Merge pull request #328 from HEXRD/angular-pixel-size-update

swith to using pixel angular gradient arrays

hexrd/instrument.py

@@ -365,6 +365,13 @@ def _solid_angle_of_triangle(vtx_list):
 
         return 2.*np.arctan2(scalar_triple_product, denominator)
 
+
+def _fix_branch_cut_in_gradients(pgarray):
+    return np.min(
+        np.abs(np.stack([pgarray - np.pi, pgarray, pgarray + np.pi])),
+        axis=0
+    )
+
 # =============================================================================
 # CLASSES
 # =============================================================================
@@ -2402,30 +2409,17 @@ def pixel_tth_gradient(self, origin=ct.zeros_3):
         return np.linalg.norm(np.stack(np.gradient(ptth)), axis=0)
 
     def pixel_eta_gradient(self, origin=ct.zeros_3):
-        period = np.r_[0., 2*np.pi]
         assert len(origin) == 3, "origin must have 3 elemnts"
         _, peta = self.pixel_angles(origin=origin)
 
-        # !!! handle cyclic nature of eta
-        rowmap = np.empty_like(peta)
-        for i in range(rowmap.shape[0]):
-            rowmap[i, :] = mapAngle(
-                peta[i, :], peta[i, 0] + period
-            )
-
-        colmap = np.empty_like(peta)
-        for i in range(colmap.shape[1]):
-            colmap[:, i] = mapAngle(
-                peta[:, i], peta[0, i] + period
-            )
+        peta_grad_row = np.gradient(peta, axis=0)
+        peta_grad_col = np.gradient(peta, axis=1)
 
-        peta_grad_row = np.gradient(rowmap)
-        peta_grad_col = np.gradient(colmap)
+        # !!!: fix branch cut
+        peta_grad_row = _fix_branch_cut_in_gradients(peta_grad_row)
+        peta_grad_col = _fix_branch_cut_in_gradients(peta_grad_col)
 
-        return np.linalg.norm(
-            np.stack([peta_grad_col[0], peta_grad_row[1]]),
-            axis=0
-        )
+        return np.linalg.norm(np.stack([peta_grad_col, peta_grad_row]), axis=0)
 
     def cartToPixel(self, xy_det, pixels=False):
         """
@@ -2467,7 +2461,9 @@ def pixelToCart(self, ij_det):
 
     def angularPixelSize(self, xy, rMat_s=None, tVec_s=None, tVec_c=None):
         """
-        Wraps xrdutil.angularPixelSize
+        Notes
+        -----
+        !!! assumes xy are in raw (distorted) frame, if applicable
         """
         # munge kwargs
         if rMat_s is None:
@@ -2476,7 +2472,19 @@ def angularPixelSize(self, xy, rMat_s=None, tVec_s=None, tVec_c=None):
             tVec_s = ct.zeros_3x1
         if tVec_c is None:
             tVec_c = ct.zeros_3x1
+        origin = np.dot(rMat_s, tVec_c).flatten() + tVec_s.flatten()
+
+        # FIXME: perhaps not necessary, but safe...
+        xy = np.atleast_2d(xy)
+
+        # get pixel indices
+        i_crds = cellIndices(self.row_edge_vec, xy[:, 1])
+        j_crds = cellIndices(self.col_edge_vec, xy[:, 0])
 
+        ptth_grad = self.pixel_tth_gradient(origin=origin)[i_crds, j_crds]
+        peta_grad = self.pixel_eta_gradient(origin=origin)[i_crds, j_crds]
+
+        '''
         # call function
         ang_ps = xrdutil.angularPixelSize(
             xy, (self.pixel_size_row, self.pixel_size_col),
@@ -2485,6 +2493,8 @@ def angularPixelSize(self, xy, rMat_s=None, tVec_s=None, tVec_c=None):
             distortion=self.distortion,
             beamVec=self.bvec, etaVec=self.evec)
         return ang_ps
+        '''
+        return np.vstack([ptth_grad, peta_grad]).T
 
     def clip_to_panel(self, xy, buffer_edges=True):
         """
@@ -3817,7 +3827,7 @@ def _lorentz_polarization_factor(tth, eta, f_hor, f_vert, unpolarized):
     L = 1./(4.0*cth*sth2)
     if unpolarized:
         P = (1. + ctth2)/2.
-    else:    
+    else:
         P = f_hor*(seta2 + ceta2*ctth2) + f_vert*(ceta2 + seta2*ctth2)
 
     return L*P