add SPLAT decoder to be able to encode .splat files to .drc files

src/draco/io/point_cloud_io.cc

@@ -18,6 +18,7 @@
 #include "draco/io/obj_decoder.h"
 #include "draco/io/parser_utils.h"
 #include "draco/io/ply_decoder.h"
+#include "draco/io/splat_decoder.cc"
 
 namespace draco {
 
@@ -26,7 +27,7 @@ StatusOr<std::unique_ptr<PointCloud>> ReadPointCloudFromFile(
   std::unique_ptr<PointCloud> pc(new PointCloud());
   // Analyze file extension.
   const std::string extension = parser::ToLower(
-      file_name.size() >= 4 ? file_name.substr(file_name.size() - 4)
+      file_name.size() >= 5 ? file_name.substr(file_name.find_last_of('.'))
                             : file_name);
   if (extension == ".obj") {
     // Wavefront OBJ file format.
@@ -43,6 +44,12 @@ StatusOr<std::unique_ptr<PointCloud>> ReadPointCloudFromFile(
     DRACO_RETURN_IF_ERROR(ply_decoder.DecodeFromFile(file_name, pc.get()));
     return std::move(pc);
   }
+  if (extension == ".splat") {
+    // SPLAT file format.
+    SplatDecoder splat_decoder;
+    DRACO_RETURN_IF_ERROR(splat_decoder.ReadSplatFile(file_name, pc.get()));
+    return std::move(pc);
+  }
 
   std::vector<char> buffer;
   if (!ReadFileToBuffer(file_name, &buffer)) {

src/draco/io/splat_decoder.cc

@@ -0,0 +1,78 @@
+// Copyright 2025 Patrick Trollmann.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#include "draco/io/splat_decoder.h"
+
+namespace draco {
+SplatDecoder::SplatDecoder() {}
+
+Status SplatDecoder::ReadSplatFile(const std::string &filename,
+                         PointCloud *out_point_cloud) {
+  std::ifstream file(filename, std::ios::binary);
+  if (!file) {
+    return Status(Status::DRACO_ERROR, "Unable to open input file.");
+  }
+
+  struct Gaussian {
+    float position[3];
+    float scale[3];
+    uint8_t color[4];
+    uint8_t rotation[4];
+  };
+
+  std::vector<Gaussian> gaussians;
+  Gaussian gaussian;
+  while (file.read(reinterpret_cast<char *>(&gaussian), sizeof(Gaussian))) {
+    gaussians.push_back(gaussian);
+  }
+  const PointIndex::ValueType num_vertices = gaussians.size();
+  out_point_cloud->set_num_points(num_vertices);
+
+  GeometryAttribute vapos;
+  vapos.Init(GeometryAttribute::POSITION, nullptr, 6, DT_FLOAT32, false,
+             sizeof(float) * 6, 0);
+  const int att_id_position =
+      out_point_cloud->AddAttribute(vapos, true, num_vertices);
+
+  GeometryAttribute vacol;
+  vacol.Init(GeometryAttribute::COLOR, nullptr, 8, DT_UINT8, true,
+             sizeof(uint8_t) * 8, 0);
+  const int att_id_color =
+      out_point_cloud->AddAttribute(vacol, true, num_vertices);
+
+  for (PointIndex::ValueType i = 0; i < num_vertices; ++i) {
+    const auto &g = gaussians[i];
+    std::array<float, 6> valpos;
+    valpos[0] = g.position[0];
+    valpos[1] = g.position[1];
+    valpos[2] = g.position[2];    
+    valpos[3] = g.scale[0];
+    valpos[4] = g.scale[1];
+    valpos[5] = g.scale[2];
+    out_point_cloud->attribute(att_id_position)
+        ->SetAttributeValue(AttributeValueIndex(i), &valpos[0]);
+
+    std::array<uint8_t, 8> valcol;
+    for (int j = 0; j < 4; j++) {
+      valcol[j] = g.color[j];
+    }
+    for (int j = 4; j < 8; j++) {
+      valcol[j] = g.rotation[j-4];
+    }
+    out_point_cloud->attribute(att_id_color)
+        ->SetAttributeValue(AttributeValueIndex(i), &valcol[0]);
+  }
+  return OkStatus();
+}
+}  // namespace draco

src/draco/io/splat_decoder.h

@@ -0,0 +1,44 @@
+// Copyright 2025 Patrick Trollmann.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+#ifndef DRACO_IO_SPLAT_DECODER_H_
+#define DRACO_IO_SPLAT_DECODER_H_
+
+#include <fstream>
+#include <vector>
+
+#include "draco/point_cloud/point_cloud.h"
+#include "draco/core/status.h"
+
+namespace draco {
+
+// Decodes a SPLAT file into draco::PointCloud.
+// The current implementation assumes the properties: POSITION, SCALE, COLOR, ROTATION.
+// POSITION and SCALE are stored together as GeometryAttribute.POSITION. COLOR and ROATION
+// are stored together as GeometryAttribute.COLOR. Currently, it is not possible to use 
+// custom GeometryAttribute types or the GENERIC type. This types cannot be decoded in
+// the WebGL version of Draco.
+class SplatDecoder {
+ public:
+  SplatDecoder();
+
+  // Decodes a splat file stored in the input file.
+  Status ReadSplatFile(const std::string &filename,
+                       PointCloud *out_point_cloud);
+
+};
+
+}  // namespace draco
+
+#endif  // DRACO_IO_SPLAT_DECODER_H_