diff --git a/pxr/imaging/plugin/hdEmbree/pxrIES/README.md b/pxr/imaging/plugin/hdEmbree/pxrIES/README.md
new file mode 100644
index 0000000000..ae97b47b0c
--- /dev/null
+++ b/pxr/imaging/plugin/hdEmbree/pxrIES/README.md
@@ -0,0 +1,31 @@
+# IES utilities
+
+Utilities for reading and using .ies files (IESNA LM-63 Format), which are used
+to describe lights.
+
+The files `ies.h` and `ies.cpp` are originally from
+[Cycles](https://docs.blender.org/manual/en/latest/render/cycles/index.html),
+which is part of the larger
+[Blender](https://projects.blender.org/blender/blender/) project, though with
+a the less restrictive Apache 2.0 license - see:
+
+- https://www.blender.org/about/license/
+
+## Version
+
+v4.1.1 ( 53c49589f311bd3c9e3ea8f62b3fa8fe8e5d2c8c )
+
+## Setup
+
+When updating IES, the following steps should be followed:
+
+1. Copy `intern/cycles/util/ies.h` and `intern/cycles/util/ies.cpp` over the
+   copies in `pxr/imaging/plugin/hdEmbree/pxrIES`.
+2. Apply `pxr-IES.patch` to update the source files with modifications for USD,
+   ie, from the USD repo root folder:
+
+   ```sh
+   patch -p1 -i pxr/imaging/plugin/hdEmbree/pxrIES/pxr-IES.patch
+   ```
+3. Commit your changes, noting the exact version of blender that the new ies
+   files were copied from.
\ No newline at end of file
diff --git a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp
index a6725cc049..7a6917303c 100644
--- a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp
+++ b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp
@@ -2,21 +2,22 @@
  *
  * SPDX-License-Identifier: Apache-2.0 */
 
+#include "ies.h"
 #include <algorithm>
+#include <cstring>
 
-#include "util/foreach.h"
-#include "util/ies.h"
-#include "util/math.h"
-#include "util/string.h"
+#define _USE_MATH_DEFINES
+#include <cmath>
 
-CCL_NAMESPACE_BEGIN
+#if !defined(M_PI)
+#define M_PI 3.14159265358979323846
+#endif
 
-// NOTE: For some reason gcc-7.2 does not instantiate this version of the
-// allocator here (used in IESTextParser). Works fine for gcc-6, gcc-7.3 and gcc-8.
-//
-// TODO(sergey): Get to the root of this issue, or confirm this is a compiler
-// issue.
-template class GuardedAllocator<char>;
+#define M_PI_F M_PI
+
+PXR_NAMESPACE_OPEN_SCOPE
+
+namespace pxr_ccl {
 
 bool IESFile::load(const string &ies)
 {
@@ -43,11 +44,28 @@ int IESFile::packed_size()
   return 0;
 }
 
+template <class To, class From>
+std::enable_if_t<sizeof(To) == sizeof(From) &&
+                     std::is_trivially_copyable_v<From> &&
+                     std::is_trivially_copyable_v<To>,
+                 To>
+// constexpr support needs compiler magic
+bit_cast(const From &src) noexcept
+{
+  static_assert(std::is_trivially_constructible_v<To>,
+                "This implementation additionally requires "
+                "destination type to be trivially constructible");
+
+  To dst;
+  std::memcpy(&dst, &src, sizeof(To));
+  return dst;
+}
+
 void IESFile::pack(float *data)
 {
   if (v_angles.size() && h_angles.size()) {
-    *(data++) = __int_as_float(h_angles.size());
-    *(data++) = __int_as_float(v_angles.size());
+    *(data++) = bit_cast<float>(static_cast<int>(h_angles.size()));
+    *(data++) = bit_cast<float>(static_cast<int>(v_angles.size()));
 
     memcpy(data, &h_angles[0], h_angles.size() * sizeof(float));
     data += h_angles.size();
@@ -407,4 +425,7 @@ IESFile::~IESFile()
   clear();
 }
 
-CCL_NAMESPACE_END
+} // namespace pxr_ccl
+
+PXR_NAMESPACE_CLOSE_SCOPE
+
diff --git a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h
index 8c506befdd..051c23f6c4 100644
--- a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h
+++ b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h
@@ -5,10 +5,18 @@
 #ifndef __UTIL_IES_H__
 #define __UTIL_IES_H__
 
-#include "util/string.h"
-#include "util/vector.h"
+#include <string>
+#include <vector>
+
+using std::string;
+using std::vector;
+
+#include "pxr/pxr.h"
+
+PXR_NAMESPACE_OPEN_SCOPE
+
+namespace pxr_ccl {
 
-CCL_NAMESPACE_BEGIN
 
 class IESFile {
  public:
@@ -19,11 +27,16 @@ class IESFile {
   void pack(float *data);
 
   bool load(const string &ies);
+
+  virtual
   void clear();
 
  protected:
   bool parse(const string &ies);
+
+  virtual
   bool process();
+
   void process_type_a();
   void process_type_b();
   void process_type_c();
@@ -41,6 +54,8 @@ class IESFile {
   enum IESType { TYPE_A = 3, TYPE_B = 2, TYPE_C = 1 } type;
 };
 
-CCL_NAMESPACE_END
+} // namespace pxr_ccl
+
+PXR_NAMESPACE_CLOSE_SCOPE
 
 #endif /* __UTIL_IES_H__ */
diff --git a/pxr/imaging/plugin/hdEmbree/pxrIES/pxr-IES.patch b/pxr/imaging/plugin/hdEmbree/pxrIES/pxr-IES.patch
new file mode 100644
index 0000000000..acef74a69b
--- /dev/null
+++ b/pxr/imaging/plugin/hdEmbree/pxrIES/pxr-IES.patch
@@ -0,0 +1,131 @@
+diff --git a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp
+index a6725cc04..7a6917303 100644
+--- a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp
++++ b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.cpp
+@@ -2,21 +2,22 @@
+  *
+  * SPDX-License-Identifier: Apache-2.0 */
+ 
++#include "ies.h"
+ #include <algorithm>
++#include <cstring>
+ 
+-#include "util/foreach.h"
+-#include "util/ies.h"
+-#include "util/math.h"
+-#include "util/string.h"
++#define _USE_MATH_DEFINES
++#include <cmath>
+ 
+-CCL_NAMESPACE_BEGIN
++#if !defined(M_PI)
++#define M_PI 3.14159265358979323846
++#endif
+ 
+-// NOTE: For some reason gcc-7.2 does not instantiate this version of the
+-// allocator here (used in IESTextParser). Works fine for gcc-6, gcc-7.3 and gcc-8.
+-//
+-// TODO(sergey): Get to the root of this issue, or confirm this is a compiler
+-// issue.
+-template class GuardedAllocator<char>;
++#define M_PI_F M_PI
++
++PXR_NAMESPACE_OPEN_SCOPE
++
++namespace pxr_ccl {
+ 
+ bool IESFile::load(const string &ies)
+ {
+@@ -43,11 +44,28 @@ int IESFile::packed_size()
+   return 0;
+ }
+ 
++template <class To, class From>
++std::enable_if_t<sizeof(To) == sizeof(From) &&
++                     std::is_trivially_copyable_v<From> &&
++                     std::is_trivially_copyable_v<To>,
++                 To>
++// constexpr support needs compiler magic
++bit_cast(const From &src) noexcept
++{
++  static_assert(std::is_trivially_constructible_v<To>,
++                "This implementation additionally requires "
++                "destination type to be trivially constructible");
++
++  To dst;
++  std::memcpy(&dst, &src, sizeof(To));
++  return dst;
++}
++
+ void IESFile::pack(float *data)
+ {
+   if (v_angles.size() && h_angles.size()) {
+-    *(data++) = __int_as_float(h_angles.size());
+-    *(data++) = __int_as_float(v_angles.size());
++    *(data++) = bit_cast<float>(static_cast<int>(h_angles.size()));
++    *(data++) = bit_cast<float>(static_cast<int>(v_angles.size()));
+ 
+     memcpy(data, &h_angles[0], h_angles.size() * sizeof(float));
+     data += h_angles.size();
+@@ -407,4 +425,7 @@ IESFile::~IESFile()
+   clear();
+ }
+ 
+-CCL_NAMESPACE_END
++} // namespace pxr_ccl
++
++PXR_NAMESPACE_CLOSE_SCOPE
++
+diff --git a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h
+index 8c506befd..051c23f6c 100644
+--- a/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h
++++ b/pxr/imaging/plugin/hdEmbree/pxrIES/ies.h
+@@ -5,10 +5,18 @@
+ #ifndef __UTIL_IES_H__
+ #define __UTIL_IES_H__
+ 
+-#include "util/string.h"
+-#include "util/vector.h"
++#include <string>
++#include <vector>
++
++using std::string;
++using std::vector;
++
++#include "pxr/pxr.h"
++
++PXR_NAMESPACE_OPEN_SCOPE
++
++namespace pxr_ccl {
+ 
+-CCL_NAMESPACE_BEGIN
+ 
+ class IESFile {
+  public:
+@@ -19,11 +27,16 @@ class IESFile {
+   void pack(float *data);
+ 
+   bool load(const string &ies);
++
++  virtual
+   void clear();
+ 
+  protected:
+   bool parse(const string &ies);
++
++  virtual
+   bool process();
++
+   void process_type_a();
+   void process_type_b();
+   void process_type_c();
+@@ -41,6 +54,8 @@ class IESFile {
+   enum IESType { TYPE_A = 3, TYPE_B = 2, TYPE_C = 1 } type;
+ };
+ 
+-CCL_NAMESPACE_END
++} // namespace pxr_ccl
++
++PXR_NAMESPACE_CLOSE_SCOPE
+ 
+ #endif /* __UTIL_IES_H__ */