diff --git a/LuaLibs/AddManData.lua b/LuaLibs/AddManData.lua
index 2aefe40..63d780b 100644
--- a/LuaLibs/AddManData.lua
+++ b/LuaLibs/AddManData.lua
@@ -315,6 +315,8 @@ LAY_AUX_SOLIDS = 'AuxSolids'
 LAY_SHELL_NBR = 'ShellNumber'
 LAY_AUX = 'Aux'
 SPINE_CURVE = 'Spine'
+SPINE_PLANE = 'Plane'
+SPINE_FROM_PLANES = 'SpineComputedFromPlanes'
 LAY_FRAME = 'Frame'
 VIEWPARAMS = 'ViewParams'
 IMPORTED_SOLID = 'ImportedSolid'
diff --git a/LuaLibs/CalcSlices.lua b/LuaLibs/CalcSlices.lua
index fed4fe3..15e5a5f 100644
--- a/LuaLibs/CalcSlices.lua
+++ b/LuaLibs/CalcSlices.lua
@@ -56,13 +56,13 @@ local function ComputeSlicingData( vIds, vtSlicing, dSliceStep, dMaxH, nMaxSlice
 end
 
 ---------------------------------------------------------------------
-local function ComputeMultiplanarSlicingData( dSliceStep, nMaxSlicesNbr, nSlicingType)
-   -- le direzioni e i valori di slicing sono le normali e i punti che definiscono i piani di slicing e vengono calcolati sulla curva "Spine"
-   
-   -- recupero la curva guida ( è la prima nel gruppo aux con info NameEntity = Spine oppure quella con nome Spine)
+local function GetMultiplanarGuide( nStmId, nSlicingType)
+
    local nAuxLayId = EgtGetFirstNameInGroup( s_nPartId, LAY_AUX)
    local vIds = EgtGetAllInGroup( nAuxLayId)
    local nSpineId
+   
+   -- verfico se definita curva guida ( è la prima nel gruppo aux con info NameEntity = Spine oppure quella con nome Spine)
    for i = 1, #vIds do
       local sNameEntity = EgtGetInfo( vIds[i], KEY_ENTITY_NAME)
       if sNameEntity == SPINE_CURVE then
@@ -72,6 +72,99 @@ local function ComputeMultiplanarSlicingData( dSliceStep, nMaxSlicesNbr, nSlicin
          nSpineId = vIds[i]
       end
    end
+   
+   if nSpineId then
+      return nSpineId
+   end
+   
+   -- se curva non definita deve essere calcolata a partire dai piani
+   local vPoints = {}
+   local vNormals = {}
+   local nGrpTmp = EgtGroup( nAuxLayId)
+   for i = 1, #vIds do
+      -- cerco il piano i-esimo tramite nome o info EntityName
+      local nPlaneId = EgtGetFirstNameInGroup( nAuxLayId, SPINE_PLANE .. tostring( i))
+      if not nPlaneId then
+         for j = 1, #vIds do
+            if EgtGetInfo( vIds[j], KEY_ENTITY_NAME) == SPINE_PLANE .. tostring( i) then
+               nPlaneId = vIds[j]
+               break
+            end
+         end
+      end
+      if not nPlaneId or EgtGetType( nPlaneId) ~= GDB_TY.SRF_MESH then
+         break
+      end
+      
+      local ptOn, vtN = EgtSurfTmFacetCenter( nPlaneId, 0, GDB_ID.ROOT)
+      -- come origine del piano considero il centroide dell'intersezione fra il solido e il piano
+      if nStmId then
+         local dDelta = 0
+         local nRes, nPntCnt, nCrvCnt, nSrfCnt = EgtPlaneSurfTmInters( ptOn, vtN, nStmId, nGrpTmp, GDB_RT.GLOB)
+         -- se fallisce ritento spostando leggermente il piano
+         if not nRes then
+            dDelta = EgtIf( i == 1, DELTAZ, - DELTAZ)
+            nRes, nPntCnt, nCrvCnt, nSrfCnt = EgtPlaneSurfTmInters( ptOn + dDelta * vtN, vtN, nStmId, nGrpTmp, GDB_RT.GLOB)
+         end
+         if nSrfCnt > 0 then
+            ptOn = EgtGP( nRes + nPntCnt + nCrvCnt, GDB_ID.ROOT) - dDelta * vtN
+         else
+            for nCrvId = nRes + nPntCnt, nRes + nPntCnt + nCrvCnt - 1 do
+               if EgtCurveIsClosed( nCrvId) then
+                  ptOn = EgtGP( nCrvId, GDB_ID.ROOT) - dDelta * vtN
+                  break
+               end
+            end
+         end
+      end
+      table.insert( vPoints, ptOn)
+      table.insert( vNormals, vtN)
+   end
+   
+   -- costruisco la guida a partire dai punti e dalle tangenti
+   if #vPoints > 0 then
+      
+      if nSlicingType == SLICING_TYPE.MULTIPLANAR then
+         -- verifico che il primo piano sia sulla tavola, altrimenti lo aggiungo
+         if abs( vPoints[1]:getZ()) > GEO.EPS_SMALL or not AreSameVectorApprox( vNormals[1], Z_AX()) then
+            local ptP
+            local nRes, nPntCnt, nCrvCnt, nSrfCnt = EgtPlaneSurfTmInters( ORIG() + DELTAZ * Z_AX(), Z_AX(), nStmId, nGrpTmp, GDB_RT.GLOB)
+            if nSrfCnt > 0 then
+               ptP = EgtGP( nRes + nPntCnt + nCrvCnt, GDB_ID.ROOT) - DELTAZ * Z_AX()
+            else
+               for nCrvId = nRes + nPntCnt, nRes + nPntCnt + nCrvCnt - 1 do
+                  if EgtCurveIsClosed( nCrvId) then
+                     ptP = EgtGP( nCrvId, GDB_ID.ROOT) - DELTAZ * Z_AX()
+                     break
+                  end
+               end
+            end
+            table.insert( vPoints, 1, ptP)
+            table.insert( vNormals, 1, Z_AX())
+         end
+      end
+
+      local vCubicBezier = {}
+      for i = 1, #vPoints - 1 do
+         local dDist = 1/3 * dist( vPoints[i], vPoints[i+1])
+         local pt1 = vPoints[i] + dDist * vNormals[i]
+         local pt2 = vPoints[i+1] - dDist * vNormals[i+1]
+         vCubicBezier[i] = EgtCurveBezier( nGrpTmp, 3, { vPoints[i], pt1, pt2, vPoints[i+1]}, GDB_RT.GLOB) 
+      end
+      nSpineId = EgtCurveCompo( nAuxLayId, vCubicBezier)
+      EgtSetName( nSpineId or GDB_ID.NULL, SPINE_FROM_PLANES)
+   end
+   
+   EgtErase( nGrpTmp)
+   return nSpineId
+end
+
+---------------------------------------------------------------------
+local function ComputeMultiplanarSlicingData( dSliceStep, nMaxSlicesNbr, nSlicingType, nStmId)
+   -- le direzioni e i valori di slicing sono le normali e i punti che definiscono i piani di slicing e vengono calcolati sulla curva guida ( spine)
+   
+   -- recupero o calcolo la curva guida
+   local nSpineId = GetMultiplanarGuide( nStmId, nSlicingType)
    if not nSpineId or ( EgtGetType( nSpineId) & GDB_FY.GEO_CURVE) == 0 then
       EgtOutBox( "No spine for multiplanar slicing", 'Error', 'ERROR')
       return nil
@@ -1479,7 +1572,7 @@ function CalcSlices.Exec( nPartId, nStmId)
    local vSlicingVal = {}
    local vSlicingDir = {}
    if nSlicingType == SLICING_TYPE.MULTIPLANAR or nSlicingType == SLICING_TYPE.MULTIPLANAR_DEG45 or nSlicingType == SLICING_TYPE.MULTIPLANAR_HOR then
-      vSlicingVal, vSlicingDir = ComputeMultiplanarSlicingData( dSliceStep, nMaxSlicesNbr, nSlicingType)
+      vSlicingVal, vSlicingDir = ComputeMultiplanarSlicingData( dSliceStep, nMaxSlicesNbr, nSlicingType, nStmId)
    else
       vSlicingVal, vSlicingDir = ComputeSlicingData( vRefIds, vtSlicing, dSliceStep, dMaxH, nMaxSlicesNbr)
    end
diff --git a/LuaLibs/RunSlicing.lua b/LuaLibs/RunSlicing.lua
index 1a4ee24..bd83b45 100644
--- a/LuaLibs/RunSlicing.lua
+++ b/LuaLibs/RunSlicing.lua
@@ -86,6 +86,13 @@ local function RemoveOldSlices( nPartId)
       EgtErase( nExportGrpId)
    end
    
+   -- rimuovo spina per multiplanare calcolata dai piani
+   local nAuxGrpId = EgtGetFirstNameInGroup( nPartId, LAY_AUX)
+   local nSpineId = EgtGetFirstNameInGroup( nAuxGrpId, SPINE_FROM_PLANES)
+   if nSpineId then
+      EgtErase( nSpineId)
+   end
+   
 end
 
 ---------------------------------------------------------------------