Add type-erased helper class PrimValue.

CMakeLists.txt

@@ -56,6 +56,7 @@ endif()
 
 set(TINYUSDZ_SOURCES
     ${PROJECT_SOURCE_DIR}/src/tinyusdz.cc
+    ${PROJECT_SOURCE_DIR}/src/usda-writer.cc
     )
 
 set(TINYUSDZ_DEP_SOURCES

README.md

@@ -150,6 +150,7 @@ See [prim_format.md](doc/prim_format.md) and [preview_surface.md](doc/preview_su
 
 ## TODO
 
+* [ ] Support Crate(binary) version 0.8.0(USD v20.11 default)
 * [ ] Write parser based on the schema definition.
 * [ ] Subdivision surface using OpenSubdiv.
   * [ ] Replace OpenSubdiv with our own subdiv library or embree3's one.

doc/TODO.md

@@ -0,0 +1,24 @@
+# USDC parser
+
+Base implementation in TinyUSDZ: v0.7.0
+
+* [ ] v0.8.0 support
+  * [ ] PayloadListOp/Payload + layer offsets
+  * [ ] LayerOffset
+* [ ] v0.9.0 support
+  * [ ] TimeCode, TimeCode[]
+
+# USDA parser
+
+* [ ] USDA parser
+
+# USDC writer
+
+* [ ] USDC writer
+
+# USDA writer
+
+* [ ] USDA writer
+
+
+EoL.

doc/usdc_format.md

@@ -7,6 +7,20 @@
 
 => total 88 bytes
 
+## Version
+
+From pxr/usd/usd/crateFile.cpp
+
+```
+// Version history:
+// 0.9.0: Added support for the timecode and timecode[] value types.
+// 0.8.0: Added support for SdfPayloadListOp values and SdfPayload values with
+//        layer offsets.
+// 0.7.0: Array sizes written as 64 bit ints.
+```
+
+* 0.8.0(USD v20.11)
+  
 ## Compression
 
 version 0.4.0 or later uses LZ4 for compression and interger compression(pxr original? compression. its backend still uses LZ4) for index arrays.

src/tinyusdz.hh

@@ -44,6 +44,10 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 namespace tinyusdz {
 
+constexpr int version_major = 0;
+constexpr int version_minor = 7;
+constexpr int version_micro = 0;
+
 // Simple image class.
 // No colorspace conversion will be applied when decoding image data(e.g. from
 // .jpg, .png).
@@ -433,6 +437,30 @@ class Path {
   bool valid{false};
 };
 
+class TimeCode {
+  TimeCode(double tm = 0.0) : _time(tm) {}
+
+  size_t hash() const { return std::hash<double>{}(_time); }
+
+  double value() const { return _time; }
+
+ private:
+  double _time;
+};
+
+class LayerOffset {
+ private:
+  double _offset;
+  double _scale;
+};
+
+class Payload {
+ private:
+  std::string _asset_path;
+  Path _prim_path;
+  LayerOffset _layer_offset;
+};
+
 enum ValueTypeId {
   VALUE_TYPE_INVALID = 0,
 
@@ -585,6 +613,99 @@ struct TimeSamples {
   std::vector<Value> values;
 };
 
+///
+/// Simple type-erased primitive value class for frequently used data types(e.g. `float[]`)
+///
+template <class dtype>
+struct TypeTrait;
+
+// TODO(syoyo): Support `Token` type
+template <>
+struct TypeTrait<std::string> {
+  static constexpr auto type_name = "string";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_STRING;
+};
+
+template <>
+struct TypeTrait<int> {
+  static constexpr auto type_name = "int";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_INT;
+};
+
+template <>
+struct TypeTrait<float16> {
+  static constexpr auto type_name = "half";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_HALF;
+};
+
+template <>
+struct TypeTrait<Vec2f> {
+  static constexpr auto type_name = "vec2f";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_VEC2F;
+};
+
+template <>
+struct TypeTrait<Vec3f> {
+  static constexpr auto type_name = "vec3f";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_VEC3F;
+};
+
+template <>
+struct TypeTrait<Vec4f> {
+  static constexpr auto type_name = "vec4f";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_VEC3F;
+};
+
+template <>
+struct TypeTrait<Matrix4d> {
+  static constexpr auto type_name = "matrix4d";
+  static constexpr ValueTypeId type_id = VALUE_TYPE_MATRIX4D;
+};
+
+template <class T>
+class PrimValue {
+ private:
+  T m_value;
+
+ public:
+  T value() const { return m_value; }
+
+  template <typename U, typename std::enable_if<std::is_same<T, U>::value>::type
+                            * = nullptr>
+  PrimValue<T> &operator=(const U &u) {
+    m_value = u;
+
+    return (*this);
+  }
+
+  std::string type_name() { return std::string(TypeTrait<T>::type_name); }
+  bool is_array() const { return false; }
+};
+
+///
+/// array of PrimmValue
+/// multi-dimensional type is not supported(e.g. float[][])
+///
+template <class T>
+class PrimValue<std::vector<T>> {
+ private:
+  std::vector<T> m_value;
+
+  template <typename U, typename std::enable_if<std::is_same<T, U>::value>::type
+                            * = nullptr>
+  PrimValue<T> &operator=(const std::vector<U> &u) {
+    m_value = u;
+
+    return (*this);
+  }
+
+  std::string type_name() {
+    return std::string(TypeTrait<T>::type_name) + "[]";
+  }
+
+  bool is_array() const { return true; }
+};
+
 ///
 /// Represent value.
 /// multi-dimensional type is not supported(e.g. float[][])
@@ -1519,8 +1640,7 @@ struct BlendShape {
                      // values in `offsets` and `normalOffsets`.
 };
 
-struct SkelRoot
-{
+struct SkelRoot {
   Extent extent;
   Purpose purpose{PurposeDefault};
   Visibility visibility{VisibilityInherited};
@@ -1531,15 +1651,16 @@ struct SkelRoot
 };
 
 // Skelton
-struct Skelton
-{
-  std::vector<Matrix4d> bindTransforms; // bind-pose transform of each joint in world coordinate.
+struct Skelton {
+  std::vector<Matrix4d>
+      bindTransforms;  // bind-pose transform of each joint in world coordinate.
   Extent extent;
 
   std::vector<std::string> jointNames;
   std::vector<std::string> joints;
 
-  std::vector<Matrix4d> restTransforms; // rest-pose transforms of each joint in local coordinate.
+  std::vector<Matrix4d> restTransforms;  // rest-pose transforms of each joint
+                                         // in local coordinate.
 
   Purpose purpose{PurposeDefault};
   Visibility visibility{VisibilityInherited};
@@ -1549,28 +1670,29 @@ struct Skelton
   // ref proxyPrim
 };
 
-struct SkelAnimation
-{
+struct SkelAnimation {
   std::vector<std::string> blendShapes;
   std::vector<float> blendShapeWeights;
   std::vector<std::string> joints;
-  std::vector<Quatf> rotations; // Joint-local unit quaternion rotations
-  std::vector<Vec3f> scales; // Joint-local scaling. pxr USD schema uses half3, but we use float3 for convenience.
-  std::vector<Vec3f> translations; // Joint-local translation.
-
+  std::vector<Quatf> rotations;  // Joint-local unit quaternion rotations
+  std::vector<Vec3f> scales;  // Joint-local scaling. pxr USD schema uses half3,
+                              // but we use float3 for convenience.
+  std::vector<Vec3f> translations;  // Joint-local translation.
 };
 
 // W.I.P.
 struct SkelBindingAPI {
-  Matrix4d geomBindTransform;  // primvars:skel:geomBindTransform
-  std::vector<int> jointIndices; // primvars:skel:jointIndices
-  std::vector<float> jointWeights; // primvars:skel:jointWeights
-  std::vector<std::string> blendShapes; // optional?
-  std::vector<std::string> joints; // optional
+  Matrix4d geomBindTransform;            // primvars:skel:geomBindTransform
+  std::vector<int> jointIndices;         // primvars:skel:jointIndices
+  std::vector<float> jointWeights;       // primvars:skel:jointWeights
+  std::vector<std::string> blendShapes;  // optional?
+  std::vector<std::string> joints;       // optional
 
-  int64_t animationSource{-1}; // index to Scene.animations. ref skel:animationSource
-  int64_t blendShapeTargets{-1}; // index to Scene.blendshapes. ref skel:bindShapeTargets
-  int64_t skeleton{-1}; // index to Scene.skeltons. // ref skel:skelton
+  int64_t animationSource{
+      -1};  // index to Scene.animations. ref skel:animationSource
+  int64_t blendShapeTargets{
+      -1};  // index to Scene.blendshapes. ref skel:bindShapeTargets
+  int64_t skeleton{-1};  // index to Scene.skeltons. // ref skel:skelton
 };
 
 // Polygon mesh geometry

src/usda-writer.cc

@@ -0,0 +1,39 @@
+#include "usda-writer.hh"
+
+#include <sstream>
+
+namespace tinyusdz {
+
+namespace {
+
+// TODO
+
+bool WriteNode(std::ostream &ofs, const Node &node, int indent) {
+  return false;
+}
+
+
+}
+
+bool SaveAsUSDA(const std::string &filename, const Scene &scene, std::string *warn, std::string *err) {
+  std::stringstream ss;
+
+  ss << "#usda 1.0\n";
+  ss << "(\n";
+  ss << "  doc = \"TinyUSDZ v" << tinyusdz::version_major << "." << tinyusdz::version_minor << "." << tinyusdz::version_micro << "\"\n";
+  ss << "  metersPerUnit = 1\n";
+  ss << "  upAxis = \"Z\"\n";
+  ss << ")\n";
+
+  // TODO
+
+  for (const auto &node : scene.nodes) {
+    if (!WriteNode(ss, node, 0)) {
+      return false;
+    }
+  }
+
+  return false;
+}
+
+} // namespace tinyusdz

src/usda-writer.hh

@@ -0,0 +1,12 @@
+#pragma once
+
+#include "tinyusdz.hh"
+
+namespace tinyusdz {
+
+///
+/// Save scene as USDA(ASCII)
+///
+bool SaveAsUSDA(const std::string &filename, const Scene &scene, std::string *warn, std::string *err);
+
+} // namespace tinyusdz