DMelt:Plots/VisAd

Table of contents

VisAd

DataMelt includes VisAd, which was destined by programmers at the University of Wisconsin Space Science and Engineering Center (SSEC). We reproduce its guide in VisAd guide section

The Java API is given by  visad package.

VisAd tutorial

Here is a short tutorial how to visualize numerical information using interactive canvas called  jhplot.HVisAd. We will show step-by step example, starting from elementary operation, such as opening the canvas and creating a 3D scene.

from jhplot import *
from java.awt import *
c1 = HVisAd("VisAd",600,600)  # make 600x600 canvas
display = c1.getDisplay()     # get display
ren=c1.getRender()            # get display render
ren.setBoxOn(True)            # draw a box
ren.setBackgroundColor(Color.white)  # make it white
c1.visible()                  # show it

Next, we will try to manipulate with the box. For example, we can zooming (or zoom out), move it and rotate:

from jhplot import *
c1 = HVisAd("VisAd",600,600)
ren=c1.getRender()
ren.setBoxOn(True)
c1.setScaling(0.8)
c1.setRotation(0,20,0)         # rotation around Y in 20 deg 
c1.setTranslation(0.1,0.0,0.0) # shift in X by 10%  
c1.visible()                   # show it

You can use full Java API of VisAd to archive scaling and rotations using the "ProjectionControl" method:

from jhplot import *
from java.awt import *
c1 = HVisAd("test",600,500)
display = c1.getDisplay()
ren=c1.getRender()
proj = ren.getDisplay().getProjectionControl();
mouseBehavior = ren.getMouseBehavior()
tstart = proj.getMatrix()
scale=0.5
t1 = mouseBehavior.make_matrix(0.0, 0.0, 0.0, scale, 0.0, 0.0, 0.0)
t1 = mouseBehavior.multiply_matrix(t1, tstart)
proj.setMatrix(t1)
ren.setBoxOn( True )
c1.visible() # show canvas

So far we had just a box. Now we can draw axises. Here is an example how to set axis, define their ranges

from jhplot import *
c1 = HVisAd("VisAd")
display=c1.getDisplay()
cont=display.getGraphicsModeControl()
cont.setSceneAntialiasingEnable(True)
cont.setLineWidth(1)
ren=c1.getRender(); ren.setBoxOn(True) # draw a box 
c1.setAxes("X",0,10,"Y",0,10,"Z",0,10)
c1.visible() # show canvas

The method setAxes() takes the name of the axis, min and max value for X,Y,Z axis. Here is a more refined example that shows how to make custom frame with axis:

from jhplot import *
from java.awt import Font
from visad import Display,ScalarMap,RealType

c1 = HVisAd("VisAd",600,600)
display=c1.getDisplay()
cont=display.getGraphicsModeControl()
cont.setSceneAntialiasingEnable(True)
cont.setLineWidth(2)
ren=c1.getRender(); ren.setBoxOn(True) # draw a box 

x=RealType("x"); y=RealType("y");  z=RealType("z") # make  X,Y,Z axis
rX = ScalarMap(x,Display.XAxis)
rY = ScalarMap(y,Display.YAxis)
rZ = ScalarMap(z,Display.ZAxis)

rX.setScalarName("X axis")
rY.setScalarName("Y axis")
rZ.setScalarName("Z axis")

col=[0.1, 0.1, 0.1] # change color  
rX.setScaleColor(col)
rY.setScaleColor(col)
rZ.setScaleColor(col)

# set min and max ranges
rX.setRange(0,10)
rY.setRange(0,20)
rZ.setRange(0,100)

axisX=rX.getAxisScale() # this is visad.AxisScale object
axisX.setFont(Font("Arial", Font.BOLD, 16))
axisX.setLabelSize(16)
axisX.setGridLinesVisible(True)

# attach to the box? 
# axisX.setSnapToBox(True) 
# axisX.setLabelBothSides(True)

display.addMap( rX )
display.addMap( rY )
display.addMap( rZ )

c1.visible() # show canvas

Using full VisAd Java api

Here is a Jython macro which shows ho to visualize 2D data calling Java classes directly:

from visad import SI,Integer1DSet,RealType
from visad import FunctionType, FieldImpl, ScalarMap, Display
from visad import Display,FlatField,DataReferenceImpl
from visad.java2d import DisplayImplJ2D

time = RealType("time",SI.second)
height = RealType("height",SI.meter)

# Create a FunctionType, that is the class which represents our function
#  This is the MathType ( time -> height )
# Use FunctionType(MathType domain, MathType range)
func_time_height = FunctionType(time, height)


# Those are our actual height values
# Note the dimensions of the array:
# float[ number_of_range_components ][ number_of_range_samples]
h_vals =[[0.0, 33.75, 45.0, 33.75, 0.0]] 


# Create the time_set, with 5 integer values, ranging from 0 to 4.
# That means, that there should be 5 values for height.
# Use Integer1DSet(MathType type, int length)
time_set = Integer1DSet(time, 5);

vals_ff = FlatField( func_time_height, time_set);

# and put the height values above in it
vals_ff.setSamples( h_vals );

# create canvas
display = DisplayImplJ2D("display1");

# Create the ScalarMaps: quantity time is to be displayed along x-axis
# and height along y-axis
# Use ScalarMap(ScalarType scalar, DisplayRealType display_scalar)
timeMap = ScalarMap( time, Display.XAxis );
heightMap = ScalarMap( height, Display.YAxis );


# Add maps to display
display.addMap( timeMap );
display.addMap( heightMap );


#  Create a data reference and set the FlatField as our data
data_ref = DataReferenceImpl("data_ref");
data_ref.setData( vals_ff );


# Add reference to display
display.addReference( data_ref );

from javax.swing import JFrame
# Create application window, put display into it
jf=JFrame("VisAD application");
jf.getContentPane().add(display.getComponent())

# Set window size and make it visible
jf.setSize(600, 400);
jf.setVisible(True);