Walkthrough on creation of 3d scenes

This walkthrough shows how to create graphic depictions of tomogram contents. Those include:

• Slices of tomograms.
• Proteins located in the tomogram, with the orientations provided during the alignment.
• Geometrical objects (as membranes represented by triangulations).

Goal of the tutorial. An antialiasing filter has been used.

The data set

This walkthrough works with the data set from the advanced starters guide. The goal is to depict:

• One slice of the tomogram in 3D.
  This requires a tomogram file.
• The viruses placed an oriented along the directions found during a previous computed average.
  This requires a template represe.
• A sketch of the membrane
  This requires a model object.

From the Dynamo web

The tomogram can get fetched through:

wget  https://wiki.dynamo.biozentrum.unibas.ch/w/doc/data/fhv/crop.rec 

in a linux shell, or through:

curl -O  https://wiki.dynamo.biozentrum.unibas.ch/w/doc/data/fhv/crop.rec 

under MacOS.

The table, template and membrane model can be fetched similarly with names

https://wiki.dynamo.biozentrum.unibas.ch/w/doc/data/fhv/alignmentLocalRefinement.tbl
https://wiki.dynamo.biozentrum.unibas.ch/w/doc/data/fhv/averagedLocalRefinement.em
https://wiki.dynamo.biozentrum.unibas.ch/w/doc/data/fhv/membraneModel.omd

From your previous work

Assuming you have done the tutorial on the FHV data set, you can use the elements that you have already computed. Just extract them from the best project that you completed. Do not use a subboxing project: we want to get a template for the full crown. Examples below are given assuming that your best project was named localized, substitute if not.

Table

Recover the last computed refined table in the data base of your project

ddb localized:rt -r t

and write it to a file

dwrite(t,'alignmentLocalRefinement.tbl')

Template

Fetch the last computed average

ddb localizedFullAngle:rt -r a

and write it into disk

 dwrite(t,'averagedLocalRefinement.tbl'); 

Membrane model

If you created manually a membrane model, it should be inside your catalogue with the name mySurface (or any other you put). You can check inside the catalogue fhv:

dcmodels fhv -nc mySurf

Here -nc mySurf will look for models with the string "mySurf" in the name. You should get a reply as:

Volume 1. Matching models: 1 (total: 1) /Users/casdanie/dynamo/examples/fhvParis/fhv/tomograms/volume_1/models/mySurface.omd

So you can read the model into a new variable (arbitrarily called m)

m = drread('Users/casdanie/dynamo/examples/fhvParis/fhv/tomograms/volume_1/models/mySurface.omd');

and write it to disk

dwrite(m,'membraneModel.omd');

Depicting a slice of a tomogram

The slice object

s = dpktomo.volume.slices.Slice(); 

Here s is just an object that will read data from a tomogram file to be defined, along with geometrical parameters as center, eulers (orientation), l, (sidelength)...

s.source = 'crop.rec';
s.center = 'center';

Here, we set the center of the slice. We can pass a [x,y,z] triplet (like [256,200,100], or just use the code 'center' to put the center of the slice in the center of the tomogram. Now, we indicate the horizontal and vertical lengths of the slice (in pixels):

s.l = [1000,1000];

The actual extent of the slice will get cut if the l that we use is bigger than the size of the tomogram.

The orientation of the slice can be computed through a combination of euler angles [tdrort, tilt, narot], or simply with strings 'x', 'y' and 'z' for orthogonal directions. s.eulers = 'z';

Now, we actually compute the slice;

s.fetchData();

This will not create any output in the screen. fetchData will just operate the action of visiting the file crop.rec and extracting a numeric matrix that represents the gray intensities of the slice with the indicated parameters. The matrix will be stored inside the s object (as the 'data' property) and will be accessed by the depicting operations to be executed later.

The slice depictor object

We first create a figure with and empty axis f = figure; haxis = gca();hold on;

Empty matlab figure with an empty axis.

Here, f are handles that will be used later to direct the graphical output to our figure.

Now, we initialize a depiction object associated with the slice s sz = dpktomo.volume.slices.SliceGraphic(s); Note that no graphical output has been created yet. We first inform the object sz in which axis it is to be created.

sz.axis.h = haxis;

and then create the slice in the available axis.

sz.create();

If the figure is below other windows in your system you can rise it through

shg; 

or

figure(f);

We can change the angle of view with the rotation icon or programmatically:

view([-38,60]);

View of the slice with the viewing perspective ([-38,60]).

Placement of templates

Here we will place copies of an FHV crown in the positions and orientations given by a table. Here, the density map representing the template needs first to be converted into an isosurface, which will be represented by a triangulation.

Creating a mask

We first want to crop the available average inside a mask, to get rid of the membrane surrounding the crown. For this we first show the template inside mapview

dmapview averagedLocalRefinement.em

mapview on template.

We can apply a 'c12' symmetrization on the template to get better graphical depiction.

Rotational symmetrization of a template.

Now, we can select the area of interest by moving to the central section

Central section in the xz plane.

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Checking the isolevel in Chimera

You can check the appropriate isolevel using Chimera UCSF, assuming it is activated in your session.

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