X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;ds=sidebyside;f=primer.c;h=f023b10365881f25c3de3f4e7b9a23e3bc2c4586;hb=b462f455cbaa1d716ff6d7b83ae4e1092ba3092a;hp=3d9244a60f0b497a7cbe775b28ed2eebe1ed2de0;hpb=62f97dcbc53754ef8a81add86946e54825c4c096;p=moebius2.git

diff --git a/primer.c b/primer.c
index 3d9244a..f023b10 100644
--- a/primer.c
+++ b/primer.c
@@ -21,7 +21,9 @@ int main(int argc, const char **argv) {
     double u= y * 1.0 / (Y-1); /* SGT's u runs 0..1 across the strip */
 
     /* SGT's v runs 0..pi along the strip, where the join is at 0==pi.
-     * So that corresponds to 0..X (since 0==X in our scheme). */
+     * So that corresponds to 0..X (since 0==X in our scheme).
+     * Vertices with odd y coordinate are halfway to the next x coordinate.
+     */
     double v= (x*2 + (y&1)) * M_PI / (X*2);
 
     K printf("print %c%c( %-*.*g, %-*.*g);  # %03x %2d %2d\n",