X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=moebius2.git;a=blobdiff_plain;f=project.c;h=266237f90b222be270b723c5845007ff85330e36;hp=a2e3f9124f3fc005f05cf4864bc67f1572ed706a;hb=3228a46c1c7d345262324cad037d65cf7bbd62a4;hpb=91ec108d9464db3c09a21494469490f80a18b596

diff --git a/project.c b/project.c
index a2e3f91..266237f 100644
--- a/project.c
+++ b/project.c
@@ -76,10 +76,14 @@ static void generate_display_list(void) {
 }    
 
 static int dl_compare(const void *tav, const void *tbv) {
+  int i;
   const Triangle *const *tap= tav, *ta= *tap;
   const Triangle *const *tbp= tbp, *tb= *tbp;
-  double za= ta->vertex[0][2];
-  double zb= tb->vertex[0][2];
+  double za=0, zb=0;
+  for (i=0; i<3; i++) {
+    za += ta->vertex[i][2];
+    zb += tb->vertex[i][2];
+  }
   return za > zb ? -1 :
          za < zb ? +1 : 0;
 }