proximity: Don't warn when parsing meshes with mtl files

bindings/pydrake/geometry_py.cc

@@ -1283,11 +1283,14 @@ void DoScalarIndependentDefinitions(py::module m) {
       py_rvp::reference_internal, py::arg("diffuse"),
       doc.MakePhongIllustrationProperties.doc);
 
-  m.def("ReadObjToSurfaceMesh",
-      py::overload_cast<const std::string&, double>(
-          &geometry::ReadObjToSurfaceMesh),
+  m.def(
+      "ReadObjToSurfaceMesh",
+      [](const std::string& filename, double scale) {
+        return geometry::ReadObjToSurfaceMesh(filename, scale);
+      },
       py::arg("filename"), py::arg("scale") = 1.0,
-      doc.ReadObjToSurfaceMesh.doc_2args_filename_scale);
+      // N.B. We have not bound the optional "on_warning" argument.
+      doc.ReadObjToSurfaceMesh.doc_3args);
 }
 
 void def_geometry(py::module m) {

geometry/proximity/obj_to_surface_mesh.cc

@@ -2,7 +2,9 @@
 
 #include <fstream>
 #include <istream>
+#include <memory>
 #include <numeric>
+#include <optional>
 #include <stdexcept>
 #include <string>
 #include <utility>
@@ -12,6 +14,7 @@
 #include <tiny_obj_loader.h>
 
 #include "drake/common/drake_assert.h"
+#include "drake/common/filesystem.h"
 #include "drake/common/text_logging.h"
 #include "drake/geometry/proximity/surface_mesh.h"
 
@@ -23,12 +26,6 @@ namespace {
 // TODO(DamrongGuoy): Refactor the tinyobj usage between here and
 //  ProximityEngine.
 
-// TODO(DamrongGuoy): Remove the guard DRAKE_DOXYGEN_CXX when we fixed
-//  issue#11130 "doxygen: Do not emit for `*.cc` files, also ignore
-//  `internal` namespace when appropriate".
-
-#ifndef DRAKE_DOXYGEN_CXX
-
 /*
  Converts vertices of tinyobj to vertices of SurfaceMesh.
  @param tinyobj_vertices
@@ -111,39 +108,36 @@ void TinyObjToSurfaceFaces(const tinyobj::mesh_t& mesh,
   }
 }
 
-#endif  // #ifndef DRAKE_DOXYGEN_CXX
-
-}  // namespace
-
-SurfaceMesh<double> ReadObjToSurfaceMesh(const std::string& filename,
-                                         const double scale) {
-  std::ifstream input_stream(filename);
-  if (!input_stream.is_open()) {
-    throw std::runtime_error("Cannot open file '" + filename +"'");
-  }
-  return ReadObjToSurfaceMesh(&input_stream, scale);
-}
-
-SurfaceMesh<double> ReadObjToSurfaceMesh(std::istream* input_stream,
-                                         const double scale) {
+SurfaceMesh<double> DoReadObjToSurfaceMesh(
+    std::istream* input_stream,
+    const double scale,
+    const std::optional<std::string>& mtl_base_dir,
+    const std::function<void(std::string_view)> on_warning) {
   tinyobj::attrib_t attrib;  // Used for vertices.
   std::vector<tinyobj::shape_t> shapes;  // Used for triangles.
   std::vector<tinyobj::material_t> materials;  // Not used.
   std::string warn;
   std::string err;
-  // Ignore material-library file.
-  tinyobj::MaterialReader* readMatFn = nullptr;
+  std::unique_ptr<tinyobj::MaterialReader> readMatFn;
+  if (mtl_base_dir) {
+    readMatFn = std::make_unique<tinyobj::MaterialFileReader>(*mtl_base_dir);
+  }
   // triangulate non-triangle faces.
   bool triangulate = true;
 
   bool ret = tinyobj::LoadObj(
-      &attrib, &shapes, &materials, &warn, &err, input_stream, readMatFn,
+      &attrib, &shapes, &materials, &warn, &err, input_stream, readMatFn.get(),
       triangulate);
   if (!ret || !err.empty()) {
     throw std::runtime_error("Error parsing Wavefront obj file : " + err);
   }
   if (!warn.empty()) {
-    drake::log()->warn("Warning parsing Wavefront obj file : {}", warn);
+    warn = "Warning parsing Wavefront obj file : " + warn;
+    if (on_warning) {
+      on_warning(warn);
+    } else {
+      drake::log()->warn("{}", warn);
+    }
   }
   if (shapes.size() == 0) {
     throw std::runtime_error("The Wavefront obj file has no faces.");
@@ -169,5 +163,28 @@ SurfaceMesh<double> ReadObjToSurfaceMesh(std::istream* input_stream,
   return SurfaceMesh<double>(std::move(faces), std::move(vertices));
 }
 
+}  // namespace
+
+SurfaceMesh<double> ReadObjToSurfaceMesh(
+    const std::string& filename,
+    const double scale,
+    std::function<void(std::string_view)> on_warning) {
+  std::ifstream input_stream(filename);
+  if (!input_stream.is_open()) {
+    throw std::runtime_error("Cannot open file '" + filename +"'");
+  }
+  const std::string mtl_base_dir =
+      filesystem::path(filename).parent_path().string() + "/";
+  return DoReadObjToSurfaceMesh(&input_stream, scale, mtl_base_dir,
+                                std::move(on_warning));
+}
+
+SurfaceMesh<double> ReadObjToSurfaceMesh(std::istream* input_stream,
+                                         const double scale) {
+  DRAKE_THROW_UNLESS(input_stream != nullptr);
+  return DoReadObjToSurfaceMesh(input_stream, scale,
+      std::nullopt /* mtl_base_dir */, {} /* on_warning*/);
+}
+
 }  // namespace geometry
 }  // namespace drake

geometry/proximity/obj_to_surface_mesh.h

@@ -2,6 +2,7 @@
 
 #include <istream>
 #include <string>
+#include <string_view>
 #include <vector>
 
 #include "drake/geometry/proximity/surface_mesh.h"
@@ -19,12 +20,17 @@ namespace geometry {
      A valid file name with absolute path or relative path.
  @param scale
      An optional scale to coordinates.
+ @param on_warning
+     An optional callback that will receive warning message(s) encountered
+     while reading the mesh.  When not provided, drake::log() will be used.
  @throws std::runtime_error if `filename` doesn't have a valid file path, or the
      file has no faces.
  @return surface mesh
  */
-SurfaceMesh<double> ReadObjToSurfaceMesh(const std::string& filename,
-                                         double scale = 1.0);
+SurfaceMesh<double> ReadObjToSurfaceMesh(
+    const std::string& filename,
+    double scale = 1.0,
+    std::function<void(std::string_view)> on_warning = {});
 
 /**
  Overload of @ref ReadObjToSurfaceMesh(const std::string&, double) with the

geometry/proximity/test/obj_to_surface_mesh_test.cc

@@ -76,7 +76,12 @@ GTEST_TEST(ObjToSurfaceMeshTest, TinyObjToSurfaceFaces) {
 GTEST_TEST(ObjToSurfaceMeshTest, ReadObjToSurfaceMesh) {
   const std::string filename =
       FindResourceOrThrow("drake/geometry/test/quad_cube.obj");
-  SurfaceMesh<double> surface = ReadObjToSurfaceMesh(filename);
+  const auto fail_on_warning = [](std::string_view message) {
+    throw std::runtime_error(fmt::format(
+        "Unexpected warning: {}", message));
+  };
+  SurfaceMesh<double> surface = ReadObjToSurfaceMesh(
+    filename, 1.0, fail_on_warning);
 
   ASSERT_EQ(surface.num_vertices(), 8);
   ASSERT_EQ(surface.num_faces(), 12);