Add some Tydra utility functions.

CMakeLists.txt

@@ -306,6 +306,7 @@ set(TINYUSDZ_SOURCES
     ${PROJECT_SOURCE_DIR}/src/image-loader.cc
     ${PROJECT_SOURCE_DIR}/src/pprinter.cc
     ${PROJECT_SOURCE_DIR}/src/stage.cc
+    ${PROJECT_SOURCE_DIR}/src/tydra/prim-apply.cc
     ${PROJECT_SOURCE_DIR}/src/tydra/scene-access.cc
     ${PROJECT_SOURCE_DIR}/src/tydra/shader-network.cc
     ${PROJECT_SOURCE_DIR}/src/tydra/render-data.cc)

MANIFEST.in

@@ -533,6 +533,8 @@ include src/tinyusdz.hh
 include src/tiny-variant.hh
 include src/token-type.hh
 include src/tydra/README.md
+include src/tydra/prim-apply.cc
+include src/tydra/prim-apply.hh
 include src/tydra/render-data.cc
 include src/tydra/render-data.hh
 include src/tydra/scene-access.cc

examples/sdlviewer/CMakeLists.txt

@@ -294,8 +294,9 @@ list(
   ../../src/ascii-parser-timesamples-array.cc
   ../../src/usdc-reader.cc
   ../../src/usda-reader.cc
-  #../../src/usda-writer.cc
+  ../../src/usda-writer.cc
   ../../src/image-loader.cc
+  ../../src/linear-algebra.cc
   ../../src/value-types.cc
   ../../src/value-pprint.cc
   ../../src/tiny-format.cc
@@ -308,6 +309,8 @@ list(
   ../../src/linear-algebra.cc
   ../../src/tydra/render-data.cc
   ../../src/tydra/scene-access.cc
+  ../../src/tydra/shader-network.cc
+  ../../src/tydra/prim-apply.cc
 )
 
 set(TINYUSDZ_DEP_SOURCES

src/tydra/prim-apply.cc

@@ -0,0 +1,46 @@
+#include "prim-apply.hh"
+
+#include "prim-types.hh"
+#include "usdGeom.hh"
+
+namespace tinyusdz {
+namespace tydra {
+
+bool ApplyToGPrim(
+  const Stage &stage, const Prim &prim,
+  std::function<bool(const Stage &stage, const GPrim *gprim)> fn) {
+
+  (void)stage;
+
+  if ((value::TypeId::TYPE_ID_GPRIM <= prim.type_id() && 
+      (value::TypeId::TYPE_ID_GEOM_END > prim.type_id()))) {
+    // gprim 
+  } else {
+    return false;
+  }
+
+#define APPLY_FUN(__ty) { \
+  const auto *v = prim.as<__ty>(); \
+  if (v) { \
+    return fn(stage, v); \
+  } \
+  }
+  
+  APPLY_FUN(GPrim)
+  APPLY_FUN(Xform)
+  APPLY_FUN(GeomMesh)
+  APPLY_FUN(GeomSphere)
+  APPLY_FUN(GeomCapsule)
+  APPLY_FUN(GeomCube)
+  APPLY_FUN(GeomPoints)
+  APPLY_FUN(GeomCylinder)
+  APPLY_FUN(GeomBasisCurves)
+  
+#undef APPLY_FUN
+
+  return false;
+
+}
+
+} // namespace tydra
+} // namespace tinyusdz

src/tydra/prim-apply.hh

@@ -0,0 +1,22 @@
+#pragma once
+
+// utility to apply function to a Prim.
+// Internal use expected(not intended for Public Tydra API).
+
+#include <functional>
+
+namespace tinyusdz {
+
+// forward decl.
+class Stage;
+class Prim;
+struct GPrim;
+
+namespace tydra {
+
+bool ApplyToGPrim(
+  const Stage &stage, const Prim &prim,
+  std::function<bool(const Stage &stage, const GPrim *gprim)> fn);
+
+} // namespace tydra
+} // namespace tinyusdz

src/tydra/shader-network.cc

@@ -1,9 +1,12 @@
 #include "shader-network.hh"
+#include "prim-apply.hh"
 
+#include "prim-types.hh"
 #include "usdShade.hh"
 #include "pprinter.hh"
 #include "prim-pprint.hh"
 #include "value-pprint.hh"
+#include "stage.hh"
 
 namespace tinyusdz {
 namespace tydra {
@@ -129,5 +132,102 @@ INSTANCIATE_EVAL_SHADER(value::matrix4d);
 
 // instanciations
 
+namespace {
+
+bool GetSinglePath(const Relationship &rel, Path *path) {
+  if (!path) {
+    return false;
+  }
+
+  if (rel.is_path()) {
+    (*path) = rel.targetPath;
+    return true;
+  } else if (rel.is_pathvector()) {
+    if (rel.targetPathVector.size() > 0) {
+      (*path) = rel.targetPathVector[0];
+      return true;
+    }
+  }
+
+  return false;
+}
+
+} // namespace local
+
+bool GetBoundMaterial(
+  const Stage &_stage,
+  const Prim &prim,
+  const std::string &suffix,
+  tinyusdz::Path *materialPath, 
+  const Material **material,
+  std::string *err) {
+
+  if (materialPath == nullptr) {
+    return false;
+  }
+
+  (void)err;
+  
+  auto apply_fun = [&](const Stage &stage, const GPrim *gprim) -> bool {
+    if (suffix.empty()) {
+      if (gprim->materialBinding.has_value()) {
+        if (GetSinglePath(gprim->materialBinding.value(), materialPath)) {
+
+          const Prim *p;
+          if (stage.find_prim_at_path(*materialPath, p, err)) {
+            if (p->is<Material>() && (material != nullptr)) {
+              (*material) = p->as<Material>();
+            } else {
+              (*material) = nullptr;
+            }
+          }
+          
+          return true;
+        }
+      }
+    } else if (suffix == "correction") {
+      if (gprim->materialBindingCorrection.has_value()) {
+        if (GetSinglePath(gprim->materialBindingCorrection.value(), materialPath)) {
+
+          const Prim *p;
+          if (stage.find_prim_at_path(*materialPath, p, err)) {
+            if (p->is<Material>() && (material != nullptr)) {
+              (*material) = p->as<Material>();
+            } else {
+              (*material) = nullptr;
+            }
+          }
+          
+          return true;
+        }
+      }
+    } else if (suffix == "preview") {
+      if (gprim->materialBindingPreview.has_value()) {
+        if (GetSinglePath(gprim->materialBindingPreview.value(), materialPath)) {
+
+          const Prim *p;
+          if (stage.find_prim_at_path(*materialPath, p, err)) {
+            if (p->is<Material>() && (material != nullptr)) {
+              (*material) = p->as<Material>();
+            } else {
+              (*material) = nullptr;
+            }
+          }
+          
+          return true;
+        }
+      }
+    } else {
+      return false;
+    } 
+
+    return false;
+  };
+
+  bool ret = ApplyToGPrim(_stage, prim, apply_fun);
+
+  return ret;
+}
+
 } // namespace tydra
 } // namespace tinyusdz

src/tydra/shader-network.hh

@@ -10,9 +10,12 @@
 
 namespace tinyusdz {
 
-// forward decl of usdShade
+// forward decl of prim-types.hh
+class Path;
 class Stage;
 class Prim;
+
+// forward decl of usdShade
 struct Material;
 struct Shader;
 
@@ -62,5 +65,28 @@ bool EvaluateShaderAttribute(
 // Currently float2 only
 //std::vector<UsdPrimvarReader_float2> ExtractPrimvarReadersFromMaterialNode(const Prim &node);
 
+
+///
+/// Get material:binding target Path.
+/// The bahavior is:
+///
+/// 1. If material:binding is assigned to given Prim, return it
+/// 2. Look into parent Prim's material:binding
+///
+/// @param[in] stage Prim
+/// @param[in] prim Prim
+/// @param[in] suffix extra suffix(e.g. empty string is given, look into `material:binding`. `correction` is given, look into `material:binding:correction`.)
+/// @param[out] materialPath Found target Path.
+/// @param[out] material THe pointer to found Material object in Stage(if no Material object found in Stage, returns nullptr)
+/// @return true when bound Material Path is found.
+///
+bool GetBoundMaterial(
+  const Stage &stage,
+  const Prim &prim,
+  const std::string &suffix,
+  tinyusdz::Path *materialPath, 
+  const Material **material,
+  std::string *err);
+
 }  // namespace tydra
 }  // namespace tinyusdz

src/usdGeom.hh

@@ -25,6 +25,10 @@ constexpr auto kGeomSphere = "Sphere";
 constexpr auto kGeomCamera = "Camera";
 constexpr auto kPointInstancer = "PointInstancer";
 
+constexpr auto kMaterialBinding = "material:binding";
+constexpr auto kMaterialBindingCorrection = "material:binding:correction";
+constexpr auto kMaterialBindingPreview = "material:binding:preview";
+
 struct GPrim;
 
 bool IsSupportedGeomPrimvarType(uint32_t tyid);