Visualize and Plot the Output


The simulations and visualizations in this tutorial were generated using Blender 2.70a and CellBlender 1.0. It may or may not work with other versions.

At the end of the last section, we ran the MCell simulation from within CellBlender. This generated visualization and reaction data (i.e. molecule counts), which we will now examine using CellBlender and some plotting software.

Visualize the Molecules

If you closed the intro.blend file that we generated in getting_started, reopen it now (blender intro.blend). Then click the Scene button in the Properties Editor. Expand the Visualize Simulation Results panel and click the Read Viz Data button.


You should now see a number of molecules populating the surface of the Cube.

Let's change the Cube to a wireframe view so we can see inside of it. First, be sure that the cube is selected (orange outline). Then click the Object button on the Properties Editor.


Under the Display panel, change Maximum Draw Type to Wire.


Drag the green bar on the Timeline Editor back and forth to scrub through the simulation. You can see the molecules diffusing in and on surface of the cube, and new molecules being created outside the cube.

Customize Molecule Glyphs

By default, every molecule just shows up as a sphere. This might be fine for volume molecules, but you might want to be able to tell the orientation of your surface molecules, which we can do by using an asymmetrical glyph.

Expand molecules in the Outliner by clicking the small + sign beside it. This expands to reveal mol_surf1, mol_vol1, and mol_vol2. These correspond to the molecules we created in our simulation: surf1, vol1, and vol2.


If you click the plus beside each of these, you will see mol_surf1_shape, mol_vol1_shape, and mol_vol2_shape. These are the actual glyph objects that get mapped onto the molecule locations. Select mol_surf1_shape in the Outliner.


The molecules are probably hard to see, so let's fix this problem. In the 3D View Editor, hit s, 3, and Enter to increase the size of mol_surf1_shape three times. Repeat this process for mol_vol1_shape and mol_vol2_shape. Everything should be a little easier to see now. Regardless, you may want to zoom in to get an even better view of them (roll the middle mouse wheel up in the 3D View Editor).


Now let's get back to updating the glyph for surf1. Reselect, mol_surf1_shape in the Properties Editor. Then click the Material button and navigate down to Molecule Shape.


The shape should be set to Cone in the Molecule Shape drop down box. Click Set Molecule Shape to apply the selection.


All of the surf1 molecule glyphs should now be changed to cones.


Graph the Reaction Data inside Blender

CellBlender allows users to plot reaction data (molecule and reaction counts) from within Blender itself. This requires the installation of optional external applications (currently matplotlib or xmgrace).


CellBlender will attempt to autodetect the presence of these by seeing if they are in your PATH (and that the required modules are accessible in the

You can see which plotting applications are currently installed by checking the Reaction Output Settings panel shown here:


In the lower half of that panel you will find buttons for each of the plotting applications that CellBlender has found (see "Installing Plotting Plug-Ins" for information on installing new plug-ins). In the panel above, it shows three plotting options:

  • matplotlib Plotter
  • XmGrace Plotter
  • Simple Plotter (also uses matplotlib)

Each of those will attempt to plot all of your reaction output data files according to the specification options set above the buttons. In this example, the plot layout setting is "One Page, Multiple Plots" so the data files will all be plotted on one single page, but each data file will be in its own plot within that page. Because the Combine Seeds option is checked, all files of the same name but with different seeds will be combined on the same plot. Since Molecule Colors is also selected, the color of the line will match the color of the molecule's glyph.

Advanced Plotting


The following sections describe advanced features that are not intended for the average user.

Installing Plotting Plug-Ins

CellBlender supports a variety of plotting plug-ins that may be installed in the "data_plotters" folder under the cellblender addon folder (typically something like: ~/.config/blender/2.70/scripts/addons/cellblender/data_plotters). Each plotting plug-in will have its own folder in that directory, and within that folder must (at least) be a file named As an example, the xmgrace plug-in will be found at ~/.config/blender/2.70/scripts/addons/cellblender/data_plotters/xmgrace. There may be other files required in that folder. For example, the Java Plotter requires the file PlotData.jar to be there, and the matplotlib plotter requires the files and The number and purposes of these additional files depends completely on the plotting plug-in.

Installing a new plotting plug-in only requires the creation of a new directory in the data_plotters directory (the name can be whatever you feel is appropriate), and the installation of the associated files (which must include an file.

Here's an example of a simple plotting plug-in for xmgrace:

import os
import subprocess

def find_in_path(program_name):
    for path in os.environ.get('PATH','').split(os.pathsep):
        full_name = os.path.join(path,program_name)
        if os.path.exists(full_name) and not os.path.isdir(full_name):
            return full_name
    return None

def get_name():
    return ( "XmGrace Plotter" )

def requirements_met():
    path = find_in_path ( "xmgrace" )
    if path == None:
        print ( "Required program \"xmgrace\" was not found" )
        return False
        return True

def plot ( data_path, plot_spec ):
    program_path = os.path.dirname(__file__)

    # XmGrace expects plain file names so translate:

    plot_cmd = find_in_path ( "xmgrace" )

    for plot_param in plot_spec.split():
        if plot_param[0:2] == "f=":
            plot_cmd = plot_cmd + " " + plot_param[2:]

    pid = subprocess.Popen ( plot_cmd.split(), cwd=data_path )


This plotting api is still being developed and changes are expected!

Writing Plotting Plug-Ins

CellBlender's plotting plug-in API is still very immature, so drastic changes may be anticipated. But for those who need to write their own plotting plug-in, the current specification is as follows...

Each plotting plug-in must have an file containing the following functions:

  • get_name()
  • requirements_met()
  • plot ( data_path, plot_spec )

These are described in separate sections below.


The get_name() function simply returns the name of this plug-in in the form of a normal python string. This is used for the user interface.


The requirements_met() function is called to determine if the operating environment meets the requirements for this plug-in to work. For example, if the plug-in is written in Java, then the requirements_met function should check to see that a suitable Java Virtual Machine is installed. This function returns True if the requirements are met, and false otherwise.

plot ( data_path, plot_spec )

The plot() function actually performs the plot. The plot function takes two parameters:

  • data_path - a path to where the data files exist (added to each file)
  • plot_spec - a list of files and modifiers that describe the plotting

The data_path is fairly self-explanatory, but the plot_spec requires a little bit of explanation.

The fundamental plot specification is just a list of file names immediately prefixed with "f=" and separated by spaces:

f=mol1v1.dat f=mol1v2.dat f=mol1s1.dat f=mol2s1.dat

Every plotting plug-in should recognize the "f=" prefix as specifying the name of a file where the file itself contains two columns of numbers (time and count) in ASCII text format. As a minimum, the plug-in should be able to plot all such files in a single plot.

At this point, all additional parameters are optional ... but certainly useful!

Among the optional parameters are the separators "page" and "plot". These are inserted between file names to produce either a new page or a new plot. For example, the previous specification could plot the volume and surface molecules in two separate plots within the same page using this command:

f=mol1v1.dat f=mol1v2.dat plot f=mol1s1.dat f=mol2s1.dat

Alternatively, the the following command will put each of those plots on their own pages:

f=mol1v1.dat f=mol1v2.dat page f=mol1s1.dat f=mol2s1.dat

This command creates two pages and creates 2 plots on each page:

f=mol1v1.dat plot f=mol1v2.dat page f=mol1s1.dat plot f=mol2s1.dat

Finally, here is the current plotting plug-in API (SUBJECT TO CHANGE)

  • defs=filename ... Loads default parameters from a python file
  • page ... Starts a new page (figure in matplotlib)
  • plot ... Starts a new plot (subplot in matplotlib)
  • color=#rrggbb ... Selects a color via Red,Green,Blue values
  • color=color_name ... Selects a color via standard color names
  • title=title_string ... Sets the title for each plot
  • pagetitle=string ... Sets the title for each page
  • xlabel=label_string ... Sets the label for the x axis
  • ylabel=label_string ... Sets the label for the y axis
  • legend=code ... Adds a legend with code = 0..10 (-1=none)
  • n=name ... Name used to over-ride file name in legend
  • f=filename ... Plots the file with current settings