'vlrender' is a volume rendering program. The creation of 3d-renderings becomes straightforward since the appearance of the rendered volumes can be completely controlled within a graphical user interface (gui) in real-time. Clipping objects like planes or boxes can be placed freely to 'open up' parts of the volume and to show whats inside.
Anatomical and zmap data can be rendered in a single step to images of arbitrary size (resolution).
Pre-rendering for standard anatomical MRI datasets is no longer required.
vlrender -in mrxxx_t1_or.v
or in combination with a zmap:
vlrender -in norm_brain.v -zmap cgtbsGV1T.v
The 'vlrender' main window will appear showing the rendered volume inside.
If you move the mouse-cursor over the rendered volume, it will change its shape to
a little hand. By pressing and keeping pressed one of the three mouse-buttons,
the volume can be rotated (left button), translated (middle button) and zoomed
(right button) while moving the mouse.
The speed of the rendering and thus the fluency of the display and vlrender-gui
depends strongly on the performance of the processor. 'vlrender'
can be adapted in rendering speed and quality by changing the slider at the
bottom of the main window. Moving the slider to the left will decrease the
render quality and thus increase rendering speed. Moving the slider to the right
will behave vice versa.
Note: Saving an image to a file is always performed in
highest possible quality and will not be affected by this setting. See below.)
The main functions of 'vlrender' can be controlled by selecting the appropriate
item from menu or toolbar on the top of the main window or just by pressing
the associated key on the keyboard. Most of the functions are self-explanatory.
See the 'Online Help'-Entry in the Help-Menu of 'vlrender'.
To e.g. enable the clipping box, select the 'Clip-Box' entry from the 'Options'-Menu, click on
the box icon at the toolbar or simply type 'B' on the keyboard.
The clipping box and an additional dialog to control clipping properties are displayed. The clipping box
can be moved in x- and z-direction by keeping pressed the middle mouse-button
and in y-direction by keeping pressed the right mouse-button while moving the mouse.
The behaviour and use of the clipping plane is similar to that of the clipping box described above,
except that it can only be moved along the direction orthogonal to its orientation using the
middle mouse-button.
Keep in mind: Either the clipping object or the volume is active for modification. To toggle the
active object, simply press the space bar at the keyboard or select the icon showing a lock at the
toolbar. The type of the currently active object is always shown at the lower right corner of the main window.
To disable the current clipping object, click at the appropriate menu- or toolbar-item again.
Zmap are volumes, like the anatomy data, but sometime it is desirable to have the
functional data only on the anatomy border. This is possible using the projection button
or simply press 'T'.
Be aware the projection may take some time. It also projects only the zmap-values inside the zmap thresholds. If you change these thresholds, you have to recalculate the projection. The greater the thresholds the longer the duration of the calculation.
After the calculation is finished the projection will rendered instead of the zmap. By clicking on the projection button, you can change the zmap render mode. If the thresholds of the zmap stay constant, no recalculation is needed and a cached projection is used, so after the initial calculation the duaration of toggling the zmap mode depends on the rendering time.
If you have a zmap, which marks some regions with an index, e.g. files created with vshowpts it is possible to colorize these regions with a sprecific color. Therefor you need an additional file called the colormap.
A colormap file is a simple text file. The zmap value, called index and the color is written in one row, containing for columns with integer numbers.
The first number is the index, the second the red color value, the third the green value and the fourth is the value for the blue value of the RGB encoded color. The numbers may be seperated by one tab or space.
The colortable file format supports comments, which are lines beginning with # or %. Comments have to be on a seperated line. Empty lines for an easier readability are supported too.
Using a colortable is easy. Just add the colortable file to the parameter list.
Example of a colortable file:
# this is a comment
% I recomment the comment starting with #
10 255 0 0
20 56 255 0
#3 0 0 255
Parameter: -ct colortablefile.txt
Be aware, if the colortable doesn't contain values of the zmap, there are rendered black.
After selecting 'Run vlview' from the 'Options' menu or clicking the vlview icon at the toolbar, 'vlview' is
opened with the current data set.
Just by navigating through 'vlview', the 'vlrender' clipping object will follow vlview's current cursor position
as long as both programs are connected. The connection is indicated by the potted connector icon at the
toolbar of 'vlrender' and 'vlview'. (See 'Synchronize with Lipsia-Server' in the 'Options' menu or the
connector icon at the toolbar.)
In addition, changing the zmap-thresholds in 'vlview' will cause 'vlrender' to do the same if both
programs are connected.
Note: The program 'vlrender' is based on a commercial library called VGL. By using 'vlrender' the user agrees to the license terms and conditions of Volume Graphics GmbH: For more information please contact:
Volume Graphics GmbH
Wieblinger Weg 92a
D-69123 Heidelberg, Germany
Tel +49 (0)6221 7392060
Fax +49 (0)6221 7392088
info@volumegraphics.com
www.volumegraphics.com