message: write alpha to PLY, despite meshlab and cloudcompare being incapable of visualizing it...
diff: @@ -82,6 +82,7 @@ bool outputMeshAsPly(const std::string& filename, const Mesh& mesh) {
  stream << "property uchar red" << std::endl;
  stream << "property uchar green" << std::endl;
  stream << "property uchar blue" << std::endl;
  + stream << "property uchar alpha" << std::endl;
  }
  if (mesh.hasTriangles()) {
  stream << "element face " << mesh.indices.size() / 3 << std::endl;
  @@ -101,8 +102,9 @@ bool outputMeshAsPly(const std::string& filename, const Mesh& mesh) {
  int r = static_cast<int>(color.r);
  int g = static_cast<int>(color.g);
  int b = static_cast<int>(color.b);
  + int a = static_cast<int>(color.a);
  // Uint8 prints as character otherwise. :(
  - stream << " " << r << " " << g << " " << b;
  + stream << " " << r << " " << g << " " << b << " " << a;
  }
  stream << std::endl;
  