4 files changed, 56 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/fcurve.c b/source/blender/blenkernel/intern/fcurve.c
index 657a08877b0..dec410c8192 100644
--- a/source/blender/blenkernel/intern/fcurve.c
+++ b/source/blender/blenkernel/intern/fcurve.c
@@ -1730,10 +1730,20 @@ static float dvar_eval_transChan(ChannelDriver *driver, DriverVar *dvar)
      */
     float eul[3];
 
-    mat4_to_eulO(eul, rot_order, mat);
+    if (dtar->rotation_mode == DTAR_ROTMODE_AUTO) {
+      mat4_to_eulO(eul, rot_order, mat);
 
-    if (use_eulers) {
-      compatible_eul(eul, oldEul);
+      if (use_eulers) {
+        compatible_eul(eul, oldEul);
+      }
+    }
+    else if (dtar->rotation_mode >= DTAR_ROTMODE_EULER_MIN &&
+             dtar->rotation_mode <= DTAR_ROTMODE_EULER_MAX) {
+      mat4_to_eulO(eul, dtar->rotation_mode, mat);
+    }
+    else {
+      BLI_assert(false);
+      zero_v3(eul);
     }
 
     return eul[dtar->transChan - DTAR_TRANSCHAN_ROTX];
diff --git a/source/blender/editors/space_graph/graph_buttons.c b/source/blender/editors/space_graph/graph_buttons.c
index b264a5cb260..708d91a82bb 100644
--- a/source/blender/editors/space_graph/graph_buttons.c
+++ b/source/blender/editors/space_graph/graph_buttons.c
@@ -861,6 +861,11 @@ static void graph_panel_driverVar__transChan(uiLayout *layout, ID *id, DriverVar
 
   sub = uiLayoutColumn(layout, true);
   uiItemR(sub, &dtar_ptr, "transform_type", 0, NULL, ICON_NONE);
+
+  if (ELEM(dtar->transChan, DTAR_TRANSCHAN_ROTX, DTAR_TRANSCHAN_ROTY, DTAR_TRANSCHAN_ROTZ)) {
+    uiItemR(sub, &dtar_ptr, "rotation_mode", 0, IFACE_("Mode"), ICON_NONE);
+  }
+
   uiItemR(sub, &dtar_ptr, "transform_space", 0, IFACE_("Space"), ICON_NONE);
 }
 
diff --git a/source/blender/makesdna/DNA_anim_types.h b/source/blender/makesdna/DNA_anim_types.h
index 1718aabc51d..8c25d470a36 100644
--- a/source/blender/makesdna/DNA_anim_types.h
+++ b/source/blender/makesdna/DNA_anim_types.h
@@ -319,6 +319,10 @@ typedef struct DriverTarget {
   /** Transform channel index (for DVAR_TYPE_TRANSFORM_CHAN.)*/
   short transChan;
 
+  /** Rotation channel calculation type. */
+  char rotation_mode;
+  char _pad[7];
+
   /**
    * Flags for the validity of the target
    * (NOTE: these get reset every time the types change).
@@ -362,6 +366,23 @@ typedef enum eDriverTarget_TransformChannels {
   MAX_DTAR_TRANSCHAN_TYPES,
 } eDriverTarget_TransformChannels;
 
+/* Rotation channel mode for Driver Targets */
+typedef enum eDriverTarget_RotationMode {
+  /** Automatic euler mode. */
+  DTAR_ROTMODE_AUTO = 0,
+
+  /** Explicit euler rotation modes - must sync with BLI_math_rotation.h defines. */
+  DTAR_ROTMODE_EULER_XYZ = 1,
+  DTAR_ROTMODE_EULER_XZY,
+  DTAR_ROTMODE_EULER_YXZ,
+  DTAR_ROTMODE_EULER_YZX,
+  DTAR_ROTMODE_EULER_ZXY,
+  DTAR_ROTMODE_EULER_ZYX,
+
+  DTAR_ROTMODE_EULER_MIN = DTAR_ROTMODE_EULER_XYZ,
+  DTAR_ROTMODE_EULER_MAX = DTAR_ROTMODE_EULER_ZYX,
+} eDriverTarget_RotationMode;
+
 /* --- */
 
 /* maximum number of driver targets per variable */
diff --git a/source/blender/makesrna/intern/rna_fcurve.c b/source/blender/makesrna/intern/rna_fcurve.c
index 6c546940e6d..6cb3a18605c 100644
--- a/source/blender/makesrna/intern/rna_fcurve.c
+++ b/source/blender/makesrna/intern/rna_fcurve.c
@@ -1701,6 +1701,17 @@ static void rna_def_drivertarget(BlenderRNA *brna)
       {0, NULL, 0, NULL, NULL},
   };
 
+  static const EnumPropertyItem prop_rotation_mode_items[] = {
+      {DTAR_ROTMODE_AUTO, "AUTO", 0, "Auto Euler", "Euler using the rotation order of the target"},
+      {DTAR_ROTMODE_EULER_XYZ, "XYZ", 0, "XYZ Euler", "Euler using the XYZ rotation order"},
+      {DTAR_ROTMODE_EULER_XZY, "XZY", 0, "XZY Euler", "Euler using the XZY rotation order"},
+      {DTAR_ROTMODE_EULER_YXZ, "YXZ", 0, "YXZ Euler", "Euler using the YXZ rotation order"},
+      {DTAR_ROTMODE_EULER_YZX, "YZX", 0, "YZX Euler", "Euler using the YZX rotation order"},
+      {DTAR_ROTMODE_EULER_ZXY, "ZXY", 0, "ZXY Euler", "Euler using the ZXY rotation order"},
+      {DTAR_ROTMODE_EULER_ZYX, "ZYX", 0, "ZYX Euler", "Euler using the ZYX rotation order"},
+      {0, NULL, 0, NULL, NULL},
+  };
+
   srna = RNA_def_struct(brna, "DriverTarget", NULL);
   RNA_def_struct_ui_text(srna, "Driver Target", "Source of input values for driver variables");
 
@@ -1749,6 +1760,12 @@ static void rna_def_drivertarget(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Type", "Driver variable type");
   RNA_def_property_update(prop, 0, "rna_DriverTarget_update_data");
 
+  prop = RNA_def_property(srna, "rotation_mode", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_sdna(prop, NULL, "rotation_mode");
+  RNA_def_property_enum_items(prop, prop_rotation_mode_items);
+  RNA_def_property_ui_text(prop, "Rotation Mode", "Mode for calculating rotation channel values");
+  RNA_def_property_update(prop, 0, "rna_DriverTarget_update_data");
+
   prop = RNA_def_property(srna, "transform_space", PROP_ENUM, PROP_NONE);
   RNA_def_property_enum_bitflag_sdna(prop, NULL, "flag");
   RNA_def_property_enum_items(prop, prop_local_space_items);