calculate default depth for off axis proj initially

yt/visualization/fixed_resolution.py

@@ -639,7 +639,6 @@ def _generate_image_and_mask(self, item) -> None:
                 self.bounds[5] - self.bounds[4],
             )
         )
-        depth = dd.depth[0] if dd.depth is not None else None
         buff = off_axis_projection(
             dd.dd,
             dd.center,
@@ -652,7 +651,7 @@ def _generate_image_and_mask(self, item) -> None:
             no_ghost=dd.no_ghost,
             interpolated=dd.interpolated,
             north_vector=dd.north_vector,
-            depth=depth,
+            depth=dd.depth,
             method=dd.method,
         )
         if self.data_source.moment == 2:

yt/visualization/plot_window.py

@@ -83,7 +83,11 @@ def get_window_parameters(axis, center, width, ds):
 
 
 def get_oblique_window_parameters(
-    normal, center, width, ds, depth=None, get3bounds=False
+    normal,
+    center,
+    width,
+    ds,
+    depth=None,
 ):
     center, display_center = ds.coordinates.sanitize_center(center, axis=None)
     width = ds.coordinates.sanitize_width(normal, width, depth)
@@ -101,15 +105,7 @@ def get_oblique_window_parameters(
 
     w = tuple(el.in_units("code_length") for el in width)
     bounds = tuple(((2 * (i % 2)) - 1) * w[i // 2] / 2 for i in range(len(w) * 2))
-    if get3bounds and depth is None:
-        # off-axis projection, depth not specified
-        # -> set 'large enough' depth using half the box diagonal + margin
-        d2 = ds.domain_width[0].in_units("code_length") ** 2
-        d2 += ds.domain_width[1].in_units("code_length") ** 2
-        d2 += ds.domain_width[2].in_units("code_length") ** 2
-        diag = np.sqrt(d2)
-        bounds = bounds + (-0.51 * diag, 0.51 * diag)
-    return (bounds, center)
+    return bounds, center
 
 
 def get_axes_unit(width, ds):
@@ -2389,7 +2385,8 @@ class OffAxisProjectionPlot(ProjectionPlot, PWViewerMPL):
     depth : A tuple or a float
         A tuple containing the depth to project through and the string
         key of the unit: (width, 'unit'). If set to a float, code units
-        are assumed
+        are assumed. In not set, then a depth equal to the diagonal of
+        the domain width plus a small margin will be used.
     weight_field : string
         The name of the weighting field.  Set to None for no weight.
     max_level: int
@@ -2466,6 +2463,13 @@ def __init__(
                 "currently supported geometries:"
                 f" {self._supported_geometries!r}"
             )
+
+        if depth is None:
+            # off-axis projection, depth not specified
+            # -> set 'large enough' depth using half the box diagonal + margin
+            depth = np.sqrt(np.sum(ds.domain_width.in_units("code_length") ** 2)) * 1.02
+        depth = ds.coordinates.sanitize_depth(depth)[0]
+
         # center_rot normalizes the center to (0,0),
         # units match bounds
         # for SPH data, we want to input the original center
@@ -2479,7 +2483,6 @@ def __init__(
             width,
             ds,
             depth=depth,
-            get3bounds=True,
         )
         # will probably fail if you try to project an SPH and non-SPH
         # field in a single call