https://src.fedoraproject.org/rpms/Field3D/raw/rawhide/f/Field3D-openexr.patch
https://github.com/imageworks/Field3D/issues/101

--- a/export/StdMathLib.h
+++ b/export/StdMathLib.h
@@ -38,18 +38,41 @@
 #ifndef _INCLUDED_Field3D_StdMathLib_H_
 #define _INCLUDED_Field3D_StdMathLib_H_
 
-#include <OpenEXR/ImathBox.h> 
-#include <OpenEXR/ImathBoxAlgo.h>
-#include <OpenEXR/ImathColor.h>
-#include <OpenEXR/ImathHalfLimits.h>
-#include <OpenEXR/ImathMatrix.h>
-#include <OpenEXR/ImathMatrixAlgo.h>
-#include <OpenEXR/ImathPlane.h>
-#include <OpenEXR/ImathRandom.h> 
-#include <OpenEXR/ImathRoots.h>
-#include <OpenEXR/ImathVec.h>
-#include <OpenEXR/half.h> 
+// The version can reliably be found in this header file from OpenEXR,
+// for both 2.x and 3.x:
+#include <OpenEXR/OpenEXRConfig.h>
+#define COMBINED_OPENEXR_VERSION ((10000*OPENEXR_VERSION_MAJOR) + \
+                                  (100*OPENEXR_VERSION_MINOR) + \
+                                  OPENEXR_VERSION_PATCH)
 
+// There's just no easy way to have an `#include` that works in both
+// cases, so we use the version to switch which set of include files we
+// use.
+#if COMBINED_OPENEXR_VERSION >= 20599 /* 2.5.99: pre-3.0 */
+#   include <Imath/ImathBox.h>
+#   include <Imath/ImathBoxAlgo.h>
+#   include <Imath/ImathColor.h>
+#   include <Imath/ImathMatrix.h>
+#   include <Imath/ImathMatrixAlgo.h>
+#   include <Imath/ImathPlane.h>
+#   include <Imath/ImathRandom.h>
+#   include <Imath/ImathRoots.h>
+#   include <Imath/ImathVec.h>
+#   include <Imath/half.h>
+#else
+    // OpenEXR 2.x, use the old locations
+#   include <OpenEXR/ImathBox.h>
+#   include <OpenEXR/ImathBoxAlgo.h>
+#   include <OpenEXR/ImathColor.h>
+#   include <OpenEXR/ImathHalfLimits.h>
+#   include <OpenEXR/ImathMatrix.h>
+#   include <OpenEXR/ImathMatrixAlgo.h>
+#   include <OpenEXR/ImathPlane.h>
+#   include <OpenEXR/ImathRandom.h>
+#   include <OpenEXR/ImathRoots.h>
+#   include <OpenEXR/ImathVec.h>
+#   include <OpenEXR/half.h>
+#endif
 //----------------------------------------------------------------------------//
 
 #include "ns.h"
--- a/export/Curve.h
+++ b/export/Curve.h
@@ -53,8 +53,25 @@
 
 #include <boost/lexical_cast.hpp>
 
-#include <OpenEXR/ImathFun.h>
-#include <OpenEXR/ImathMatrix.h>
+// The version can reliably be found in this header file from OpenEXR,
+// for both 2.x and 3.x:
+#include <OpenEXR/OpenEXRConfig.h>
+#define COMBINED_OPENEXR_VERSION ((10000*OPENEXR_VERSION_MAJOR) + \
+                                  (100*OPENEXR_VERSION_MINOR) + \
+                                  OPENEXR_VERSION_PATCH)
+
+// There's just no easy way to have an `#include` that works in both
+// cases, so we use the version to switch which set of include files we
+// use.
+#if COMBINED_OPENEXR_VERSION >= 20599 /* 2.5.99: pre-3.0 */
+#   include <Imath/ImathFun.h>
+#   include <Imath/ImathMatrix.h>
+#else
+    // OpenEXR 2.x, use the old locations
+#   include <OpenEXR/ImathFun.h>
+#   include <OpenEXR/ImathMatrix.h>
+#endif
+
 
 //----------------------------------------------------------------------------//
 
--- a/include/OgUtil.h
+++ b/include/OgUtil.h
@@ -10,7 +10,22 @@
 #include <iostream>
 #include <string>
 
-#include <OpenEXR/ImathVec.h>
+// The version can reliably be found in this header file from OpenEXR,
+// for both 2.x and 3.x:
+#include <OpenEXR/OpenEXRConfig.h>
+#define COMBINED_OPENEXR_VERSION ((10000*OPENEXR_VERSION_MAJOR) + \
+                                  (100*OPENEXR_VERSION_MINOR) + \
+                                  OPENEXR_VERSION_PATCH)
+
+// There's just no easy way to have an `#include` that works in both
+// cases, so we use the version to switch which set of include files we
+// use.
+#if COMBINED_OPENEXR_VERSION >= 20599 /* 2.5.99: pre-3.0 */
+#   include <Imath/ImathVec.h>
+#else
+    // OpenEXR 2.x, use the old locations
+#   include <OpenEXR/ImathVec.h>
+#endif
 
 #include "All.h"
 #include "UtilFoundation.h"
--- a/include/UtilFoundation.h
+++ b/include/UtilFoundation.h
@@ -68,7 +68,22 @@
 
 #include <memory>
 
-#include <half.h>
+// The version can reliably be found in this header file from OpenEXR,
+// for both 2.x and 3.x:
+#include <OpenEXR/OpenEXRConfig.h>
+#define COMBINED_OPENEXR_VERSION ((10000*OPENEXR_VERSION_MAJOR) + \
+                                  (100*OPENEXR_VERSION_MINOR) + \
+                                  OPENEXR_VERSION_PATCH)
+
+// There's just no easy way to have an `#include` that works in both
+// cases, so we use the version to switch which set of include files we
+// use.
+#if COMBINED_OPENEXR_VERSION >= 20599 /* 2.5.99: pre-3.0 */
+#   include <Imath/half.h>
+#else
+    // OpenEXR 2.x, use the old locations
+#   include <OpenEXR/half.h>
+#endif
 
 #include <iomanip>
 #include <iostream>
--- a/include/OgIAttribute.h
+++ b/include/OgIAttribute.h
@@ -9,7 +9,22 @@
 
 #include "OgUtil.h"
 
-#include <OpenEXR/ImathMatrix.h>
+// The version can reliably be found in this header file from OpenEXR,
+// for both 2.x and 3.x:
+#include <OpenEXR/OpenEXRConfig.h>
+#define COMBINED_OPENEXR_VERSION ((10000*OPENEXR_VERSION_MAJOR) + \
+                                  (100*OPENEXR_VERSION_MINOR) + \
+                                  OPENEXR_VERSION_PATCH)
+
+// There's just no easy way to have an `#include` that works in both
+// cases, so we use the version to switch which set of include files we
+// use.
+#if COMBINED_OPENEXR_VERSION >= 20599 /* 2.5.99: pre-3.0 */
+#   include <Imath/ImathMatrix.h>
+#else
+    // OpenEXR 2.x, use the old locations
+#   include <OpenEXR/ImathMatrix.h>
+#endif
 
 //----------------------------------------------------------------------------//
 
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,7 +49,13 @@ FIND_PACKAGE (Boost COMPONENTS regex thr
 FIND_PACKAGE (MPI)
 ENDIF ()
 
-FIND_PACKAGE (ILMBase)
+# First, try to find just the right config files
+find_package(Imath CONFIG)
+if (NOT TARGET Imath::Imath)
+    # Couldn't find Imath::Imath, maybe it's older and has IlmBase?
+    find_package(IlmBase CONFIG)
+endif ()
+find_package(OpenEXR CONFIG)
 
 # Allow the developer to select if Dynamic or Static libraries are built
 OPTION (BUILD_SHARED_LIBS "Build Shared Libraries" ON)
@@ -146,9 +152,20 @@ IF ( CMAKE_HOST_UNIX )
       LIST ( APPEND Field3D_Libraries_Shared
              ${MPI_LIBRARIES} )
   ENDIF ( MPI_FOUND )
-  LIST ( APPEND Field3D_Libraries_Shared
-    Iex Half IlmThread Imath
-    pthread dl z )
+  if(TARGET Imath::Imath)
+	  list(APPEND Field3D_Libraries_Shared
+        # For OpenEXR/Imath 3.x:
+          $<$<TARGET_EXISTS:OpenEXR::OpenEXR>:OpenEXR::OpenEXR>
+          $<$<TARGET_EXISTS:Imath::Imath>:Imath::Imath>
+          $<$<TARGET_EXISTS:Imath::Half>:Imath::Half>
+		  pthread
+		  dl
+		  z)
+  else()
+    LIST ( APPEND Field3D_Libraries_Shared
+        Iex Half IlmThread Imath
+        pthread dl z )
+  endif()
   SET ( Field3D_DSO_Libraries ${Field3D_Libraries_Shared} )
   SET ( Field3D_BIN_Libraries Field3D ${Field3D_Libraries_Shared}
         ${Boost_LIBRARIES} )
--- a/test/unit_tests/UnitTest.cpp
+++ b/test/unit_tests/UnitTest.cpp
@@ -44,7 +44,22 @@
 #include <boost/thread/thread.hpp>
 #include <boost/thread/mutex.hpp>
 
-#include <OpenEXR/ImathFrustum.h>
+// The version can reliably be found in this header file from OpenEXR,
+// for both 2.x and 3.x:
+#include <OpenEXR/OpenEXRConfig.h>
+#define COMBINED_OPENEXR_VERSION ((10000*OPENEXR_VERSION_MAJOR) + \
+                                  (100*OPENEXR_VERSION_MINOR) + \
+                                  OPENEXR_VERSION_PATCH)
+
+// There's just no easy way to have an `#include` that works in both
+// cases, so we use the version to switch which set of include files we
+// use.
+#if COMBINED_OPENEXR_VERSION >= 20599 /* 2.5.99: pre-3.0 */
+#   include <Imath/ImathFrustum.h>
+#else
+    // OpenEXR 2.x, use the old locations
+#   include <OpenEXR/ImathFrustum.h>
+#endif
 
 #include "Field3D/DenseField.h"
 #include "Field3D/EmptyField.h"