Updating PipelineReuse

src/PythonicAPI.md

@@ -70,6 +70,7 @@ This Python script, [SelectExamples](../Python/Utilities/SelectExamples), will l
 | Example Name | Description | Image |
 | -------------- | ------------- | ------- |
 [GeometricObjectsDemo](/PythonicAPI/GeometricObjects/GeometricObjectsDemo) |
+[PipelineReuse](/PythonicAPI/GeometricObjects/PipelineReuse) | How to reuse a pipeline.
 [SourceObjectsDemo](/PythonicAPI/GeometricObjects/SourceObjectsDemo) | Examples of source objects that procedurally generate polygonal models.  These nine images represent just some of the capability of VTK. From upper left in reading order: sphere, cone, cylinder, cube, plane, text, random point cloud, disk (with or without hole), and line source. Other polygonal source objects are available; check subclasses of vtkPolyDataAlgorithm.
 
 ### Cells

src/PythonicAPI/GeometricObjects/PipelineReuse.py

@@ -6,67 +6,46 @@ import vtkmodules.vtkInteractionStyle
 import vtkmodules.vtkRenderingOpenGL2
 from vtkmodules.vtkCommonColor import vtkNamedColors
 from vtkmodules.vtkFiltersCore import (
+    vtkAppendPolyData,
     vtkElevationFilter,
     vtkPolyDataNormals,
 )
 from vtkmodules.vtkFiltersSources import (
     vtkConeSource,
-    vtkCylinderSource
+    vtkCylinderSource,
 )
 from vtkmodules.vtkRenderingCore import (
     vtkActor,
     vtkPolyDataMapper,
+    vtkRenderer,
     vtkRenderWindow,
     vtkRenderWindowInteractor,
-    vtkRenderer
 )
 
 
 def main():
     colors = vtkNamedColors()
 
-    # extraction_mode = {'point_seeded_regions': 1, 'cell_seeded_regions': 2, 'specified_regions': 3, 'largest_region': 4,
-    #                    'all_regions': 5, 'closest_point_region': 6}
-    # pipeline = (
-    #         vtkElevationFilter()
-    #         >> vtkShrinkFilter()
-    #         >> vtkGeometryFilter()
-    #         >> vtkPolyDataConnectivityFilter(color_regions=True, extraction_mode=extraction_mode['all_regions'])
-    #         >> vtkPolyDataNormals()
-    # )
-    p1 = (
-            vtkElevationFilter(low_point=(0, -2, 2), high_point=(0, 3, 2))
+    p = (
+            vtkElevationFilter(low_point=(0, -2.5, 0), high_point=(0, 3.5, 0))
             >> vtkPolyDataNormals()
     )
-    p2 = (
-            vtkElevationFilter(low_point=(0, -2, 2), high_point=(0, 3, 2))
-            >> vtkPolyDataNormals()
-    )
-
-    cone = vtkConeSource(radius=5, resolution=8, height=2, direction=(0, 1, 0), center=(0, 1.5001, 0))
-    cone_mapper = vtkPolyDataMapper()
-    cone_actor = vtkActor(mapper=cone_mapper)
 
+    cone = vtkConeSource(radius=5, resolution=8, height=3, direction=(0, 1, 0), center=(0, 2.0, 0))
     cylinder = vtkCylinderSource(radius=6, resolution=9, height=3, center=(0, -1, 0))
-    cylinder_mapper = vtkPolyDataMapper()
-    cylinder_actor = vtkActor(mapper=cylinder_mapper)
 
-    # This works since p1 and p2 are separate pipelines.
-    cone >> p1 >> cone_mapper
-    cylinder >> p2 >> cylinder_mapper
+    append = vtkAppendPolyData()
+    mapper = vtkPolyDataMapper()
+    actor = vtkActor(mapper=mapper)
 
-    # Only the cylinder is mapped because whilst p1 is assigned to p2, it is, in fact, p1.
-    # p2 = p1
-    # Will not work because update() is the same as update().output.
-    # p2 = p1.update()
-    # AttributeError: 'Pipeline' object has no attribute 'DeepCopy'
-    # p2 = p1.DeepCopy()
-    #
-    # cylinder >> p2 >> cylinder_mapper
+    # Here we use the pipeline in a functional way. This allows us to reuse the pipeline.
+    # p(cone()) returns a data object detached from the pipeline so any changes to the pipeline
+    # afterward would not be automatically propagated to the rendering pipeline.
+    # Finally, we use an append filter to combine the cone and cylinder.
+    (p(cone()), p(cylinder())) >> append >> mapper
 
     ren = vtkRenderer(background=colors.GetColor3d('DimGray'))
-    ren.AddActor(cone_actor)
-    ren.AddActor(cylinder_actor)
+    ren.AddActor(actor)
 
     ren_win = vtkRenderWindow(size=[600, 600], window_name='PipelineReuse')
     ren_win.AddRenderer(ren)

src/PythonicAPIComments.md

@@ -104,3 +104,22 @@ Sometimes we need to update part of a pipeline so that output can be used in oth
 | -------------- | ---------------------- | ------- |
 [LineOnMesh](/PythonicAPI/DataManipulation/LineOnMesh) | One pipeline creates a smoothed dataset. However we need to update `smooth_loop` in the pipeline so that `?vtkCellLocator?` finds cells in order to create the spline.
 [MeshLabelImageColor](/PythonicAPI/DataManipulation/MeshLabelImageColor) | We need the smoother error for the scalar range in the mapper. So we create the pipeline and update `smoother` to get the needed scalar range. Of course, all other pipeline elements feeding into `smoother` will be updated also.
+
+## Reusing a pipeline
+
+Pipelines can be reused.
+
+``` Python
+    # The pipeline to reuse.
+    p = (a >> b >> c)
+    # Sources for the pipeline.
+    s1 = d
+    s2 = e
+    # Use the pipeline in a functional way.
+    p1 = p(s1())
+    p2 = p(ss())
+```
+
+| Example Name | Comments | Image |
+| -------------- | ---------------------- | ------- |
+[PipelineReuse](/PythonicAPI/GeometricObjects/PipelineReuse) | Here we use the pipeline in a functional way. This allows us to reuse the pipeline, here, p(cone()) returns a data object so any changes to the pipeline afterward would not be automatically propagated to the rendering pipeline. Finally, we use an append filter to combine the cone and cylinder.