[Bf-blender-cvs] [c24b2cdebf2] blender-v3.1-release: Fix T95360, new 3.1 obj exporter losing nurbs curve "endpoint".

[Aras Pranckevicius]

Commit: c24b2cdebf245a14f766c6f928b4326a5e4032ac
Author: Aras Pranckevicius
Date:   Sat Feb 5 17:51:03 2022 -0500
Branches: blender-v3.1-release
https://developer.blender.org/rBc24b2cdebf245a14f766c6f928b4326a5e4032ac

Fix T95360, new 3.1 obj exporter losing nurbs curve "endpoint".

The new wavefront .obj exporter in 3.1 was producing slightly invalid parm line syntax (missing u), and was not setting first/last N params to zeroes and ones for curves with "endpoint" flag properly.

===================================================================

M	source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
M	source/blender/io/wavefront_obj/exporter/obj_export_io.hh
M	source/blender/io/wavefront_obj/exporter/obj_export_nurbs.cc
M	source/blender/io/wavefront_obj/exporter/obj_export_nurbs.hh
M	source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc

===================================================================

diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
index d31353c4a76..38163af64b6 100644
--- a/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
+++ b/source/blender/io/wavefront_obj/exporter/obj_export_file_writer.cc
@@ -352,12 +352,24 @@ void OBJWriter::write_nurbs_curve(const OBJCurve &obj_nurbs_data) const
 
     /**
      * 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);
     file_handler_->write<eOBJSyntaxElement::nurbs_parameter_begin>();
     for (int i = 1; i <= total_control_points + 2; i++) {
-      file_handler_->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;
+        }
+      }
+      file_handler_->write<eOBJSyntaxElement::nurbs_parameters>(parm);
     }
     file_handler_->write<eOBJSyntaxElement::nurbs_parameter_end>();
 
diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_io.hh b/source/blender/io/wavefront_obj/exporter/obj_export_io.hh
index 1bbefaee75f..2eb2b66335d 100644
--- a/source/blender/io/wavefront_obj/exporter/obj_export_io.hh
+++ b/source/blender/io/wavefront_obj/exporter/obj_export_io.hh
@@ -168,7 +168,7 @@ 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...>};
diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_nurbs.cc b/source/blender/io/wavefront_obj/exporter/obj_export_nurbs.cc
index ec690115115..8a6d3b4b93a 100644
--- a/source/blender/io/wavefront_obj/exporter/obj_export_nurbs.cc
+++ b/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
diff --git a/source/blender/io/wavefront_obj/exporter/obj_export_nurbs.hh b/source/blender/io/wavefront_obj/exporter/obj_export_nurbs.hh
index 0c71c3cc09d..d831afec0a0 100644
--- a/source/blender/io/wavefront_obj/exporter/obj_export_nurbs.hh
+++ b/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:
   /**
diff --git a/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc b/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
index f97e2575aa2..ecae93f8f7a 100644
--- a/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
+++ b/source/blender/io/wavefront_obj/tests/obj_exporter_tests.cc
@@ -378,6 +378,17 @@ 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;