source/blender/io/usd/CMakeLists.txt

@@ -48,6 +48,7 @@ set(INC
   ../../blenkernel
   ../../blenlib
   ../../blenloader
+  ../../blentranslation
   ../../bmesh
   ../../depsgraph
   ../../editors/include
@@ -74,6 +75,7 @@ set(SRC
   intern/usd_hierarchy_iterator.cc
   intern/usd_writer_abstract.cc
   intern/usd_writer_camera.cc
+  intern/usd_writer_curves.cc
   intern/usd_writer_hair.cc
   intern/usd_writer_light.cc
   intern/usd_writer_material.cc
@@ -103,6 +105,7 @@ set(SRC
   intern/usd_hierarchy_iterator.h
   intern/usd_writer_abstract.h
   intern/usd_writer_camera.h
+  intern/usd_writer_curves.h
   intern/usd_writer_hair.h
   intern/usd_writer_light.h
   intern/usd_writer_material.h
@@ -159,6 +162,7 @@ if(WITH_GTESTS)
     tests/usd_tests_common.cc
     tests/usd_tests_common.h
     tests/usd_usdz_export_test.cc
+    tests/usd_curves_test.cc
     intern/usd_writer_material.h
   )
   if(USD_IMAGING_HEADERS)

source/blender/io/usd/intern/usd_hierarchy_iterator.cc

@@ -5,6 +5,7 @@
 #include "usd_hierarchy_iterator.h"
 #include "usd_writer_abstract.h"
 #include "usd_writer_camera.h"
+#include "usd_writer_curves.h"
 #include "usd_writer_hair.h"
 #include "usd_writer_light.h"
 #include "usd_writer_mesh.h"
@@ -12,6 +13,7 @@
 #include "usd_writer_transform.h"
 #include "usd_writer_volume.h"
 
+#include <memory>
 #include <string>
 
 #include <pxr/base/tf/stringUtils.h>
@@ -105,12 +107,14 @@ AbstractHierarchyWriter *USDHierarchyIterator::create_data_writer(const Hierarch
     case OB_MBALL:
       data_writer = new USDMetaballWriter(usd_export_context);
       break;
+    case OB_CURVES_LEGACY:
+    case OB_CURVES:
+      data_writer = new USDCurvesWriter(usd_export_context);
+      break;
     case OB_VOLUME:
       data_writer = new USDVolumeWriter(usd_export_context);
       break;
-
     case OB_EMPTY:
-    case OB_CURVES_LEGACY:
     case OB_SURF:
     case OB_FONT:
     case OB_SPEAKER:
@@ -119,7 +123,6 @@ AbstractHierarchyWriter *USDHierarchyIterator::create_data_writer(const Hierarch
     case OB_ARMATURE:
     case OB_GPENCIL_LEGACY:
     case OB_POINTCLOUD:
-    case OB_CURVES:
       return nullptr;
     case OB_TYPE_MAX:
       BLI_assert_msg(0, "OB_TYPE_MAX should not be used");

source/blender/io/usd/intern/usd_writer_curves.cc

@@ -0,0 +1,522 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2023 Blender Foundation. All rights reserved. */
+
+#include <numeric>
+
+#include <pxr/usd/usdGeom/basisCurves.h>
+#include <pxr/usd/usdGeom/curves.h>
+#include <pxr/usd/usdGeom/nurbsCurves.h>
+#include <pxr/usd/usdGeom/tokens.h>
+#include <pxr/usd/usdShade/material.h>
+#include <pxr/usd/usdShade/materialBindingAPI.h>
+
+#include "usd_hierarchy_iterator.h"
+#include "usd_writer_curves.h"
+
+#include "BKE_curve_legacy_convert.hh"
+#include "BKE_curves.hh"
+#include "BKE_lib_id.h"
+#include "BKE_material.h"
+
+#include "BLI_math_geom.h"
+#include "BLT_translation.h"
+
+#include "RNA_access.h"
+#include "RNA_enum_types.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+namespace blender::io::usd {
+
+USDCurvesWriter::USDCurvesWriter(const USDExporterContext &ctx) : USDAbstractWriter(ctx) {}
+
+USDCurvesWriter::~USDCurvesWriter() {}
+
+pxr::UsdGeomCurves USDCurvesWriter::DefineUsdGeomBasisCurves(pxr::VtValue curve_basis,
+                                                             const bool is_cyclic,
+                                                             const bool is_cubic)
+{
+  pxr::UsdGeomCurves curves = pxr::UsdGeomBasisCurves::Define(usd_export_context_.stage,
+                                                              usd_export_context_.usd_path);
+
+  pxr::UsdGeomBasisCurves basis_curves = pxr::UsdGeomBasisCurves(curves);
+  /* Not required to set the basis attribute for linear curves
+   * https://graphics.pixar.com/usd/dev/api/class_usd_geom_basis_curves.html#details */
+  if (is_cubic) {
+    basis_curves.CreateTypeAttr(pxr::VtValue(pxr::UsdGeomTokens->cubic));
+    basis_curves.CreateBasisAttr(curve_basis);
+  }
+  else {
+    basis_curves.CreateTypeAttr(pxr::VtValue(pxr::UsdGeomTokens->linear));
+  }
+
+  if (is_cyclic) {
+    basis_curves.CreateWrapAttr(pxr::VtValue(pxr::UsdGeomTokens->periodic));
+  }
+  else {
+    basis_curves.CreateWrapAttr(pxr::VtValue(pxr::UsdGeomTokens->nonperiodic));
+  }
+
+  return curves;
+}
+
+static void populate_curve_widths(const bke::CurvesGeometry &geometry, pxr::VtArray<float> &widths)
+{
+  const bke::AttributeAccessor curve_attributes = geometry.attributes();
+  const bke::AttributeReader<float> radii = curve_attributes.lookup<float>("radius",
+                                                                           ATTR_DOMAIN_POINT);
+
+  widths.resize(radii.varray.size());
+
+  for (const int i : radii.varray.index_range()) {
+    widths[i] = radii.varray[i] * 2.0f;
+  }
+}
+
+static pxr::TfToken get_curve_width_interpolation(const pxr::VtArray<float> &widths,
+                                                  const pxr::VtArray<int> &segments,
+                                                  const pxr::VtIntArray &control_point_counts,
+                                                  const bool is_cyclic)
+{
+  if (widths.empty()) {
+    return pxr::TfToken();
+  }
+
+  const size_t accumulated_control_point_count = std::accumulate(
+      control_point_counts.begin(), control_point_counts.end(), 0);
+
+  /* For Blender curves, radii are always stored per point. For linear curves, this should match
+   * with USD's vertex interpolation. For cubic curves, this should match with USD's varying
+   * interpolation. */
+  if (widths.size() == accumulated_control_point_count) {
+    return pxr::UsdGeomTokens->vertex;
+  }
+
+  size_t expectedVaryingSize = std::accumulate(segments.begin(), segments.end(), 0);
+  if (!is_cyclic) {
+    expectedVaryingSize += control_point_counts.size();
+  }
+
+  if (widths.size() == expectedVaryingSize) {
+    return pxr::UsdGeomTokens->varying;
+  }
+
+  WM_report(RPT_WARNING, "Curve width size not supported for USD interpolation");
+  return pxr::TfToken();
+}
+
+static void populate_curve_verts(const bke::CurvesGeometry &geometry,
+                                 const Span<float3> positions,
+                                 pxr::VtArray<pxr::GfVec3f> &verts,
+                                 pxr::VtIntArray &control_point_counts,
+                                 pxr::VtArray<int> &segments,
+                                 const bool is_cyclic,
+                                 const bool is_cubic)
+{
+  const OffsetIndices points_by_curve = geometry.points_by_curve();
+  for (const int i_curve : geometry.curves_range()) {
+
+    const IndexRange points = points_by_curve[i_curve];
+    for (const int i_point : points) {
+      verts.push_back(
+          pxr::GfVec3f(positions[i_point][0], positions[i_point][1], positions[i_point][2]));
+    }
+
+    const int tot_points = points.size();
+    control_point_counts[i_curve] = tot_points;
+
+    /* For periodic linear curve, segment count = curveVertexCount.
+     * For periodic cubic curve, segment count = curveVertexCount / vstep.
+     * For nonperiodic linear curve, segment count = curveVertexCount - 1.
+     * For nonperiodic cubic curve, segment count = ((curveVertexCount - 4) / vstep) + 1.
+     * This function handles linear and Catmull-Rom curves. For Catmull-Rom, vstep is 1.
+     * https://graphics.pixar.com/usd/dev/api/class_usd_geom_basis_curves.html */
+    if (is_cyclic) {
+      segments[i_curve] = tot_points;
+    }
+    else if (is_cubic) {
+      segments[i_curve] = (tot_points - 4) + 1;
+    }
+    else {
+      segments[i_curve] = tot_points - 1;
+    }
+  }
+}
+
+static void populate_curve_props(const bke::CurvesGeometry &geometry,
+                                 pxr::VtArray<pxr::GfVec3f> &verts,
+                                 pxr::VtIntArray &control_point_counts,
+                                 pxr::VtArray<float> &widths,
+                                 pxr::TfToken &interpolation,
+                                 const bool is_cyclic,
+                                 const bool is_cubic)
+{
+  const int num_curves = geometry.curve_num;
+  const Span<float3> positions = geometry.positions();
+
+  pxr::VtArray<int> segments(num_curves);
+
+  populate_curve_verts(
+      geometry, positions, verts, control_point_counts, segments, is_cyclic, is_cubic);
+
+  populate_curve_widths(geometry, widths);
+  interpolation = get_curve_width_interpolation(widths, segments, control_point_counts, is_cyclic);
+}
+
+static void populate_curve_verts_for_bezier(const bke::CurvesGeometry &geometry,
+                                            const Span<float3> positions,
+                                            const Span<float3> handles_l,
+                                            const Span<float3> handles_r,
+                                            pxr::VtArray<pxr::GfVec3f> &verts,
+                                            pxr::VtIntArray &control_point_counts,
+                                            pxr::VtArray<int> &segments,
+                                            const bool is_cyclic)
+{
+  const int bezier_vstep = 3;
+  const OffsetIndices points_by_curve = geometry.points_by_curve();
+
+  for (const int i_curve : geometry.curves_range()) {
+
+    const IndexRange points = points_by_curve[i_curve];
+    const int start_point_index = points[0];
+    const int last_point_index = points[points.size() - 1];
+
+    const int start_verts_count = verts.size();
+
+    for (int i_point = start_point_index; i_point < last_point_index; i_point++) {
+
+      /* The order verts in the USD bezier curve representation is [control point 0, right handle
+       * 0, left handle 1, control point 1, right handle 1, left handle 2, control point 2, ...].
+       * The last vert in the array doesn't need a right handle because the curve stops at that
+       * point. */
+      verts.push_back(
+          pxr::GfVec3f(positions[i_point][0], positions[i_point][1], positions[i_point][2]));
+
+      const blender::float3 right_handle = handles_r[i_point];
+      verts.push_back(pxr::GfVec3f(right_handle[0], right_handle[1], right_handle[2]));
+
+      const blender::float3 left_handle = handles_l[i_point + 1];
+      verts.push_back(pxr::GfVec3f(left_handle[0], left_handle[1], left_handle[2]));
+    }
+
+    verts.push_back(pxr::GfVec3f(positions[last_point_index][0],
+                                 positions[last_point_index][1],
+                                 positions[last_point_index][2]));
+
+    /* For USD representation of periodic bezier curve, one of the curve's points must be
+     * repeated to close the curve. The repeated point is the first point. Since the curve is
+     * closed, we now need to include the right handle of the last point and the left handle of
+     * the first point.
+     */
+    if (is_cyclic) {
+      const blender::float3 right_handle = handles_r[last_point_index];
+      verts.push_back(pxr::GfVec3f(right_handle[0], right_handle[1], right_handle[2]));
+
+      const blender::float3 left_handle = handles_l[start_point_index];
+      verts.push_back(pxr::GfVec3f(left_handle[0], left_handle[1], left_handle[2]));
+
+      verts.push_back(pxr::GfVec3f(positions[start_point_index][0],
+                                   positions[start_point_index][1],
+                                   positions[start_point_index][2]));
+    }
+
+    const int tot_points = verts.size() - start_verts_count;
+    control_point_counts[i_curve] = tot_points;
+
+    if (is_cyclic) {
+      segments[i_curve] = tot_points / bezier_vstep;
+    }
+    else {
+      segments[i_curve] = ((tot_points - 4) / bezier_vstep) + 1;
+    }
+  }
+}
+
+static void populate_curve_props_for_bezier(const bke::CurvesGeometry &geometry,
+                                            pxr::VtArray<pxr::GfVec3f> &verts,
+                                            pxr::VtIntArray &control_point_counts,
+                                            pxr::VtArray<float> &widths,
+                                            pxr::TfToken &interpolation,
+                                            const bool is_cyclic)
+{
+
+  const int num_curves = geometry.curve_num;
+
+  const Span<float3> positions = geometry.positions();
+
+  const Span<float3> handles_l = geometry.handle_positions_left();
+  const Span<float3> handles_r = geometry.handle_positions_right();
+
+  pxr::VtArray<int> segments(num_curves);
+
+  populate_curve_verts_for_bezier(
+      geometry, positions, handles_l, handles_r, verts, control_point_counts, segments, is_cyclic);
+
+  populate_curve_widths(geometry, widths);
+  interpolation = get_curve_width_interpolation(widths, segments, control_point_counts, is_cyclic);
+}
+
+static void populate_curve_props_for_nurbs(const bke::CurvesGeometry &geometry,
+                                           pxr::VtArray<pxr::GfVec3f> &verts,
+                                           pxr::VtIntArray &control_point_counts,
+                                           pxr::VtArray<float> &widths,
+                                           pxr::VtArray<double> &knots,
+                                           pxr::VtArray<int> &orders,
+                                           pxr::TfToken &interpolation,
+                                           const bool is_cyclic)
+{
+  /* Order and range, when representing a batched NurbsCurve should be authored one value per
+   * curve.*/
+  const int num_curves = geometry.curve_num;
+  orders.resize(num_curves);
+
+  const Span<float3> positions = geometry.positions();
+
+  VArray<int8_t> geom_orders = geometry.nurbs_orders();
+  VArray<int8_t> knots_modes = geometry.nurbs_knots_modes();
+
+  const OffsetIndices points_by_curve = geometry.points_by_curve();
+  for (const int i_curve : geometry.curves_range()) {
+    const IndexRange points = points_by_curve[i_curve];
+    for (const int i_point : points) {
+      verts.push_back(
+          pxr::GfVec3f(positions[i_point][0], positions[i_point][1], positions[i_point][2]));
+    }
+
+    const int tot_points = points.size();
+    control_point_counts[i_curve] = tot_points;
+
+    const int8_t order = geom_orders[i_curve];
+    orders[i_curve] = int(geom_orders[i_curve]);
+
+    const KnotsMode mode = KnotsMode(knots_modes[i_curve]);
+
+    const int knots_num = bke::curves::nurbs::knots_num(tot_points, order, is_cyclic);
+    Array<float> temp_knots(knots_num);
+    bke::curves::nurbs::calculate_knots(tot_points, mode, order, is_cyclic, temp_knots);
+
+    /* Knots should be the concatentation of all batched curves.
+     * https://graphics.pixar.com/usd/dev/api/class_usd_geom_nurbs_curves.html#details */
+    for (int i_knot = 0; i_knot < knots_num; i_knot++) {
+      knots.push_back(double(temp_knots[i_knot]));
+    }
+
+    /* For USD it is required to set specific end knots for periodic/non-periodic curves
+     * https://graphics.pixar.com/usd/dev/api/class_usd_geom_nurbs_curves.html#details */
+    int zeroth_knot_index = knots.size() - knots_num;
+    if (is_cyclic) {
+      knots[zeroth_knot_index] = knots[zeroth_knot_index + 1] -
+                                 (knots[knots.size() - 2] - knots[knots.size() - 3]);
+      knots[knots.size() - 1] = knots[knots.size() - 2] +
+                                (knots[zeroth_knot_index + 2] - knots[zeroth_knot_index + 1]);
+    }
+    else {
+      knots[zeroth_knot_index] = knots[zeroth_knot_index + 1];
+      knots[knots.size() - 1] = knots[knots.size() - 2];
+    }
+  }
+
+  populate_curve_widths(geometry, widths);
+  interpolation = pxr::UsdGeomTokens->vertex;
+}
+
+void USDCurvesWriter::set_writer_attributes_for_nurbs(const pxr::UsdGeomCurves usd_curves,
+                                                      const pxr::VtArray<double> knots,
+                                                      const pxr::VtArray<int> orders,
+                                                      const pxr::UsdTimeCode timecode)
+{
+  pxr::UsdAttribute attr_knots =
+      pxr::UsdGeomNurbsCurves(usd_curves).CreateKnotsAttr(pxr::VtValue(), true);
+  usd_value_writer_.SetAttribute(attr_knots, pxr::VtValue(knots), timecode);
+  pxr::UsdAttribute attr_order =
+      pxr::UsdGeomNurbsCurves(usd_curves).CreateOrderAttr(pxr::VtValue(), true);
+  usd_value_writer_.SetAttribute(attr_order, pxr::VtValue(orders), timecode);
+}
+
+void USDCurvesWriter::set_writer_attributes(pxr::UsdGeomCurves &usd_curves,
+                                            const pxr::VtArray<pxr::GfVec3f> verts,
+                                            const pxr::VtIntArray control_point_counts,
+                                            const pxr::VtArray<float> widths,
+                                            const pxr::UsdTimeCode timecode,
+                                            const pxr::TfToken interpolation)
+{
+  pxr::UsdAttribute attr_points = usd_curves.CreatePointsAttr(pxr::VtValue(), true);
+  usd_value_writer_.SetAttribute(attr_points, pxr::VtValue(verts), timecode);
+
+  pxr::UsdAttribute attr_vertex_counts = usd_curves.CreateCurveVertexCountsAttr(pxr::VtValue(),
+                                                                                true);
+  usd_value_writer_.SetAttribute(attr_vertex_counts, pxr::VtValue(control_point_counts), timecode);
+
+  if (widths.size() > 0) {
+    pxr::UsdAttribute attr_widths = usd_curves.CreateWidthsAttr(pxr::VtValue(), true);
+    usd_value_writer_.SetAttribute(attr_widths, pxr::VtValue(widths), timecode);
+
+    usd_curves.SetWidthsInterpolation(interpolation);
+  }
+}
+
+void USDCurvesWriter::do_write(HierarchyContext &context)
+{
+  Curves *curves;
+  std::unique_ptr<Curves, std::function<void(Curves *)>> converted_curves;
+
+  switch (context.object->type) {
+    case OB_CURVES_LEGACY: {
+      const Curve *legacy_curve = static_cast<Curve *>(context.object->data);
+      converted_curves = std::unique_ptr<Curves, std::function<void(Curves *)>>(
+          bke::curve_legacy_to_curves(*legacy_curve), [](Curves *c) { BKE_id_free(nullptr, c); });
+      curves = converted_curves.get();
+      break;
+    }
+    case OB_CURVES:
+      curves = static_cast<Curves *>(context.object->data);
+      break;
+    default:
+      BLI_assert_unreachable();
+      return;
+  }
+
+  const bke::CurvesGeometry &geometry = curves->geometry.wrap();
+  if (geometry.points_num() == 0) {
+    return;
+  }
+
+  const std::array<int, CURVE_TYPES_NUM> curve_type_counts = geometry.curve_type_counts();
+  const int number_of_curve_types = std::reduce(
+      curve_type_counts.begin(), curve_type_counts.end(), 0, [](int previous_result, int item) {
+        return item > 0 ? ++previous_result : previous_result;
+      });
+
+  if (number_of_curve_types > 1) {
+    WM_report(RPT_WARNING, "Cannot export mixed curve types in the same Curves object");
+    return;
+  }
+
+  const VArray<bool> cyclic_values = geometry.cyclic();
+  const bool is_cyclic = cyclic_values[0];
+  bool all_same_cyclic_type = true;
+
+  for (const int i : cyclic_values.index_range()) {
+    if (cyclic_values[i] != is_cyclic) {
+      all_same_cyclic_type = false;
+      break;
+    }
+  }
+
+  if (!all_same_cyclic_type) {
+    WM_report(RPT_WARNING,
+              "Cannot export mixed cyclic and non-cyclic curves in the same Curves object");
+    return;
+  }
+
+  const pxr::UsdTimeCode timecode = get_export_time_code();
+  pxr::UsdGeomCurves usd_curves;
+
+  pxr::VtArray<pxr::GfVec3f> verts;
+  pxr::VtIntArray control_point_counts;
+  control_point_counts.resize(geometry.curves_num());
+  pxr::VtArray<float> widths;
+  pxr::TfToken interpolation;
+
+  const int8_t curve_type = geometry.curve_types()[0];
+
+  if (first_frame_curve_type == -1) {
+    first_frame_curve_type = curve_type;
+  }
+  else if (first_frame_curve_type != curve_type) {
+    const char *first_frame_curve_type_name = nullptr;
+    RNA_enum_name_from_value(
+        rna_enum_curves_types, int(first_frame_curve_type), &first_frame_curve_type_name);
+
+    const char *current_curve_type_name = nullptr;
+    RNA_enum_name_from_value(rna_enum_curves_types, int(curve_type), &current_curve_type_name);
+
+    WM_reportf(RPT_WARNING,
+               "USD does not support animating curve types. The curve type changes from %s to "
+               "%s on frame %f",
+               IFACE_(first_frame_curve_type_name),
+               IFACE_(current_curve_type_name),
+               timecode);
+    return;
+  }
+
+  switch (curve_type) {
+    case CURVE_TYPE_POLY:
+      usd_curves = DefineUsdGeomBasisCurves(pxr::VtValue(), is_cyclic, false);
+
+      populate_curve_props(
+          geometry, verts, control_point_counts, widths, interpolation, is_cyclic, false);
+      break;
+    case CURVE_TYPE_CATMULL_ROM:
+      usd_curves = DefineUsdGeomBasisCurves(
+          pxr::VtValue(pxr::UsdGeomTokens->catmullRom), is_cyclic, true);
+
+      populate_curve_props(
+          geometry, verts, control_point_counts, widths, interpolation, is_cyclic, true);
+      break;
+    case CURVE_TYPE_BEZIER:
+      usd_curves = DefineUsdGeomBasisCurves(
+          pxr::VtValue(pxr::UsdGeomTokens->bezier), is_cyclic, true);
+
+      populate_curve_props_for_bezier(
+          geometry, verts, control_point_counts, widths, interpolation, is_cyclic);
+      break;
+    case CURVE_TYPE_NURBS: {
+      pxr::VtArray<double> knots;
+      pxr::VtArray<int> orders;
+      orders.resize(geometry.curves_num());
+
+      usd_curves = pxr::UsdGeomNurbsCurves::Define(usd_export_context_.stage,
+                                                   usd_export_context_.usd_path);
+
+      populate_curve_props_for_nurbs(
+          geometry, verts, control_point_counts, widths, knots, orders, interpolation, is_cyclic);
+
+      set_writer_attributes_for_nurbs(usd_curves, knots, orders, timecode);
+
+      break;
+    }
+    default:
+      BLI_assert_unreachable();
+  }
+
+  set_writer_attributes(usd_curves, verts, control_point_counts, widths, timecode, interpolation);
+
+  assign_materials(context, usd_curves);
+}
+
+void USDCurvesWriter::assign_materials(const HierarchyContext &context,
+                                       pxr::UsdGeomCurves usd_curve)
+{
+  if (context.object->totcol == 0) {
+    return;
+  }
+
+  bool curve_material_bound = false;
+  for (short mat_num = 0; mat_num < context.object->totcol; mat_num++) {
+    Material *material = BKE_object_material_get(context.object, mat_num + 1);
+    if (material == nullptr) {
+      continue;
+    }
+
+    pxr::UsdShadeMaterialBindingAPI api = pxr::UsdShadeMaterialBindingAPI(usd_curve.GetPrim());
+    pxr::UsdShadeMaterial usd_material = ensure_usd_material(context, material);
+    api.Bind(usd_material);
+
+    /* USD seems to support neither per-material nor per-face-group double-sidedness, so we just
+     * use the flag from the first non-empty material slot. */
+    usd_curve.CreateDoubleSidedAttr(
+        pxr::VtValue((material->blend_flag & MA_BL_CULL_BACKFACE) == 0));
+
+    curve_material_bound = true;
+    break;
+  }
+
+  if (!curve_material_bound) {
+    /* Blender defaults to double-sided, but USD to single-sided. */
+    usd_curve.CreateDoubleSidedAttr(pxr::VtValue(true));
+  }
+}
+
+}  // namespace blender::io::usd

source/blender/io/usd/intern/usd_writer_curves.h

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2022 Blender Foundation. All rights reserved. */
+#pragma once
+
+#include <memory>
+
+#include "DNA_curves_types.h"
+#include "usd_writer_abstract.h"
+
+#include <pxr/usd/usdGeom/basisCurves.h>
+
+namespace blender::io::usd {
+
+/* Writer for writing Curves data as USD curves. */
+class USDCurvesWriter : public USDAbstractWriter {
+ public:
+  USDCurvesWriter(const USDExporterContext &ctx);
+  ~USDCurvesWriter();
+
+ protected:
+  virtual void do_write(HierarchyContext &context) override;
+  void assign_materials(const HierarchyContext &context, pxr::UsdGeomCurves usd_curve);
+
+ private:
+  int8_t first_frame_curve_type = -1;
+  pxr::UsdGeomCurves DefineUsdGeomBasisCurves(pxr::VtValue curve_basis, bool cyclic, bool cubic);
+
+  void set_writer_attributes(pxr::UsdGeomCurves &usd_curves,
+                             const pxr::VtArray<pxr::GfVec3f> verts,
+                             const pxr::VtIntArray control_point_counts,
+                             const pxr::VtArray<float> widths,
+                             const pxr::UsdTimeCode timecode,
+                             const pxr::TfToken interpolation);
+
+  void set_writer_attributes_for_nurbs(const pxr::UsdGeomCurves usd_curves,
+                                       const pxr::VtArray<double> knots,
+                                       const pxr::VtArray<int> orders,
+                                       const pxr::UsdTimeCode timecode);
+};
+
+}  // namespace blender::io::usd

source/blender/io/usd/tests/usd_curves_test.cc

@@ -0,0 +1,350 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "testing/testing.h"
+#include "tests/blendfile_loading_base_test.h"
+
+#include <pxr/base/plug/registry.h>
+#include <pxr/base/tf/stringUtils.h>
+#include <pxr/base/vt/types.h>
+#include <pxr/base/vt/value.h>
+#include <pxr/usd/sdf/types.h>
+#include <pxr/usd/usd/object.h>
+#include <pxr/usd/usd/prim.h>
+#include <pxr/usd/usd/stage.h>
+#include <pxr/usd/usdGeom/basisCurves.h>
+#include <pxr/usd/usdGeom/curves.h>
+#include <pxr/usd/usdGeom/mesh.h>
+#include <pxr/usd/usdGeom/nurbsCurves.h>
+#include <pxr/usd/usdGeom/subset.h>
+#include <pxr/usd/usdGeom/tokens.h>
+
+#include "DNA_material_types.h"
+#include "DNA_node_types.h"
+
+#include "BKE_context.h"
+#include "BKE_lib_id.h"
+#include "BKE_main.h"
+#include "BKE_mesh.h"
+#include "BKE_node.h"
+#include "BLI_fileops.h"
+#include "BLI_math.h"
+#include "BLI_math_vector_types.hh"
+#include "BLI_path_util.h"
+#include "BLO_readfile.h"
+
+#include "BKE_node_runtime.hh"
+
+#include "DEG_depsgraph.h"
+
+#include "WM_api.h"
+
+#include "usd.h"
+#include "usd_tests_common.h"
+
+namespace blender::io::usd {
+
+const StringRefNull usd_curves_test_filename = "usd/usd_curves_test.blend";
+const StringRefNull output_filename = "usd/output.usda";
+
+static void check_catmullRom_curve(const pxr::UsdPrim prim,
+                                   const bool is_periodic,
+                                   const int vertex_count);
+static void check_bezier_curve(const pxr::UsdPrim bezier_prim,
+                               const bool is_periodic,
+                               const int vertex_count);
+static void check_nurbs_curve(const pxr::UsdPrim nurbs_prim,
+                              const int vertex_count,
+                              const int knots_count,
+                              const int order);
+static void check_nurbs_circle(const pxr::UsdPrim nurbs_prim,
+                               const int vertex_count,
+                               const int knots_count,
+                               const int order);
+
+class UsdCurvesTest : public BlendfileLoadingBaseTest {
+ protected:
+  struct bContext *context = nullptr;
+
+ public:
+  bool load_file_and_depsgraph(const StringRefNull &filepath,
+                               const eEvaluationMode eval_mode = DAG_EVAL_VIEWPORT)
+  {
+    if (!blendfile_load(filepath.c_str())) {
+      return false;
+    }
+    depsgraph_create(eval_mode);
+
+    context = CTX_create();
+    CTX_data_main_set(context, bfile->main);
+    CTX_data_scene_set(context, bfile->curscene);
+
+    return true;
+  }
+
+  virtual void SetUp() override
+  {
+    BlendfileLoadingBaseTest::SetUp();
+    std::string usd_plugin_path = register_usd_plugins_for_tests();
+    if (usd_plugin_path.empty()) {
+      FAIL();
+    }
+  }
+
+  virtual void TearDown() override
+  {
+    BlendfileLoadingBaseTest::TearDown();
+    CTX_free(context);
+    context = nullptr;
+
+    if (BLI_exists(output_filename.c_str())) {
+      BLI_delete(output_filename.c_str(), false, false);
+    }
+  }
+};
+
+TEST_F(UsdCurvesTest, usd_export_curves)
+{
+  if (!load_file_and_depsgraph(usd_curves_test_filename)) {
+    ADD_FAILURE();
+    return;
+  }
+
+  /* File sanity check. */
+  EXPECT_EQ(BLI_listbase_count(&bfile->main->objects), 6);
+
+  USDExportParams params{};
+
+  const bool result = USD_export(context, output_filename.c_str(), &params, false);
+  EXPECT_TRUE(result) << "USD export should succed.";
+
+  pxr::UsdStageRefPtr stage = pxr::UsdStage::Open(output_filename);
+  ASSERT_NE(stage, nullptr) << "Stage should not be null after opening usd file.";
+
+  {
+    std::string prim_name = pxr::TfMakeValidIdentifier("BezierCurve");
+    pxr::UsdPrim test_prim = stage->GetPrimAtPath(pxr::SdfPath("/BezierCurve/" + prim_name));
+    EXPECT_TRUE(test_prim.IsValid());
+    check_bezier_curve(test_prim, false, 7);
+  }
+
+  {
+    std::string prim_name = pxr::TfMakeValidIdentifier("BezierCircle");
+    pxr::UsdPrim test_prim = stage->GetPrimAtPath(pxr::SdfPath("/BezierCircle/" + prim_name));
+    EXPECT_TRUE(test_prim.IsValid());
+    check_bezier_curve(test_prim, true, 13);
+  }
+
+  {
+    std::string prim_name = pxr::TfMakeValidIdentifier("NurbsCurve");
+    pxr::UsdPrim test_prim = stage->GetPrimAtPath(pxr::SdfPath("/NurbsCurve/" + prim_name));
+    EXPECT_TRUE(test_prim.IsValid());
+    check_nurbs_curve(test_prim, 6, 20, 4);
+  }
+
+  {
+    std::string prim_name = pxr::TfMakeValidIdentifier("NurbsCircle");
+    pxr::UsdPrim test_prim = stage->GetPrimAtPath(pxr::SdfPath("/NurbsCircle/" + prim_name));
+    EXPECT_TRUE(test_prim.IsValid());
+    check_nurbs_circle(test_prim, 8, 13, 3);
+  }
+
+  {
+    std::string prim_name = pxr::TfMakeValidIdentifier("Curves");
+    pxr::UsdPrim test_prim = stage->GetPrimAtPath(pxr::SdfPath("/Cube/Curves/" + prim_name));
+    EXPECT_TRUE(test_prim.IsValid());
+    check_catmullRom_curve(test_prim, false, 8);
+  }
+}
+
+/**
+ * Test that the provided prim is a valid catmullRom curve. We also check it matches the expected
+ * wrap type, and has the expected number of vertices.
+ */
+static void check_catmullRom_curve(const pxr::UsdPrim prim,
+                                   const bool is_periodic,
+                                   const int vertex_count)
+{
+  auto curve = pxr::UsdGeomBasisCurves(prim);
+
+  pxr::VtValue basis;
+  pxr::UsdAttribute basis_attr = curve.GetBasisAttr();
+  basis_attr.Get(&basis);
+  auto basis_token = basis.Get<pxr::TfToken>();
+
+  EXPECT_EQ(basis_token, pxr::UsdGeomTokens->catmullRom)
+      << "Basis token should be catmullRom for catmullRom curve";
+
+  pxr::VtValue type;
+  pxr::UsdAttribute type_attr = curve.GetTypeAttr();
+  type_attr.Get(&type);
+  auto type_token = type.Get<pxr::TfToken>();
+
+  EXPECT_EQ(type_token, pxr::UsdGeomTokens->cubic)
+      << "Type token should be cubic for catmullRom curve";
+
+  pxr::VtValue wrap;
+  pxr::UsdAttribute wrap_attr = curve.GetWrapAttr();
+  wrap_attr.Get(&wrap);
+  auto wrap_token = wrap.Get<pxr::TfToken>();
+
+  if (is_periodic) {
+    EXPECT_EQ(wrap_token, pxr::UsdGeomTokens->periodic)
+        << "Wrap token should be periodic for periodic curve";
+  }
+  else {
+    EXPECT_EQ(wrap_token, pxr::UsdGeomTokens->nonperiodic)
+        << "Wrap token should be nonperiodic for nonperiodic curve";
+  }
+
+  pxr::UsdAttribute vert_count_attr = curve.GetCurveVertexCountsAttr();
+  pxr::VtArray<int> vert_counts;
+  vert_count_attr.Get(&vert_counts);
+
+  EXPECT_EQ(vert_counts.size(), 3) << "Prim should contain verts for three curves";
+  EXPECT_EQ(vert_counts[0], vertex_count) << "Curve 0 should have " << vertex_count << " verts.";
+  EXPECT_EQ(vert_counts[1], vertex_count) << "Curve 1 should have " << vertex_count << " verts.";
+  EXPECT_EQ(vert_counts[2], vertex_count) << "Curve 2 should have " << vertex_count << " verts.";
+}
+
+/**
+ * Test that the provided prim is a valid bezier curve. We also check it matches the expected
+ * wrap type, and has the expected number of vertices.
+ */
+static void check_bezier_curve(const pxr::UsdPrim bezier_prim,
+                               const bool is_periodic,
+                               const int vertex_count)
+{
+  auto curve = pxr::UsdGeomBasisCurves(bezier_prim);
+
+  pxr::VtValue basis;
+  pxr::UsdAttribute basis_attr = curve.GetBasisAttr();
+  basis_attr.Get(&basis);
+  auto basis_token = basis.Get<pxr::TfToken>();
+
+  EXPECT_EQ(basis_token, pxr::UsdGeomTokens->bezier)
+      << "Basis token should be bezier for bezier curve";
+
+  pxr::VtValue type;
+  pxr::UsdAttribute type_attr = curve.GetTypeAttr();
+  type_attr.Get(&type);
+  auto type_token = type.Get<pxr::TfToken>();
+
+  EXPECT_EQ(type_token, pxr::UsdGeomTokens->cubic)
+      << "Type token should be cubic for bezier curve";
+
+  pxr::VtValue wrap;
+  pxr::UsdAttribute wrap_attr = curve.GetWrapAttr();
+  wrap_attr.Get(&wrap);
+  auto wrap_token = wrap.Get<pxr::TfToken>();
+
+  if (is_periodic) {
+    EXPECT_EQ(wrap_token, pxr::UsdGeomTokens->periodic)
+        << "Wrap token should be periodic for periodic curve";
+  }
+  else {
+    EXPECT_EQ(wrap_token, pxr::UsdGeomTokens->nonperiodic)
+        << "Wrap token should be nonperiodic for nonperiodic curve";
+  }
+
+  auto widths_interp_token = curve.GetWidthsInterpolation();
+  EXPECT_EQ(widths_interp_token, pxr::UsdGeomTokens->varying)
+      << "Widths interpolation token should be varying for bezier curve";
+
+  pxr::UsdAttribute vert_count_attr = curve.GetCurveVertexCountsAttr();
+  pxr::VtArray<int> vert_counts;
+  vert_count_attr.Get(&vert_counts);
+
+  EXPECT_EQ(vert_counts.size(), 1) << "Prim should only contains verts for a single curve";
+  EXPECT_EQ(vert_counts[0], vertex_count) << "Curve should have " << vertex_count << " verts.";
+}
+
+/**
+ * Test that the provided prim is a valid NURBS curve. We also check it matches the expected
+ * wrap type, and has the expected number of vertices. For NURBS, we also validate that the knots
+ * layout matches the expected layout for periodic/non-periodic curves according to the USD spec.
+ */
+static void check_nurbs_curve(const pxr::UsdPrim nurbs_prim,
+                              const int vertex_count,
+                              const int knots_count,
+                              const int order)
+{
+  auto curve = pxr::UsdGeomNurbsCurves(nurbs_prim);
+
+  pxr::UsdAttribute order_attr = curve.GetOrderAttr();
+  pxr::VtArray<int> orders;
+  order_attr.Get(&orders);
+
+  EXPECT_EQ(orders.size(), 2) << "Prim should contain orders for two curves";
+  EXPECT_EQ(orders[0], order) << "Curves should have order " << order;
+  EXPECT_EQ(orders[1], order) << "Curves should have order " << order;
+
+  pxr::UsdAttribute knots_attr = curve.GetKnotsAttr();
+  pxr::VtArray<double> knots;
+  knots_attr.Get(&knots);
+
+  EXPECT_EQ(knots.size(), knots_count) << "Curve should have " << knots_count << " knots.";
+  for (int i = 0; i < 2; i++) {
+    int zeroth_knot_index = i * (knots_count / 2);
+
+    EXPECT_EQ(knots[zeroth_knot_index], knots[zeroth_knot_index + 1])
+        << "NURBS curve should satisfy this knots rule for a nonperiodic curve";
+    EXPECT_EQ(knots[knots.size() - 1], knots[knots.size() - 2])
+        << "NURBS curve should satisfy this knots rule for a nonperiodic curve";
+  }
+
+  auto widths_interp_token = curve.GetWidthsInterpolation();
+  EXPECT_EQ(widths_interp_token, pxr::UsdGeomTokens->vertex)
+      << "Widths interpolation token should be vertex for NURBS curve";
+
+  pxr::UsdAttribute vert_count_attr = curve.GetCurveVertexCountsAttr();
+  pxr::VtArray<int> vert_counts;
+  vert_count_attr.Get(&vert_counts);
+
+  EXPECT_EQ(vert_counts.size(), 2) << "Prim should contain verts for two curves";
+  EXPECT_EQ(vert_counts[0], vertex_count) << "Curve should have " << vertex_count << " verts.";
+  EXPECT_EQ(vert_counts[1], vertex_count) << "Curve should have " << vertex_count << " verts.";
+}
+
+/**
+ * Test that the provided prim is a valid NURBS curve. We also check it matches the expected
+ * wrap type, and has the expected number of vertices. For NURBS, we also validate that the knots
+ * layout matches the expected layout for periodic/non-periodic curves according to the USD spec.
+ */
+static void check_nurbs_circle(const pxr::UsdPrim nurbs_prim,
+                               const int vertex_count,
+                               const int knots_count,
+                               const int order)
+{
+  auto curve = pxr::UsdGeomNurbsCurves(nurbs_prim);
+
+  pxr::UsdAttribute order_attr = curve.GetOrderAttr();
+  pxr::VtArray<int> orders;
+  order_attr.Get(&orders);
+
+  EXPECT_EQ(orders.size(), 1) << "Prim should contain orders for one curves";
+  EXPECT_EQ(orders[0], order) << "Curve should have order " << order;
+
+  pxr::UsdAttribute knots_attr = curve.GetKnotsAttr();
+  pxr::VtArray<double> knots;
+  knots_attr.Get(&knots);
+
+  EXPECT_EQ(knots.size(), knots_count) << "Curve should have " << knots_count << " knots.";
+
+  EXPECT_EQ(knots[0], knots[1] - (knots[knots.size() - 2] - knots[knots.size() - 3]))
+      << "NURBS curve should satisfy this knots rule for a periodic curve";
+  EXPECT_EQ(knots[knots.size() - 1], knots[knots.size() - 2] + (knots[2] - knots[1]))
+      << "NURBS curve should satisfy this knots rule for a periodic curve";
+
+  auto widths_interp_token = curve.GetWidthsInterpolation();
+  EXPECT_EQ(widths_interp_token, pxr::UsdGeomTokens->vertex)
+      << "Widths interpolation token should be vertex for NURBS curve";
+
+  pxr::UsdAttribute vert_count_attr = curve.GetCurveVertexCountsAttr();
+  pxr::VtArray<int> vert_counts;
+  vert_count_attr.Get(&vert_counts);
+
+  EXPECT_EQ(vert_counts.size(), 1) << "Prim should contain verts for one curve";
+  EXPECT_EQ(vert_counts[0], vertex_count) << "Curve should have " << vertex_count << " verts.";
+}
+
+}  // namespace blender::io::usd