X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=moebius2.git;a=blobdiff_plain;f=view.c;fp=view.c;h=cfa39753f1e89d29329ce115d1328c98c9914f57;hp=72ea2372f81c90d66e372e583d9fb83925e9ae78;hb=62f97dcbc53754ef8a81add86946e54825c4c096;hpb=d9aa142b98fffa94e33f47056090d42f8d6afae3

diff --git a/view.c b/view.c
index 72ea237..cfa3975 100644
--- a/view.c
+++ b/view.c
@@ -54,6 +54,8 @@ static void transform_coordinates(void) {
   }
 }
 
+static int vertex_in_triangles[N], vertex_in_triangles_checked;
+
 static void addtriangle(int va, int vb, int vc) {
   Triangle *t= &trisbuffer[ntris];
   int k;
@@ -64,23 +66,41 @@ static void addtriangle(int va, int vb, int vc) {
     t->vertex[1][k]= conformation[vb][k];
     t->vertex[2][k]= conformation[vc][k];
   }
+  if (!vertex_in_triangles_checked) {
+    vertex_in_triangles[va]++;
+    vertex_in_triangles[vb]++;
+    vertex_in_triangles[vc]++;
+  }
   displaylist[ntris++]= t;
 }
 
 static void generate_display_list(void) {
-  int vb, ve[3], e;
+  int vb, ve[V6], e;
 
   ntris= 0;
   FOR_VERTEX(vb) {
-    /* We use the two triangles in the parallelogram vb, vb+e0, vb+e1, vb+e2.
+    /* We use the two triangles in the parallelogram vb, vb+e5, vb+e0, vb+e1.
      * We go round each triangle clockwise (although our surface is non-
-     * orientable so it shouldn't matter).
+     * orientable so it shouldn't matter).  Picking the parallelogram
+     * to our right avoids getting it wrong at the join.
      */
-    for (e=0; e<3; e++) ve[e]= EDGE_END2(vb,e);
-    if (ve[1]>=0) {
-      if (ve[0]>=0) addtriangle(vb,ve[0],ve[1]);
-      if (ve[2]>=0) addtriangle(vb,ve[1],ve[2]);
+    for (e=0; e<V6; e++) ve[e]= EDGE_END2(vb,e);
+    assert(ve[0]>=0);
+    if (ve[5]>=0) addtriangle(vb,ve[0],ve[5]);
+    if (ve[1]>=0) addtriangle(vb,ve[1],ve[0]);
+  }
+
+  if (!vertex_in_triangles_checked) {
+    int v, expd;
+    FOR_VERTEX(v) {
+      expd= RIM_VERTEX_P(v) ? 3 : 6;
+      if (vertex_in_triangles[v] != expd) {
+	fprintf(stderr,"vertex %02x used for %d triangles, expected %d\n",
+		v, vertex_in_triangles[v], expd);
+	abort();
+      }
     }
+    vertex_in_triangles_checked= 1;
   }
 }    
 
@@ -578,6 +598,23 @@ static void check_input(void) {
   show();
 }
 
+static void topocheck(void) {
+  int v1,e,v2,eprime,v1prime, count;
+  FOR_EDGE(v1,e,v2) {
+    count= 0;
+    FOR_VEDGE(v2,eprime,v1prime)
+      if (v1prime==v1) count++;
+    if (count!=1) {
+      fprintf(stderr,"%02x -%d-> %02x  reverse edge count = %d!\n",
+	      v1,e,v2, count);
+      FOR_VEDGE(v2,eprime,v1prime)
+	fprintf(stderr,"%02x -%d-> %02x -> %d -> %02x\n",
+		v1,e,v2,eprime,v1prime);
+      exit(-1);
+    }
+  }
+}
+
 int main(int argc, const char *const *argv) {
   static const int wantedevents= POLLIN|POLLPRI|POLLERR|POLLHUP;
 
@@ -585,6 +622,9 @@ int main(int argc, const char *const *argv) {
   int k, i, r, *xfds, nxfds, polls_alloc=0;
   struct pollfd *polls=0;
   int motion_deferred=0, motion_x=-1, motion_y=-1;
+
+  topocheck();
+  if (argc==1) { printf("topology self-consistent, ok\n"); exit(0); }
   
   if (argc != 2 || argv[1][0]=='-') {
     fputs("need filename\n",stderr); exit(8);