Geant4手册目录
Geant4: 8.4.  Controlling Visualization from Commands

8.4.  Controlling Visualization from Commands

This section describes just a few of the more commonly used visualization commands. For the complete list of commands and options, see the Control...UICommands section of this user guide.

For simplicity, this section assumes that the Geant4 executable was compiled incorporating the DAWNFILE and the OpenGL-Xlib drivers. For details on creating an executable for visualization see Section 8.2.

8.4.1.  Scene, scene handler, and viewer

In using the visualization commands, it is useful to know the concept of "scene", "scene handler", and "viewer". A "scene" is a set of visualizable raw 3D data. A "scene handler" is a graphics-data modeler, which processes raw data in a scene for later visualization. And a "viewer" generates images based on data processed by a scene handler. Roughly speaking, a set of a scene handler and a viewer corresponds to a visualization driver.

The steps of performing Geant4 visualization are explained below, though some of these steps may be done for you so that in practice you may use as few as just two commands (such as /vis/open OGLIX plus /vis/drawVolume). The seven steps of visualization are:

Step   Command Alternative command
1 Create a scene handler and a viewer /vis/sceneHandler/create /vis/open
/vis/viewer/create
2 Create an empty scene /vis/scene/create /vis/drawVolume
3 Add raw 3D data to the created scene /vis/scene/add/volume
4 Attach the current scene to the current scene handler /vis/sceneHandler/attach
5 Set camera parameters, drawing style (wireframe/surface), etc E.g., /vis/viewer/set/viewpoint  
6 Make the viewer execute visualization /vis/viewer/refresh  
7 Declare the end of visualization for flushing /vis/viewer/flush  

For details about the commands, see below.

These seven steps can be controlled explicitly to create multiple scenes and multiple viewers, each with its own set of parameters, with easy switching from one scene to another. But for the most common case of just having one scene and one viewer, many steps are handled implicitly for you.

8.4.2.  Create a scene handler and a viewer: /vis/open command

Command "/vis/open" creates a scene handler and a viewer, which corresponds to Step 1.

Command: /vis/open [driver_tag_name]

  • Argument

    A name of (a mode of) an available visualization driver.

  • Action

    Create a visualization driver, i.e. a set of a scene hander and a viewer.

  • Example: Create an OpenGL generic driver with its immediate mode

    Idle> /vis/open OGLI

  • Additional notes

    For immediate viewers, such as OGLI, your geometry will immediately be rendered in the new GL window

How to list available driver_tag_name:

Idle> help /vis/open

or

Idle> help /vis/sceneHandler/create

The list is, for example, displayed as follows:

.....
Candidates : DAWNFILE OGL
.....

For additional options, see the Control...UICommands section of this user guide.

8.4.3.  Create an empty scene: /vis/scene/create command

Command "/vis/scene/create" creates an empty scene, which corresponds to Step 2.

Command: /vis/scene/create [scene_name]

  • Argument

    A name for this scene. Created for you if you don't specify one.

8.4.4.  Visualization of a physical volume: /vis/drawVolume command

Command "/vis/drawVolume" adds a physical volume to the scene. It also does some of the other steps, if you haven't done them explicitly. It takes care of steps 2, 3, 4 and 6. Command "/vis/viewer/flush" should follow in order to do the final Step 7.

Commands:

/vis/drawVolume [physical-volume-name]
.....
Idle> /vis/viewer/flush

  • Argument

    A physical-volume name. The default value is "world", which is omittable.

  • Action

    Creates a scene consisting of the given physical volume and asks the current viewer to draw it. The scene becomes current. Command "/vis/viewer/flush" should follow this command in order to declare end of visualization.

  • Example: Visualization of the whole world with coordinate axes

        Idle> /vis/drawVolume
        Idle> /vis/scene/add/axes 0 0 0 500 mm
        Idle> /vis/viewer/flush
        

8.4.5.  Visualization of a logical volume: /vis/specify command

Command "/vis/specify" visualizes a logical volume. If allows you to control how much details is shown and whether to show booleans, voxels and readout geometries. It also does some of the other steps, if you haven't done them explicitly. It takes care of steps 2, 3, 4 and 6. Command "/vis/viewer/flush" should follow the command in order to do the final Step 7.

Command: /vis/specify [logical-volume-name][depth-of-descent] [booleans-flag] [voxels-flag] [readout-flag]

  • Argument

    A logical-volume name.

  • Action

    Creates a scene consisting of the given logical volume and asks the current viewer to draw it. The scene becomes current.

  • Example (visualization of a selected logical volume with coordinate axes)

        Idle> /vis/specify Absorber
        Idle> /vis/scene/add/axes 0 0 0 500 mm
        Idle> /vis/scene/add/text 0 0 0 mm 40 -100 -200 LogVol:Absorber
        Idle> /vis/viewer/flush
        

For more options, see the Control...UICommands section of this user guide.

8.4.6.  Visualization of trajectories: /vis/scene/add/trajectories command

Command "/vis/scene/add/trajectories [smooth] [rich]" adds trajectories to the current scene. The optional parameters "smooth" and/or "rich" (you may specify either, both or neither) invoke, if "smooth" is specified, the storing and displaying of extra points on curved trajectories and, if "rich" is specified, the storing, for possible subsequent selection and display, of additional information, such as volume names, creator process, energy deposited, global time. Be aware, of course, that this imposes computational and memory overheads. Note that this automatically issues the appropriate "/tracking/storeTrajectory" command so that trajectories are stored (by default they are not). The visualization is performed with the command "/run/beamOn" unless you have non-default values for /vis/scene/endOfEventAction or /vis/scene/endOfRunAction (described below).

Command: /vis/scene/add/trajectories [smooth] [rich]

  • Action

    The command adds trajectories to the current scene. Trajectories are drawn at end of event when the scene in which they are added is current.

  • Example: Visualization of trajectories

        Idle> /vis/scene/add/trajectories
        Idle> /run/beamOn 10
        

  • Additional note 1

    See the section Section 8.7.3 Enhanced Trajectory Drawing for details on how to control how trajectories are color-coded.

  • Additional note 2

    Events may be kept and reviewed at end of run with

        Idle> /vis/reviewKeptEvents
        

    Keep all events with

        Idle> /vis/scene/endOfEventAction accumulate [maxNumber]
        

    (see Section 8.4.12)

    or keep some chosen subset with

        G4EventManager::GetEventManager()->KeepTheCurrentEvent();
        

    as described in Example 6.8.

    To suppress drawing during a run

        Idle> /vis/disable
        Idle> /run/beamOn 10000
        

    then at end of run

        Idle> /vis/enable
        Idle> /vis/reviewKeptEvents
        

For more options, see the Control...UICommands section of this user guide.

8.4.7.  Visualization of hits: /vis/scene/add/hits command

Command "/vis/scene/add/hits" adds hits to the current scene, assuming that you have a hit class and that the hits have visualization information. The visualization is performed with the command "/run/beamOn" unless you have non-default values for /vis/scene/endOfEventAction or /vis/scene/endOfRunAction (described above).

8.4.8.  Visualization of Scored Data

Scored data can be visualized using the commands "/score/drawProjection" and "/score/drawColumn". For details, see examples/extended/runAndEvent/RE03.

8.4.9.  HepRep Attributes for Hits

The HepRep file formats, HepRepFile and HepRepXML, attach various attributes to hits such that you can view these attributes, label trajectories by these attributes or make visibility cuts based on these attributes. Examples of adding HepRep attributes to hit classes can be found in examples /extended/analysis/A01 and /extended/runAndEvent/RE01.

For example, in example RE01's class RE01CalorimeterHit.cc, available attributes will be:

  • Hit Type
  • Track ID
  • Z Cell ID
  • Phi Cell ID
  • Energy Deposited
  • Energy Deposited by Track
  • Position
  • Logical Volume

You can add additional attributes of your choosing by modifying the relevant part of the hit class (look for the methods GetAttDefs and CreateAttValues).

8.4.10.  Basic camera workings: /vis/viewer/ commands

Commands in the command directory "/vis/viewer/" set camera parameters and drawing style of the current viewer, which corresponds to Step 5. Note that the camera parameters and the drawing style should be set separately for each viewer. They can be initialized to the default values with command "/vis/viewer/reset". Some visualization systems, such as the VRML and HepRep browsers also allow camera control from the standalone graphics application.

Just a few of the camera commands are described here. For more commands, see the Control...UICommands section of this user guide.

The view is defined by a target point (initially at the centre of the extent of all objects in the scene), an up-vector and a viewpoint direction - see Figure 8.1. By default, the up-Vector is parallel to the y-axis and the viewpoint direction is parallel to the z-axis, so the the view shows the x-axis to the right and the y-axis upwards - a projection on to the canonical x-y plane - see Figure 8.2.

The target point can be changed with a /vis/viewer/set command or with the /vis/viewer/pan commands. The up-vector and the viewpoint direction can also be changed with /vis/viewer/set commands. Care must be taken to avoid having the two vectors parallel, for in that case the view is undefined.

Up-vector and viewpoint direction

Figure 8.1.  Up-vector and viewpoint direction


The default view

Figure 8.2.  The default view


Command: /vis/viewer/set/viewpointThetaPhi [theta] [phi] [deg|rad]

  • Arguments

    Arguments "theta" and "phi" are polar and azimuthal camera angles, respectively. The default unit is "degree".

  • Action

    Set a view point in direction of (theta, phi).

  • Example: Set the viewpoint in direction of (70 deg, 20 deg) /

        Idle> /vis/viewer/set/viewpointThetaPhi 70 20
        

  • Additional notes

    Camera parameters should be set for each viewer. They are initialized with command "/vis/viewer/reset". Alternatively, they can be copied from another viewer with the command "/vis/viewer/copyViewFrom viewer-0", for example.

Command: /vis/viewer/zoom [scale_factor]

  • Argument

    The scale factor. The command multiplies magnification of the view by this factor.

  • Action

    Zoom up/down of view.

  • Example: Zoom up by factor 1.5

        Idle> /vis/viewer/zoom 1.5
        

  • Additional notes

    A similar pair of commands, scale and scaleTo allow non-uniform scaling (i.e., zoom differently along different axes). For details of this and lots of other commands, see the Control...UICommands section of this user guide.

    Some viewers have limits to how large the zoom factor can be. This problem can be circumnavigated to some degree by using zoom and scale together. If

        Idle> /vis/viewer/zoomTo 1e10
        

    does not work, please try

        Idle> /vis/viewer/scaleTo 1e5 1e5 1e5
        Idle> /vis/viewer/zoomTo 1e5
        

    Of course, with such high zoom factors, you might want to know whither you are zooming. Use "/vis/viewer/set/targetPoint"

    Camera parameters should be set for each viewer. They are initialized with command "/vis/viewer/reset". Alternatively, they can be copied from another viewer with the command "/vis/viewer/copyViewFrom viewer-0", for example.

Command: /vis/viewer/set/style [style_name]

  • Arguments

    Candidate values of the argument are "wireframe" and "surface". ("w" and "s" also work.)

  • Action

    Set a drawing style to wireframe or surface.

  • Example: Set the drawing style to "surface"

        Idle> /vis/viewer/set/style surface
        

  • Additional notes

    The style of some geometry components may have been forced one way or the other through calls in compiled code. The set/style command will NOT override such force styles.

    Drawing style should be set for each viewer. The drawing style is initialized with command "/vis/viewer/reset". Alternatively, it can be copied from another viewer with the command "/vis/viewer/set/all viewer-0", for example.



8.4.11.  Declare the end of visualization for flushing: /vis/viewer/flush command

Command: /vis/viewer/flush

  • Action

    Declare the end of visualization for flushing.

  • Additional notes

    Command "/vis/viewer/flush" should follow "/vis/drawVolume", "/vis/specify", etc in order to complete visualization. It corresponds to Step 7.

    The flush is done automatically after every /run/beamOn command unless you have non-default values for /vis/scene/endOfEventAction or /vis/scene/endOfRunAction (described above).

8.4.12.  End of Event Action and End of Run Action: /vis/viewer/endOfEventAction and /vis/viewer/endOfRunAction commands

By default, a separate picture is created for each event. You can change this behavior to accumulate multiple events, or even multiple runs, in a single picture.

Command: /vis/scene/endOfEventAction [refresh|accumulate]

  • Action

    Control how often the picture should be cleared. refresh means each event will be written to a new picture. accumulate means events will be accumulated into a single picture. Picture will be flushed at end of run, unless you have also set /vis/scene/endOfRunAction accumulate

  • Additional note

    You may instead choose to use update commands from your BeginOfRunAction or EndOfEventAction, as in early examples, but now the vis manager ia able to do most of what most users require through the above commands.

Command: /vis/scene/endOfRunAction [refresh|accumulate]

  • Action

    Control how often the picture should be cleared. refresh means each run will be written to a new picture. accumulate means runs will be accumulated into a single picture. To start a new picture, you must explicitly issue /vis/viewer/refresh, /vis/viewer/update or /vis/viewer/flush

8.4.13.  HepRep Attributes for Trajectories

The HepRep file formats, HepRepFile and HepRepXML, attach various attributes to trajectories such that you can view these attributes, label trajectories by these attributes or make visibility cuts based on these attributes. If you use the default Geant4 trajectory class from /tracking/src/G4Trajectory.cc (this is what you get with the plain /vis/scene/add/trajectories command), available attributes will be:

  • Track ID
  • Parent ID
  • Particle Name
  • Charge
  • PDG Encoding
  • Momentum 3-Vector
  • Momentum magnitude
  • Number of points

Using /vis/scene/add/trajectories rich will get you additional attributes. You may also add additional attributes of your choosing by modifying the relevant part of G4Trajectory (look for the methods GetAttDefs and CreateAttValues). If you are using your own trajectory class, you may want to consider copying these methods from G4Trajectory.

8.4.14.  How to save a visualized views to PostScript files

Most of the visualization drivers offer ways to save visualized views to PostScript files (or Encapsulated PostScript (EPS) files) by themselves.

  • DAWNFILE

    The DAWNFILE driver, which co-works with Fukui Renderer DAWN, generates "vectorized" PostScript data with "analytical hidden-line/surface removal", and so it is well suited for technical high-quality outputs for presentation, documentation, and debugging geometry. In the default setting of the DAWNFILE drivers, EPS files named "g4_00.eps, g4_01.eps, g4_02.eps,..." are automatically generated in the current directory each time when visualization is performed, and then a PostScript viewer "gv"is automatically invoked to visualize the generated EPS files.

    For large data sets, it may take time to generate the vectorized PostScript data. In such a case, visualize the 3D scene with a faster visualization driver beforehand for previewing, and then use the DAWNFILE drivers. For example, the following visualizes the whole detector with the OpenGL-Xlib driver (immediate mode) first, and then with the DAWNFILE driver to generate an EPS file g4_XX.eps to save the visualized view:

    # Invoke the OpenGL visualization driver in its immediate mode
    /vis/open OGLIX 
    
    # Camera setting
    /vis/viewer/set/viewpointThetaPhi 20 20
    
    # Camera setting
    /vis/drawVolume 
    /vis/viewer/flush
    
    # Invoke the DAWNFILE visualization driver 
    /vis/open DAWNFILE
    
    # Camera setting
    /vis/viewer/set/viewpointThetaPhi 20 20
    
    # Camera setting
    /vis/drawVolume 
    /vis/viewer/flush
    

    This is a good example to show that the visualization drivers are complementary to each other.

  • OpenInventor

    In the OpenInventor drivers, you can simply click the "Print" button on their GUI to generate a PostScript file as a hard copy of a visualized view.

  • OpenGL

    The OpenGL drivers can also generate PostScript files, either from a pull-down menu (Motif and Qt drivers) or with /vis/ogl/printEPS. It can generate either vector or bitmap PostScript data with /vis/ogl/set/printMode ("vectored" or "pixmap"). You can change the filename by /vis/ogl/set/printMode And the print size by /vis/ogl/set/printSize In generating vectorized PostScript data, hidden-surface removal is performed based on the painter's algorithm after dividing facets of shapes into small sub-triangles.

    Note that a fundamental limitation of the gl2ps library used for this PostScript printing causes the /vis/viewer/set/hiddenMarker command to be ignored. Trajectories will always be fully drawn in the printEPS output even when the hiddenMarker hidden line removal option has been set to hide these trajectories in the corresponding OpenGL view.

    The /vis/ogl/set/printSize command can be used to print EPS files even larger than the current screen resolution. This can allow creation of very large images, suitable for creation of posters, etc. The only size limitation is the graphics card's viewport dimension: GL_MAX_VIEWPORT_DIMS

    # Invoke the OpenGL visualization driver in its stored mode
    /vis/open OGLSX 
    
    # Camera setting
    /vis/viewer/set/viewpointThetaPhi 20 20
    
    # Camera setting
    /vis/drawVolume 
    /vis/viewer/flush
    
    # set print mode to vectored
    /vis/ogl/set/printMode vectored
    
    # set print size larger than screen
    /vis/ogl/set/printSize 2000 2000
    
    # print
    /vis/ogl/printEPS
    
    

  • HepRep

    The HepRApp HepRep Browser and WIRED4 JAS Plug-In can generate a wide variety of bitmap and vector output formats including PostScript and PDF.

8.4.15.  Culling

"Culling" means to skip visualizing parts of a 3D scene. Culling is useful for avoiding complexity of visualized views, keeping transparent features of the 3D scene, and for quick visualization.

Geant4 Visualization supports the following 3 kinds of culling:

  • Culling of invisible physical volumes
  • Culling of low density physical volumes.
  • Culling of covered physical volumes by others

In order that one or all types of the above culling are on, i.e., activated, the global culling flag should also be on.

Table 8.3 summarizes the default culling policies.

Culling Type Default Value
global ON
invisible ON
low density OFF
covered daughter OFF

Table 8.3.  The default culling policies.



The default threshold density of the low-density culling is 0.01 g/cm3.

The default culling policies can be modified with the following visualization commands. (Below the argument flag takes a value of true or false.)

     # global
     /vis/viewer/set/culling  global  flag

     # invisible
     /vis/viewer/set/culling  invisible  flag

     # low density
     #   "value" is a proper value of a treshold density
     #   "unit" is either g/cm3, mg/cm3 or kg/m3
     /vis/viewer/set/culling  density  flag  value  unit 

     # covered daughter
     /vis/viewer/set/culling  coveredDaughters  flag     density

The HepRepFile graphic system will, by default, include culled objects in the file so that they can still be made visible later from controls in the HepRep browser. If this behavior would cause files to be too large, you can instead choose to have culled objects be omitted from the HepRep file. See details in the HepRepFile Driver section of this user guide.

8.4.16.  Cut view

Sectioning

"Sectioning" means to make a thin slice of a 3D scene around a given plane. At present, this function is supported by the OpenGL drivers. The sectioning is realized by setting a sectioning plane before performing visualization. The sectioning plane can be set by the command,

     /vis/viewer/set/sectionPlane on x y z units nx ny nz

where the vector (x,y,z) defines a point on the sectioning plane, and the vector (nx,ny,nz) defines the normal vector of the sectioning plane. For example, the following sets a sectioning plane to a yz plane at x = 2 cm:

     Idle> /vis/viewer/set/sectionPlane  on  2.0  0.0  0.0  cm  1.0  0.0  0.0

Cutting away

"Cutting away" means to remove a half space, defined with a plane, from a 3D scene.

  • Cutting away is supported by the DAWNFILE driver "off-line". Do the following:

    • Perform visualization with the DAWNFILE driver to generate a file g4.prim, describing the whole 3D scene.

    • Make the application "DAWNCUT" read the generated file to make a view of cutting away.

    See the following WWW page for details: http://geant4.kek.jp/GEANT4/vis/DAWN/About_DAWNCUT.html

  • Alternatively, add up to three cutaway planes:

         /vis/viewer/addCutawayPlane 0 0 0 m 1 0 0
         /vis/viewer/addCutawayPlane 0 0 0 m 0 1 0
         ...
        

    and, for more that one plane, you can change the mode to

    • (a) "add" or, equivalently, "union" (default) or
    • (b) "multiply" or, equivalently, "intersection":

         /vis/viewer/set/cutawayMode multiply
        

    To de-activate:

         /vis/viewer/clearCutawayPlanes
        

    OpenGL supports this feature.

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