Render brain and create a region of interest
User-defined region (regioin-of-interest, ROI) on a brain surface can be created manually. Remember to first set your environment variable 'SUBJECTS_DIR' correctly first. Then, you may consult the following procedures.
First, you display the brain surface.
etc_render_fsbrain;
This shows the inflated left hemisphere (of subject 'fsaverage').
Now you start creating an ROI by clicking 'o' in the brain figure. You need to define an ROI by multiple points. These points will be connected sequentially and automatically (based on the shortest path using the Dijkstra search on the underlying structural 3D brain model). The first two click may be a little bit slow because of the construction of a connected graph needed for the Dijkstra search.
Upon completing the the selection of all points, you need to press 'o' again. Now the last selected point will be automatically connected to the first selected point to form a closed region. The program will also try to fill this closed region by "flooding" over this region from an approximately center point. After completing filling the ROI, you will be prompted to save this ROI as a label file.
You can load the user-defined labels for visualization. The procedure is described at this page.