Trac #20109: Add pictures to plot3d.py

Patch to add pictures generated using .. PLOT:: to the plot3d.py file

URL: http://trac.sagemath.org/20109
Reported by: jhonrubia6
Ticket author(s): Javier Honrubia Gonzalez
Reviewer(s): Dima Pasechnik

src/sage/plot/plot3d/base.pyx

@@ -494,7 +494,6 @@ cdef class Graphics3d(SageObject):
                 a_max[i] = a_max[i] + 1
         return a_min, a_max
 
-
     def bounding_box(self):
         """
         Return the lower and upper corners of a 3d bounding box for ``self``.
@@ -1735,6 +1734,20 @@ end_scene""" % (render_params.antialiasing,
         string_list += ['</volume></mesh></object></amf>']
         return "".join(string_list)
 
+    def plot(self):
+        """
+        Draw a 3D plot of this graphics object, which just returns this
+        object since this is already a 3D graphics object.
+        Needed to support PLOT in doctrings, see :trac:`17498`
+
+        EXAMPLES::
+
+            sage: S = sphere((0,0,0), 2)
+            sage: S.plot() is S
+            True
+
+        """
+        return self
 
 # if you add any default parameters you must update some code below
 SHOW_DEFAULTS = {'viewer': 'jmol',

src/sage/plot/plot3d/parametric_surface.pyx

@@ -518,7 +518,6 @@ cdef class ParametricSurface(IndexFaceSet):
 
         self.render_grid = urange, vrange
 
-
     def get_grid(self, ds):
         """
         TEST::
@@ -673,6 +672,20 @@ cdef class ParametricSurface(IndexFaceSet):
         """
         raise NotImplementedError
 
+    def plot(self):
+        """
+        Draw a 3D plot of this graphics object, which just returns this
+        object since this is already a 3D graphics object.
+        Needed to support PLOT in doctrings, see :trac:`17498`
+        
+        EXAMPLES::
+
+            sage: S = parametric_plot3d( (sin, cos, lambda u: u/10), (0, 20))
+            sage: S.plot() is S
+            True
+
+        """
+        return self
 
 class MoebiusStrip(ParametricSurface):
     """