It s not work with me what is writng in the manual off SPM8:
For the “Render” option we ﬁrst created a rendering for this subject. This was implemented
• “Normalise (Write)” the two images c1sM00223 002.img and c2sM00223 002.img using the
“Parameter File ” sM00223 002 seg sn.mat and a voxel size of [1 1 3].
• Selecting “Xtract Surface” from the “Render” pulldown menu.
• Selecting the gray and white matter images wc1sM00223 002.img and wc2sM00223 002.img
created in the ﬁrst step.
• Saving the results using the default options (Rendering and Surface).