Merge branch 'blender-v3.1-release'

Also fixed conflicts due to the change in file writing in the new obj exporter
in master, and fixed one of the tests that was added in master but not 3.1.

source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc

@@ -369,11 +369,25 @@ void OBJWriter::write_nurbs_curve(FormatHandler<eFileType::OBJ> &fh,
 
     /**
      * In `parm u 0 0.1 ..` line:, (total control points + 2) equidistant numbers in the
-     * parameter range are inserted.
+     * parameter range are inserted. However for curves with endpoint flag,
+     * first degree+1 numbers are zeroes, and last degree+1 numbers are ones
      */
+
+    const short flagsu = obj_nurbs_data.get_nurbs_flagu(spline_idx);
+    const bool cyclic = flagsu & CU_NURB_CYCLIC;
+    const bool endpoint = !cyclic && (flagsu & CU_NURB_ENDPOINT);
     fh.write<eOBJSyntaxElement::nurbs_parameter_begin>();
     for (int i = 1; i <= total_control_points + 2; i++) {
-      fh.write<eOBJSyntaxElement::nurbs_parameters>(1.0f * i / (total_control_points + 2 + 1));
+      float parm = 1.0f * i / (total_control_points + 2 + 1);
+      if (endpoint) {
+        if (i <= nurbs_degree) {
+          parm = 0;
+        }
+        else if (i > total_control_points + 2 - nurbs_degree) {
+          parm = 1;
+        }
+      }
+      fh.write<eOBJSyntaxElement::nurbs_parameters>(parm);
     }
     fh.write<eOBJSyntaxElement::nurbs_parameter_end>();
 

source/blender/io/wavefront_obj/exporter/obj_export_io.hh

@@ -177,7 +177,7 @@ constexpr FormattingSyntax syntax_elem_to_formatting(const eOBJSyntaxElement key
       return {"curv 0.0 1.0", 0, is_type_string_related<T...>};
     }
     case eOBJSyntaxElement::nurbs_parameter_begin: {
-      return {"parm 0.0", 0, is_type_string_related<T...>};
+      return {"parm u 0.0", 0, is_type_string_related<T...>};
     }
     case eOBJSyntaxElement::nurbs_parameters: {
       return {" %f", 1, is_type_float<T...>};

source/blender/io/wavefront_obj/exporter/obj_export_nurbs.cc

@@ -102,4 +102,10 @@ int OBJCurve::get_nurbs_degree(const int spline_index) const
   return nurb->orderu - 1;
 }
 
+short OBJCurve::get_nurbs_flagu(const int spline_index) const
+{
+  const Nurb *const nurb = static_cast<Nurb *>(BLI_findlink(&export_curve_->nurb, spline_index));
+  return nurb->flagu;
+}
+
 }  // namespace blender::io::obj

source/blender/io/wavefront_obj/exporter/obj_export_nurbs.hh

@@ -61,6 +61,10 @@ class OBJCurve : NonCopyable {
    * Get the degree of the NURBS spline at the given index.
    */
   int get_nurbs_degree(int spline_index) const;
+  /**
+   * Get the U flags (CU_NURB_*) of the NURBS spline at the given index.
+   */
+  short get_nurbs_flagu(int spline_index) const;
 
  private:
   /**

source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc

@@ -265,7 +265,7 @@ o abcdef
 o 012345678901234567890123456789abcd
 o 123
 curv 0.0 1.0
-parm 0.0
+parm u 0.0
 )";
   ASSERT_EQ(got_string, expected);
 }
@@ -410,6 +410,19 @@ TEST_F(obj_exporter_regression_test, nurbs_as_nurbs)
       "io_tests/blend_geometry/nurbs.blend", "io_tests/obj/nurbs.obj", "", _export.params);
 }
 
+TEST_F(obj_exporter_regression_test, nurbs_curves_as_nurbs)
+{
+  OBJExportParamsDefault _export;
+  _export.params.forward_axis = OBJ_AXIS_Y_FORWARD;
+  _export.params.up_axis = OBJ_AXIS_Z_UP;
+  _export.params.export_materials = false;
+  _export.params.export_curves_as_nurbs = true;
+  compare_obj_export_to_golden("io_tests/blend_geometry/nurbs_curves.blend",
+                               "io_tests/obj/nurbs_curves.obj",
+                               "",
+                               _export.params);
+}
+
 TEST_F(obj_exporter_regression_test, nurbs_as_mesh)
 {
   OBJExportParamsDefault _export;