:
+                    readNext<ushort>(file, m_inputDataFormat);
+                    break;
+                case CV_32S: case CV_32U:
+                    readNext<uint>(file, m_inputDataFormat);
+                    break;
+                case CV_32F:
+                    readNext<float>(file, m_inputDataFormat);
+                    break;
+                case CV_64F:
+                    readNext<double>(file, m_inputDataFormat);
+                    break;
+                default:
+                    break;
+                }
+            }
         }
     }
 }
 
 void PlyEncoder::writeData(const std::vector<Point3f> &points, const std::vector<Point3f> &normals, const std::vector<Point3_<uchar>> &rgb, const std::vector<std::vector<int32_t>> &indices)
 {
-    CV_UNUSED(indices);
     std::ofstream file(m_filename, std::ios::binary);
     if (!file) {
         CV_LOG_ERROR(NULL, "Impossible to open the file: " << m_filename);
@@ -194,7 +522,8 @@ void PlyEncoder::writeData(const std::vector<Point3f> &points, const std::vector
     file << "property float y" << std::endl;
     file << "property float z" << std::endl;
 
-    if(hasColor) {
+    if(hasColor)
+    {
         file << "property uchar red" << std::endl;
         file << "property uchar green" << std::endl;
         file << "property uchar blue" << std::endl;
@@ -207,17 +536,34 @@ void PlyEncoder::writeData(const std::vector<Point3f> &points, const std::vector
         file << "property float nz" << std::endl;
     }
 
-    file << "end_header" << std::endl;
+    if (!indices.empty())
+    {
+        file << "element face " << indices.size() << std::endl;
+        file << "property list uchar int vertex_indices" << std::endl;
+    }
 
+    file << "end_header" << std::endl;
 
     for (size_t i = 0; i < points.size(); i++)
     {
-        file << points[i].x << " " << points[i].y << " " << points[i].z;
-        if (hasColor) {
+        file << std::setprecision(9) << points[i].x << " " << points[i].y << " " << points[i].z;
+        if (hasColor)
+        {
             file << " " << static_cast<int>(rgb[i].x) << " " << static_cast<int>(rgb[i].y) << " " << static_cast<int>(rgb[i].z);
         }
-        if (hasNormals) {
-            file << " " << normals[i].x << " " << normals[i].y << " " << normals[i].z;
+        if (hasNormals)
+        {
+            file << " " << std::setprecision(9) << normals[i].x << " " << normals[i].y << " " << normals[i].z;
+        }
+        file << std::endl;
+    }
+
+    for (const auto& faceIndices : indices)
+    {
+        file << faceIndices.size();
+        for (const auto& index : faceIndices)
+        {
+            file << " " << index;
         }
         file << std::endl;
     }

modules/3d/src/pointcloud/io_ply.hpp

@@ -18,6 +18,20 @@ enum class DataFormat
     BinaryBigEndian
 };
 
+struct Property
+{
+    bool isList;
+    int counterType;
+    int valType;
+    std::string name;
+};
+
+struct ElementDescription
+{
+    size_t amount;
+    std::vector<Property> properties;
+};
+
 class PlyDecoder CV_FINAL : public BasePointCloudDecoder
 {
 public:
@@ -25,12 +39,16 @@ public:
 
 protected:
     bool parseHeader(std::ifstream &file);
-    void parseBody(std::ifstream &file, std::vector<Point3f> &points, std::vector<Point3f> &normals, std::vector<Point3_<uchar>> &rgb);
+    void parseBody(std::ifstream &file, std::vector<Point3f> &points, std::vector<Point3f> &normals, std::vector<Point3_<uchar>> &rgb,
+                   std::vector<std::vector<int32_t>> &indices);
 
     DataFormat m_inputDataFormat;
     size_t m_vertexCount{0};
+    size_t m_faceCount{0};
     bool m_hasColour{false};
     bool m_hasNormal{false};
+    ElementDescription m_vertexDescription;
+    ElementDescription m_faceDescription;
 };
 
 class PlyEncoder CV_FINAL : public BasePointCloudEncoder

modules/3d/src/pointcloud/load_point_cloud.cpp

@@ -122,12 +122,15 @@ void savePointCloud(const String &filename, InputArray vertices, InputArray norm
 #endif
 }
 
-void loadMesh(const String &filename, OutputArray vertices, OutputArray normals, OutputArrayOfArrays indices)
+void loadMesh(const String &filename, OutputArray vertices, OutputArrayOfArrays indices, OutputArray normals, OutputArray colors)
 {
 #if OPENCV_HAVE_FILESYSTEM_SUPPORT
+    CV_Assert(vertices.needed());
+    CV_Assert(indices.needed());
+
     PointCloudDecoder decoder = findDecoder(filename);
     String file_ext = getExtension(filename);
-    if (!decoder || (file_ext != "obj" && file_ext != "OBJ")) {
+    if (!decoder) {
         CV_LOG_ERROR(NULL, "File extension '" << file_ext << "' is not supported");
         return;
     }
@@ -141,15 +144,23 @@ void loadMesh(const String &filename, OutputArray vertices, OutputArray normals,
 
     decoder->readData(vec_vertices, vec_normals, vec_rgb, vec_indices);
 
-    if (!vec_vertices.empty()) {
+    if (!vec_vertices.empty())
+    {
         Mat(1, static_cast<int>(vec_vertices.size()), CV_32FC3, vec_vertices.data()).copyTo(vertices);
     }
 
-    if (!vec_normals.empty()) {
+    if (normals.needed() && !vec_normals.empty())
+    {
         Mat(1, static_cast<int>(vec_normals.size()), CV_32FC3, vec_normals.data()).copyTo(normals);
     }
 
-    if (!vec_indices.empty()) {
+    if (colors.needed() && !vec_rgb.empty())
+    {
+        Mat(1, static_cast<int>(vec_rgb.size()), CV_8UC3, vec_rgb.data()).convertTo(colors, CV_32F, (1.0/255.0));
+    }
+
+    if (!vec_indices.empty())
+    {
         std::vector<std::vector<int32_t>>& vec = *(std::vector<std::vector<int32_t>>*)indices.getObj();
         vec.resize(vec_indices.size());
         for (size_t i = 0; i < vec_indices.size(); ++i) {
@@ -161,11 +172,13 @@ void loadMesh(const String &filename, OutputArray vertices, OutputArray normals,
     CV_UNUSED(filename);
     CV_UNUSED(vertices);
     CV_UNUSED(normals);
+    CV_UNUSED(colors);
+    CV_UNUSED(indices);
     CV_LOG_WARNING(NULL, "File system support is disabled in this OpenCV build!");
 #endif
 }
 
-void saveMesh(const String &filename, InputArray vertices, InputArray normals, InputArrayOfArrays indices)
+void saveMesh(const String &filename, InputArray vertices, InputArrayOfArrays indices, InputArray normals, InputArray colors)
 {
 #if OPENCV_HAVE_FILESYSTEM_SUPPORT
     if (vertices.empty()) {
@@ -175,7 +188,7 @@ void saveMesh(const String &filename, InputArray vertices, InputArray normals, I
 
     auto encoder = findEncoder(filename);
     String file_ext = getExtension(filename);
-    if (!encoder || (file_ext != "obj" && file_ext != "OBJ")) {
+    if (!encoder) {
         CV_LOG_ERROR(NULL, "File extension '" << file_ext << "' is not supported");
         return;
     }
@@ -185,15 +198,22 @@ void saveMesh(const String &filename, InputArray vertices, InputArray normals, I
     std::vector<Point3f> vec_vertices(vertices.getMat());
     std::vector<Point3f> vec_normals;
     std::vector<Point3_<uchar>> vec_rgb;
-    if (!normals.empty()){
+    if (!normals.empty())
+    {
         vec_normals = normals.getMat();
     }
 
+    if (!colors.empty())
+    {
+        colors.getMat().convertTo(vec_rgb, CV_8U, 255.0);
+    }
+
     std::vector<Mat> mat_indices;
     indices.getMatVector(mat_indices);
     std::vector<std::vector<int32_t>> vec_indices(mat_indices.size());
 
-    for (size_t i = 0; i < mat_indices.size(); ++i) {
+    for (size_t i = 0; i < mat_indices.size(); ++i)
+    {
         mat_indices[i].copyTo(vec_indices[i]);
     }
 
@@ -202,7 +222,9 @@ void saveMesh(const String &filename, InputArray vertices, InputArray normals, I
 #else // OPENCV_HAVE_FILESYSTEM_SUPPORT
     CV_UNUSED(filename);
     CV_UNUSED(vertices);
+    CV_UNUSED(colors);
     CV_UNUSED(normals);
+    CV_UNUSED(indices);
     CV_LOG_WARNING(NULL, "File system support is disabled in this OpenCV build!");
 #endif
 

modules/3d/test/test_pointcloud.cpp

@@ -132,14 +132,14 @@ TEST(PointCloud, LoadSaveMeshObj)
     auto folder = cvtest::TS::ptr()->get_data_path();
     std::string new_path = tempfile("new_mesh.obj");
 
-    cv::loadMesh(folder + "pointcloudio/orig.obj", points, normals, indices);
-    cv::saveMesh(new_path, points, normals, indices);
+    cv::loadMesh(folder + "pointcloudio/orig.obj", points, indices, normals);
+    cv::saveMesh(new_path, points, indices, normals);
 
     std::vector<cv::Point3f> points_gold;
     std::vector<cv::Point3f> normals_gold;
     std::vector<std::vector<int32_t>> indices_gold;
 
-    cv::loadMesh(new_path, points_gold, normals_gold, indices_gold);
+    cv::loadMesh(new_path, points_gold, indices_gold, normals_gold);
 
     EXPECT_EQ(normals_gold, normals);
     EXPECT_EQ(points_gold, points);
@@ -148,29 +148,44 @@ TEST(PointCloud, LoadSaveMeshObj)
     std::remove(new_path.c_str());
 }
 
-TEST(PointCloud, LoadSaveMeshPly)
+typedef std::string PlyTestParamsType;
+typedef testing::TestWithParam<PlyTestParamsType> PlyTest;
+
+TEST_P(PlyTest, LoadSaveMesh)
 {
-    std::vector<cv::Point3f> points;
-    std::vector<cv::Point3f> normals;
-    std::vector<std::vector<int32_t>> indices;
+    std::string fname = GetParam();
+
+    std::vector<cv::Point3f> points_gold, normals_gold, colors_gold;
+    std::vector<std::vector<int32_t>> indices_gold;
 
     auto folder = cvtest::TS::ptr()->get_data_path();
     std::string new_path = tempfile("new_mesh.ply");
 
-    // we don't support meshes in PLY format right now but it should exit silently
-    cv::loadMesh(folder + "pointcloudio/orig.ply", points, normals, indices);
-    EXPECT_TRUE(points.empty());
-    EXPECT_TRUE(normals.empty());
-    EXPECT_TRUE(indices.empty());
+    cv::loadMesh(folder + fname, points_gold, indices_gold, normals_gold, colors_gold);
+    EXPECT_FALSE(points_gold.empty());
+    EXPECT_FALSE(indices_gold.empty());
 
-    cv::saveMesh(new_path, points, normals, indices);
-    EXPECT_TRUE(points.empty());
-    EXPECT_TRUE(normals.empty());
-    EXPECT_TRUE(indices.empty());
+    cv::saveMesh(new_path, points_gold, indices_gold, normals_gold, colors_gold);
 
+    std::vector<cv::Point3f> points, normals, colors;
+    std::vector<std::vector<int32_t>> indices;
+    cv::loadMesh(new_path, points, indices, normals, colors);
+
+    if (!normals.empty())
+    {
+        EXPECT_LE(cv::norm(normals_gold, normals, NORM_INF), 0);
+    }
+    EXPECT_LE(cv::norm(points_gold, points, NORM_INF), 0);
+    EXPECT_LE(cv::norm(colors_gold, colors, NORM_INF), 0);
+    EXPECT_EQ(indices_gold, indices);
     std::remove(new_path.c_str());
 }
 
+
+INSTANTIATE_TEST_CASE_P(PointCloud, PlyTest,
+    ::testing::Values("pointcloudio/orig.ply", "pointcloudio/orig_ascii_fidx.ply", "pointcloudio/orig_bin_fidx.ply",
+                      "pointcloudio/orig_ascii_vidx.ply", "pointcloudio/orig_bin.ply", "viz/dragon.ply"));
+
 TEST(PointCloud, NonexistentFile)
 {
     std::vector<cv::Point3f> points;

samples/python/point_cloud.py

@@ -15,7 +15,7 @@ cv.viz3d.setGridVisible("window", True)
 
 cv.waitKey(0)
 
-vertices, _, indices = cv.loadMesh("../data/teapot.obj")
+vertices, indices = cv.loadMesh("../data/teapot.obj")
 vertices = np.squeeze(vertices, axis=1)
 
 cv.viz3d.showMesh("window", "mesh", vertices, indices)