simd: Generic-T Simd<T,W> abstraction

.github/workflows/weekly.yml

@@ -150,6 +150,8 @@ jobs:
           - { name: 'half',   image: '2026',           build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DUSE_BLOSC=OFF -DUSE_IMATH_HALF=ON' }
           - { name: 'sse',    image: '2026',           build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DOPENVDB_SIMD=SSE42' }
           - { name: 'avx',    image: '2026',           build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DOPENVDB_SIMD=AVX' }
+          - { name: 'simd',   image: '2026',           build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DOPENVDB_SIMD=AVX -DUSE_STD_SIMD=ON' }
+          - { name: 'simd-fallback', image: '2026',    build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DOPENVDB_SIMD=AVX -DUSE_STD_SIMD=OFF' }
           - { name: 'pygrid', image: '2026',           build: 'Release', components: 'core,python,bin,view,render,test', cmake: '-DOPENVDB_PYTHON_WRAP_ALL_GRID_TYPES=ON' }
           - { name: 'asan',   image: '2026',           build: 'asan',    components: 'core,test',                        cmake: '-DDISABLE_DEPENDENCY_VERSION_CHECKS=ON -DNANOVDB_USE_OPENVDB=ON -DOPENVDB_AX_STATIC=OFF -DOPENVDB_CORE_STATIC=OFF -DUSE_BLOSC=OFF' } # We never called blosc_destroy(), so disable blosc to silence these errors
           - { name: 'ubsan',  image: '2026',           build: 'ubsan',   components: 'core,test',                        cmake: '-DDISABLE_DEPENDENCY_VERSION_CHECKS=ON -DCMAKE_CXX_FLAGS="-Wno-deprecated-declarations" ' }

CMakeLists.txt

@@ -131,6 +131,13 @@ required.]=] ${USE_EXR})
 option(USE_PNG "Use PNG while building openvdb components." OFF)
 option(USE_AX "Use OpenVDB AX while building openvdb components." ${OPENVDB_BUILD_AX})
 option(USE_NANOVDB "Use NanoVDB while building openvdb components." ${OPENVDB_BUILD_NANOVDB})
+option(USE_STD_SIMD [=[
+Suppress auto-detection of std::experimental::simd (C++ Parallelism TS v2) and
+force the std::array fallback backend for openvdb::simd::Simd<T,W>.  By default
+the TS v2 header is used when the compiler provides it; set this to OFF to
+disable.  Has no effect on non-x86 or compilers that do not ship the TS header.
+Note: unlike USE_VCL this option requires no external dependency — the TS header
+is part of the compiler's standard library.]=] ON)
 
 cmake_dependent_option(OPENVDB_DISABLE_BOOST_IMPLICIT_LINKING
   "Disable the implicit linking of Boost libraries on Windows" ON "WIN32" OFF)
@@ -420,6 +427,11 @@ elseif(OPENVDB_SIMD STREQUAL "SSE42")
   add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:OPENVDB_USE_SSE42>")
 endif()
 
+# Suppress std::experimental::simd auto-detection if USE_STD_SIMD is OFF.
+if(NOT USE_STD_SIMD)
+  add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:OPENVDB_NO_STD_SIMD>")
+endif()
+
 #########################################################################
 
 # Configure our cmake modules to only search for static libraries

openvdb/openvdb/Platform.h

@@ -55,6 +55,17 @@
     #endif
 #endif
 
+/// Auto-detect std::experimental::simd (C++ Parallelism TS v2).
+/// When available, openvdb::simd::Simd<T,W> wraps it to emit native SIMD
+/// instructions without relying on the auto-vectorizer.
+/// Suppress with -DOPENVDB_NO_STD_SIMD to force the std::array fallback.
+#if !defined(OPENVDB_NO_STD_SIMD) && defined(__has_include) && __has_include(<experimental/simd>)
+#  include <experimental/simd>
+#  ifdef __cpp_lib_experimental_parallel_simd
+#    define OPENVDB_USE_STD_SIMD 1
+#  endif
+#endif
+
 /// Windows defines
 #ifdef _WIN32
     ///Disable the non-portable Windows definitions of min() and max() macros

openvdb/openvdb/points/impl/PointRasterizeEllipsoidsSDFImpl.h

@@ -399,6 +399,20 @@ struct EllipsoidTransferQuat final :
         this->BaseT::rasterizePoint(ijk, id, bounds, R);
     }
 
+    /// @brief  Point-by-point dispatch — ellipsoids are not batchable via
+    ///   the spherical SIMD path.  This override prevents SphericalTransfer::
+    ///   rasterizePoints (which calls rasterizeN2) from being instantiated for
+    ///   the FixedBandRadius<Vec3f> radius type used by ellipsoids.
+    inline void rasterizePoints(const Coord& ijk,
+                    const Index start,
+                    const Index end,
+                    const CoordBBox& bounds)
+    {
+        for (Index i = start; i < end; ++i) {
+            this->rasterizePoint(ijk, i, bounds);
+        }
+    }
+
 private:
     std::unique_ptr<QuatHandleT> mRotationHandle;
 };
@@ -446,6 +460,17 @@ struct EllipsoidTransferMat3 final :
         this->BaseT::rasterizePoint(ijk, id, bounds, mXformHandle->get(id));
     }
 
+    /// @brief  See EllipsoidTransferQuat::rasterizePoints.
+    inline void rasterizePoints(const Coord& ijk,
+                    const Index start,
+                    const Index end,
+                    const CoordBBox& bounds)
+    {
+        for (Index i = start; i < end; ++i) {
+            this->rasterizePoint(ijk, i, bounds);
+        }
+    }
+
 private:
     std::unique_ptr<XformHandleT> mXformHandle;
 };