Difference between revisions of "ParaView/Displaying Data"

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The goal of visualization is to generate representations of the data in
a visual form. In this chapter we will see different mechanisms available in
ParaView to look at the data to gain insight into it.
=Understanding Views=
When the ParaView application starts up, one sees a 3D viewport with
an axes at the center. This is a ''View''. In ParaView, ''Views'' are frames in
which the data can be ''seen''. There are different types of views. The default
view that shows up is a ''3D View'' which shows rendering of the geometry
extracted from the data or volumes or slices in a 3D scene. You can change the
default view '''Settings''' dialog (Edit | Settings (in case of Mac OS X,
ParaView | Preferences)).
There maybe parameters that are available to the user that control how the data
is displayed e.g. in case of 3D View, the data can be displayed as wireframes or
surfaces, you choose to change the color of the surface or use a scalar for
coloring etc. All these options are known as ''Display'' properties and are
accessible from the '''Display''' tab in the '''Object Inspector'''.
Since there can be multiple datasets shown in a view, as well as multiple views,
the '''Display''' tabs shows the properties for the active pipeline object
(changed by using the Pipeline browser, for example) in the active view.
==Multiple Views==
ParaView supports showing multiple views side by side. To create multiple views,
simply use the controls on the top-right corner of the view to split the frame
vertically or horizontally. You can even maximize a particular view to
temporarily hide other views. Once a view-frame is split, you will see a list of
buttons showing the different types of views that you can create to place in
that view. Simply click the button to create the view of your choice.
Some filters, such as '''Plot Over Line''' may automatically split the view
frame and show the data in a particular type of view suitable for the data
generated by the filter.
==Active View==
Once you have multiple views, the active view if indicated by a colored border
around the view frame. Several menus as well as toolbar buttons affect the
active view alone. Also they may become enabled/disabled based on whether that
corresponding action is supported by the active view.
The '''Display''' tab affects the active view. Similarly, the ''eye icon'' in
the '''Pipeline Browser''', next to the pipeline objects, indicates the visibility
state for that object in the active view.
When a new filter or source or reader is created, it will be displayed by
default in the active view, if possible (otherwise, if may create a new view).
=Types of Views=
In this section we will cover the different types of Views available in
ParaView. For each view, we will talk about the controls available to change the
view parameters using '''View Settings''' as well as the parameters associated
with the '''Display Tab''' for showing data in that view.
==3D View==
3D View is used to show the surface or volume rendering for the data in a 3D
world. This is the most commonly used view type.
When running in client-server mode, 3D View can render data either by bringing
the geometry to the client and then rendering it there or by rendering it on the
server (possibly in parallel) and then delivering the composited images to the
client. Refer to the '''Client-Server Visualization''' chapter for details.
Interacting with the 3D view will typically update the camera. This makes it
possible to explore the visualization scene. The default buttons are as follows,
they can be changed using the '''Application Settings''' dialog.
{| style="background-color:#ffffcc;" cellpadding="10" cellspacing="0" border="1"
!Left Button
!Middle Button
!Right Button
This view supports selection. One can select cells or points either on the
surface or those within a frustum. Selecting cells or points makes it possible
to extract those for further inspection or label them etc. Details about data
querying and selection can be found the Quantitative analysis chapter.
===View Settings===
The view settings dialog accessible through the Edit | View Settings menu or the
tool button on the left-corner of the view is used to change the view settings
per view.
This tab allows the user to choose the background color. One can use a solid
color or a gradient or even a background image.
By default the camera uses perspective projection. To switch to parallel
projection, check the "Use Parallel Projection" checkbox in this panel.
The 3D View requires lights to illumniate the geometry being rendered in the
scene. Once can control these lights using this pane.
The annotation pane enables controlling the visibility of the center axes and
the orientation widget. Users can also make the orientation widget interactive,
so that they can manually place the widget at location of their liking.
===Display Properties===
Users can control how the data from any source or filter is shown in this view
using the '''Display''' tab. In this section we will cover the various options
available to a user for controlling appearance of the rendering in the 3D view.
{| style="background-color:#ffffcc;" cellpadding="10" cellspacing="0" border="1"
| Visible
| Checkbox used to toggle the visibility of the data in the view. If it disabled, it implies that the data cannot be shown in this view.
| Selectable
| Checkbox used to toggle whether the data gets selected when using the selection mechanism for selecting and sub-setting data.
| Zoom to Data
| Click this button to zoom the camera so that the dataset is completely fits within the viewport.
The color group allows users to pick the scalar to color with or set a fixed
solid color for the rendering.
{| style="background-color:#ffffcc;" cellpadding="10" cellspacing="0" border="1"
| Interpolate Scalars
| If on, the scalars will be interpolated within polygons and the scalar mapping happens on per pixel basis. If off, then color mapping happens at points and colors are interpolated which is typically less accurate. This only affects when coloring with point arrays. Has no effect otherwise. This is disabled when coloring using a solid color.
| Map Scalars
| If the data array being color with can be directly interpreted as colors then one can uncheck this to not use any lookup table. Otherwise, when on, a lookup table will be used to map scalars to colors. This is disabled when the array is not of the type that can be interpreted as colors (i.e. vtkUnsignedCharArray).
| Apply Texture
| Makes is possible to apply a texture over the surface. This requires that the data has texture coordinates. One can use filters like '''Texture Map to Sphere''', '''Texture Map to Cylinder''' or '''Texture Map to Plane''' to generate texture coordinates when not present in the data. To load a texture, select '''Load''' from the combo-box which will popup a dialog allowing you to choose an image. Otherwise pick from already loaded textures listed in the combo-box.
| Color By
| This enables coloring of the surface/volume. Either choose the array to color with or set the solid color to use. When volume rendering, solid coloring is not possible, one has to choose the data array to volume render with.
| Set solid color
| Used to set the solid color. This is available only when '''Color By''' is set to use ''Solid Color''. ParaView defines a notion of a color palette consisting of different color categories. To choose a color from one of these predefined categories, click on the tiny arrow next to thus button. It will open up a drop down with options to choose from. If one uses a color from the palette, it possibly to globally change the color by changing the color palette e.g. for printing or for display on screen etc.
| Edit Color Map...
| One can edit the color-map or lookup table by clicking the Edit Color Map button. It's only shown when an array is chosen in the '''Color By''' combo-box.
The slice controls are available only for Image dataset (Uniform Rectilinear
Grids) when the representation type is '''Slice'''. The representation type is
controlled using the ''Style'' group on the '''Display''' tab.
These allow the user to pick the slice direction as well as the slice
Cube axes is a annotation box that can be used so show a scale around the
dataset. Use the '''Show cube axes''' checkbox to toggle its visibility. You can
further control the apperance of the cube axes by clicking '''Edit''' once the
cube-axes is visible.
{| style="background-color:#ffffcc;" cellpadding="10" cellspacing="0" border="1"
| Representation
| Use this to change how the data is represented i.e. as a surface, volume,
wireframe, points, or surface with edges.
| Interpolation
| Choose the method used to shade the geometry and interpolate point attributes.
| Point Size
| If your dataset contains points/vertices, this adjust the diameter of the rendered points. It also affects the point size when '''Representation''' is ''Points''.
| Line width
| If your dataset contains lines/edges, this scale adjust the width of the rendered lines. It also affects the rendered line width when '''Representation''' is ''Wireframe'' or ''Surface With Edges''.
| Opacity
| Set the opacity of the dataset's geometry. ParaView uses hardware-assisted Depth peeling, whenever possible, to remove artifacts due incorrect sorting order of rendered primitives.
| Volume Mapper
| When '''Representation''' is ''Volume'', this combo-box allows the user to choose a specific volume rendering technique. The techniques available change based on the type of the dataset.
| Set Edge Color
| This is available when '''Representation''' is ''Surface with Edgets''. It allows the user to pick the color to use for the edges rendered over the surface.
====Backface Style====
This allows the user to define backface properties. In computer graphics, backface refers to the face of a geometric primitive with the normal point away from the camera. Users can choose to hide the backface or front face or specify different characteristics for the two faces using these settings.
These settings allow the user to transform the rendered geometry, without actually transforming the data. Note that since this transformation happens during rendering, any filters that you apply to this data-source, will still be working on the original, untransformed data. Use the '''Transform''' filter if you want to transform the data instead.
==2D View==
2D View is similar to 3D view except that it can only show slices from uniform
grid datasets i.e. volume datasets or image datasets.
The interaction is also limited to a 2D plane i.e. rotation is not available. Currently this view does not support selection. That will be supported in future releases.
When one loads a 2D image, ParaView by default creates this view.
Since this view is same as the 3D view, it has the same features when it comes to client-server and parallel rendering.
Interactions with this view update the camera.  The default buttons are as follows, they can be changed using the '''Application Settings''' dialog.
{| style="background-color:#ffffcc;" cellpadding="10" cellspacing="0" border="1"
!Left Button
!Middle Button
!Right Button
Unlike 3D view, this view currently does not support selection. However, that support will be added in future.
===View Settings===
The view settings dialog accessible through the Edit | View Settings menu or the tool button on the left-corner of the view is used to change the view settings per view.
[[File:ParaViewUsersGuide2DViewSettings.png|300px|View settings dialog for the 2D View]]
The user can change the background color and toggle the visibility of the axes-box.
[[File:ParaViewUsersGuide2DViewAxes.png|300px|2D View showing the axes-box]]
===Display Properties===
Display tab for this view is exactly same as the 3D View, except that some options may be unavailable such as changing of representation type.
==Spreadsheet View==
Spreadsheet View is used to inspect the raw data in a spreadsheet. When running
in client-server mode, to avoid delivering the entire dataset to the client for
displaying the spreadsheet (since the data can be very large), this view streams
only visible chunks of the data to the client. As the user scrolls around the
spreadsheet, new data chunks are fetched.
Unlike some other views, this view can only show one dataset at a time. For
composite datasets, it shows only one block at a time. One can pick the block
to show using the '''Display''' tab.
As far as the usability is concerned, this view behaves exactly like typical spreadsheets shown in applications like Microsoft's Excel or Apple's Pages:
* One can scroll up and down to inspect new rows.
* One can sort any column by clicking on the header for the column. Repeated clicking on the column header toggles the sorting order. When running in parallel, ParaView uses sophisticated parallel sorting algorithms to avoid memory and communication overheads to sort large, distributed datasets.
* One can double-click on a column header to toggle a mode in which only that column is visible. This reduces clutter when one is interested in a single attribute array.
* One can click on rows to select the corresponding elements i.e. cells or points. This is not available when in "Show selected only mode" (explained later). Also, when one creates a selection in other views e.g. the 3D view, the rows corresponding to the selected elements will be highlighted.
Unlike other views, Spreadsheet View has a header. This header provides quick access to some of the commonly used functionality in this view.
[[File:ParaViewUsersGuideSpreadsheetViewHeader.png|400px|Spreadsheet View Header]]
* Since this view can only show one dataset at a time, one can quickly choose the dataset to show using the '''Showing''' combo-box.
* One can choose the attribute type i.e. point attributes, cell attributes, to display using the '''Attribute''' combo-box.
* '''Precision''' controls the number of digits to show after decimal point for floating point numbers.
* The last push-button allows the user to enter the view in a mode where it only shows the selected rows. This is useful when one creates a selection using another view such as the 3D view and wants to inspect the details for the selected cells/points.
===View Settings===
Currently, no user settable settings are available for this view.
===Display Properties===
The display properties for this view provide the same functionality as the header. Additionally, when dealing with composite datasets, the display tab shows a widget allowing the user to choose the block to display in the view.
==Line Chart View==
A traditional 2D line plot is often the best option to show trends in small quantities of data. A line plot is also a good choice to examine relationships between different data values that vary over the same domain.
Any reader, source, or filter that produces plottable data can be displayed in an XY Plot View. ParaView stores its plottable data in table (vtkTable). Using the display properties, users can choose which columns in the table must be plotted on the x and y axes.
As with the other view types, exactly what is displayed in the active XY Plot View is displayed by, and controllable with, the eye icons in the Pipeline Browser panel. When an XY Plot View is active, only those filters that produce plotable output have eye icons.
The XY Plot View is the preferred View type for the Plot over Line, Plot Point over Time, Plot Cell over Time, Plot Field Variable over Time, and Probe Location over Time filters. Creating any one of these filters will automatically create an XY Plot View for displaying its output. Figure 3 shows a plot of the data values within a volume as they vary along three separate paths. The top curve comes from the line running across the center of the volume, where the largest values lie. The other two curves come from lines running near the edges of the volume.
Unlike the 3D and 2D render view, the charting views are client-side views i.e. they deliver the data to be plotted to the client. Hence ParaView only allows results from some standard filters such as '''Plot over Line''' in the line chart view by default. However it is also possible to plot cell or point data arrays for any dataset by apply the '''Plot Data''' filter.
Line chart view supports the following interaction modes:
* Right-click and drag to pan
* Left-click and drag to select
* Middle-click and drag to zoom to region drawn
To reset the view, use the '''Reset Camera''' [[Image:ParaViewUsersGuideResetCamera.png]] button in the '''Camera Toolbar'''.
===View Settings===
The '''View Settings''' for Line Chart enable the user to control the appearance of the chart including titles, axes positions etc. There are several pages available in this dialog. The '''General''' page controls the overall appearance of the chart, while the other pages controls the appearance of each of the axes.
====General Settings Page====
This page allows users to change the title and legend. One can change the title text. To show the current animation time in the title text, simply use the keyword ''${TIME}''. Users can further change the font and alignment for the title.
This page also enable changing the appearance and positioning of the legend.
====Axis Settings Page====
This page allows changing the properties of a particular axis. Four pages are provided for each of the axes. By clicking on the name of the axis, one can access the settings page for the corresponding axes.
* Axis
** '''Show Axis''' : controls the axis visibility.
** '''Show Axis Grid''': controls whether a grid is to be drawn perpendicular to this axis.
** '''Colors''': enables changing the axis as well as the grid color.
* Labels
** '''Show Axis Labels When Space is Available''' : controls label visibility along this axis.
** '''Font''' and '''Color''': enables changing the label font and color.
** '''Notation''': allows user to choose between '''Mixed''', '''Scientific''' and '''Fixed''' point notations for numbers.
** '''Precision''': controls precision after '.' in '''Scientific''' and '''Fixed''' notations.
====Axis Layout Page====
This page allows the user to change the axis range and scale.
* '''Use Logarithmic Scale When Available''': check this to use a log scale unless the data contains numbers <= 0.
* '''Let the Chart Determine the Axis Layout''': pick this radio button to let the chart use the optimal range and spacing for this axis.
* '''Specify the Axis Range''': pick this radio button to specify the axis range explicitly. The labels are auto-placed within this range.
* '''Specify Each of the Axis Labels''': pick this radio button to specify each label location on axis explicitly.
====Axis Title Page====
This page allows the user to change the title for the axis. One can change the text as well as color and font for the axis title.
===Display Properties===
==Bar Chart View==
===View Settings===
===Display Properties===

Latest revision as of 18:36, 14 January 2015

The Users Guide has been moved from the Wiki to The ParaView Guide. Please use the history if you want to access the old version of this document.