VisIt-tutorial-basics

From VisItusers.org

Contents 1 Starting VisIt 2 What you see 3 Opening files 3.1 Advanced file opening features 4 Making a plot 5 Modifying the Plot attributes 6 Applying an operator 7 VisIt interaction modes 8 Other plots 9 Other operators 10 Saving an image 11 Saving a database 12 Subsetting

[edit] Starting VisIt

The way you start VisIt depends on the platform you are on:

• On Windows, double click on the VisIt icon
• On Unix & Mac, invoke: /path/to/visit/bin/visit
  • Most people ultimately put /path/to/visit/bin in their $PATH and then just say "visit".

[edit] What you see

• The tall grey window on the left is called the "GUI". It is the primary mechanism for driving VisIt.
• The window on the right is called the "viewer". It displays results.

[edit] Opening files

The first thing to do is to select and open files.

1. Go to the GUI and find File->Select File.
2. Change the "Path" field to be "/path/to/visit/data"
3. Click "Remove all" to clear out the files from the directory you started VisIt in.
4. Click "Select all" to select all of the files in the "data" directory.
5. Click "OK" on the bottom right.
6. The top part of the GUI has a heading labeled "Selected files". This will now contain the files from the "data" directory.
7. Highlight the file "noise.silo" and then click "Open"
   • You can also double click noise.silo and will automatically open it.

You've opened a file!

[edit] Advanced file opening features

1. In the file selection window:
   • There is a field for "host". That is how you run client/server
   • There is a "filter". That is provided to subset the file list to only the files VisIt may want.
     • Example filter: "*.silo *.vtk"
2. There is another mechanism for opening files under File->Open that opens a single file.
   • This allows you to explicitly tell VisIt what type of file it is opening.
   • VisIt uses heuristics otherwise (which are often successful).
3. You can also open files on the command line: "visit -o file.ext"

[edit] Making a plot

1. Go to Plots->Pseudocolor->hardyglobal.
   • On Windows & Unix: the plots header is located two thirds of the way down the gui.
   • On the Mac: the plots header is located along the top pulldown.
2. You will see a green entry added the "Active plots list", which is located half way down the gui.
   • This means VisIt will draw this plot after you click "Draw"
3. Click draw.
4. You should see a plot appear in the visualization window.
5. Go to Plots->Mesh->Mesh
6. Click draw.
7. You should now see both a Pseudocolor and plot mesh.
8. Highlight the Pseudocolor plot in the active plots list.
9. Click "Hide/Show"
   • (This will hide the Pseudocolor plot ... you should now see only the mesh plot.)
10. Highlight the mesh plot and click Delete.
    • You should now have an empty window.
    • The Pseudocolor plot should now be selected.
11. Click "Hide/Show"
    • The Pseudocolor plot should reappear.

[edit] Modifying the Plot attributes

1. Go to Plot Attributes->Pseudocolor.
   • This should bring up a window for modifying the plot.
2. Change the scale from "Linear" to "Log"
3. Click Apply.
   • (The colors changed)
4. Click "Min" on and change the min to 3.
5. Click "Max" on and change the max to 4.
6. Click Apply.
   • (The colors change again.)
7. Change the opacity to be 50%.
8. Click Apply.
   • (You can now see through the plot. Note that you only see the external faces. If you want to see the data from the whole volume, that will be with the volume plot.)
9. Change back the scale, limits, and opacity back to their original settings and click Apply.
10. Dismiss the Pseudocolor plots window.

[edit] Applying an operator

1. Go to Operators->Slice
   • Operators is located next to Plots.
2. You are now looking at a 2D slice.
3. Go to Operator Attributes->Slice.
4. There are many controls for setting the slice plane ... play with them.
5. Operators can be removed by clicking on an expansion arrow in the plots list, then clicking on the red X icon next to an operator.

[edit] VisIt interaction modes

There are five basic interaction modes:

1. Navigate
2. Zone-pick
3. Node-pick
4. Zoom
5. Lineout

You always start in Navigate. Navigate allows you to pan and rotate the data set.

1. Put the cursor in the visualization window from the viewer.
2. Left click (or single click if you do not have a 3 button mouse) and move the mouse.
3. The data set will pan with the mouse.
   • In 3D, the data set rotates.

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1. The interaction mode is controlled by the toolbar, which is located at the top of the visualization window.
2. The five interaction modes are all located together on the toolbar, towards the bottom.
   • Navigate is represented by a compass and should be indented.
3. Click on the magnifying glass , which corresponds to zoom.
4. Go to the visualization window and left click (single click) and HOLD IT DOWN.
5. Move the mouse a bit.
   • You should see a rubber band.
6. Lift up the mouse button.
   • You should now be zoomed in so that the viewport matches what was previously inside the rubber band.

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1. Find the icon of a camera that has a green "X" around it. (The camera is mostly obscured by the X)
2. Click it.
   • This will reset your view.
3. Click the icon next to the magnifying glass, which has red, blue, and black lines.
   • This is for lineout.
4. Put the cursor over the data and left click (single click) and HOLD IT DOWN.
5. Move the mouse a bit.
   • You should see a single line moving around.
6. Lift up the mouse button.
7. The window layout changes. You now have two windows. The first window is the same, but the second now contains a "Lineout", which has hardyglobal as a function of distance over the line.
8. On the window that has the curve, find the icon on the toolbar of the window with a red circle with a line through it.
9. Click this button.
   • The new window should disappear.

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1. (You should only have one window now.)
2. Click on the icon that has a '+' with a small Z. This is "zone-pick".
3. Put the cursor over the data set and left click (single click).
4. This will bring up a new window ... the pick window.
   • The pick window contains information about the zone (i.e. cell or element) that you just picked in.
5. The pick contains variable information, intersection location, zone ID, and IDs of incident nodes (i.e. point or vertex).

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Pick can return a lot more information than it did.

1. Go to the Variables tab and add "shepardglobal"
2. Turn on "Physical Coords" under "Display for Nodes"
3. Turn on "Domain-Logical" under "Display for Zones"
4. Click apply.
5. Make another pick.
6. You get info about shepardglobal, the coordinates of each node, and the logical coordinates for the zone.

[edit] Other plots

1. We will experiment with the Contour, Filled Boundary, Label, Vector and Volume plots.

[edit] Other operators

1. We will experiment with the Clip and Threshold operators.

[edit] Saving an image

1. With a current plot, go to File->Save Window.
   • This saves an image to the filesystem.

[edit] Saving a database

VisIt can be part of a larger tool chain.

1. If you do not already have one, make a Pseudocolor plot of hardyglobal from the noise.silo database.
2. Apply the Threshold operator and change the range to be 3->max.
3. Draw.
4. Go to File->Export Database.
5. Change the file type to VTK
6. Export.
   • A file named visit_ex_db.vtk has been saved to the file system.

[edit] Subsetting

1. Delete any plots in your window.
2. Open up multi_ucd3d.silo
3. Make a Subset plot of "domains(mesh1)"
   • The plot is colored by "domains", which normally correspond to a simulation's processors.
4. In the active plots list, find the four interlocking rings and click on it.
5. This will bring up the Subset window.
6. Turn off some domains and click apply
   • You will see some of the domains disappear.
   • (Subsetting works with any plot type.)
7. Turn all the domains back on.
8. Turn off materials 1 and 3.
   • You will see material 2 only, colored by domain.

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This mechanism is used to expose subsetting for materials, domains, AMR levels, and other custom subsettable parts.