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90 lines
3.9 KiB
Markdown
90 lines
3.9 KiB
Markdown
Implementation Details: Slice View {#DesignSliceView}
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===================================
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[TOC]
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This page summarizes the design details of what ParaView calls the **Slice
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View** (sometimes called the **Multi-Slice View** since it allows the users to
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add multiple slices).
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##Classes##
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Let's start by getting an overview of the new classes added for supporting this
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Slice view.
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vtkSMMultiSliceViewProxy is the view-proxy. It's a vtkSMRenderViewProxy
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subclass. This makes it possible for the application to treat this as simply a
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specialization of the *Render View*, which it indeed is. Thus all toolbars for
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setting axis of rotation, camera positions, selection etc. will continue to
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work.
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pqMultiSliceView is the pqRenderView subclass created by the GUI whenever it
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encounters a vtkSMMultiSliceViewProxy. The extra thing that this class does it
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manage the UI components to allow the user to interactively place slices in the
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view. Use pqMultiSliceAxisWidget, this class updates the *XSlicesValues*,
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*YSlicesValues*, and *ZSlicesValues* properties on the vtkSMMultiSliceViewProxy
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proxy.
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vtkPVMultiSliceView is a VTK-object controlled by the
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vtkSMMultiSliceViewProxy. vtkPVMultiSliceView is a indeed a vtkPVRenderView
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subclass. It adds API to set/get the slice positions along each of the
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coordinate axes. Representations that want to respect the slices specified by
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this view can access the view in vtkPVView::REQUEST_UPDATE() pass to get the
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slice positions. This pass will indeed be triggered on all data-server ranks
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after the slice positions have been changed.
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vtkGeometrySliceRepresentation is a vtkGeometryRepresentation subclass which is
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used to add a new **Slices** representation type to the standard
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*GeometryRepresentation* proxy.
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vtkSMMultiSliceViewProxy::GetRepresentationType() will suggest creating of this
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extended *GeometryRepresentation*, know as
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(*representations*, *CompositeMultiSliceRepresentation*) to the ProxyManager.
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*CompositeMultiSliceRepresentation* supports the usual representation-types e.g.
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Surface, Wireframe, etc. along with the new *Slices* type. Whenever the user
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picks the *Slices* representation-type, the vtkGeometrySliceRepresentation will
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be used.
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vtkGeometrySliceRepresentation works with vtkPVMultiSliceView to display any
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dataset as a set of slices along the coordinate planes. The slice positions are
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obtained from vtkPVMultiSliceView in the vtkPVView::REQUEST_UPDATE().
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vtkGeometrySliceRepresentation works by replacing the vtkPVGeometryFilter (in
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vtkGeometryRepresentation) with an internal vtkPVGeometryFilter subclass that
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extracts the slices from the input dataset before passing it to the
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vtkPVGeometryFilter implementation. It uses the vtkThreeSliceFilter to apply a
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collection of slice filters in one go.
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##Supporting Miscellaneous Use-Cases##
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Let's look at how we support a bunch of miscellaneous use-cases.
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###Choosing *Slices* representation by default###
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**Use-Case**: When user shows a new dataset in this Slice view, we want the
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default representation-type to be "Slices", and not "Surface" or anything
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that vtkSMRepresentationTypeDomain picks.
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**Solution (HACK)**: vtkSMMultiSliceViewProxy::CreateDefaultRepresentation()
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changes the *Representation* property's value to *Slices*. Further more, to
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avoid vtkSMParaViewPipelineController::PostInitializeProxy() from resetting the
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property value to domain-defaults (using
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vtkSMProperty::ResetToDomainDefaults()), we add an XML hint to the property.
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This is done in vtkSMMultiSliceViewProxy::ForceRepresentationType().
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###Setting default slice locations###
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**Use-Case**: When a new dataset is shown in this view, we want the view to
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automatically place slices at the center of the dataset.
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**Solution (HACK)**: We set the properties on the view in
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vtkSMMultiSliceViewProxy::CreateDefaultRepresentation(). Currently the
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properties on the view are changed only when there are no slices specified
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already.
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Notes
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------
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This page is generated from *MultiSliceView.md*.
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