Fixes rendering of lines along z-axis, mentioned in #63

Author: ekatrukha

code/chapter-09/linestrip-3d-better.py

@@ -45,10 +45,10 @@
     vec2 t1 = normalize(screen_next.xy - screen_curr.xy);
     vec2 n1 = vec2(-t1.y, t1.x);
     v_uv = vec2(uv.x, uv.y*w);
-    if (prev.xy == curr.xy) {
+    if (prev.xyz == curr.xyz) {
         v_uv.x = -w;
         position = screen_curr.xy - w*t1 + uv.y*w*n1;
-    } else if (curr.xy == next.xy) {
+    } else if (curr.xyz == next.xyz) {
         v_uv.x = linelength+w;
         position = screen_curr.xy + w*t0 + uv.y*w*n0;
     } else {

code/chapter-09/linestrip-3d.py

@@ -35,10 +35,10 @@
     vec2 t1 = normalize(screen_next.xy - screen_curr.xy);
     vec2 n1 = vec2(-t1.y, t1.x);
     v_uv = vec2(uv.x, uv.y*w);
-    if (prev.xy == curr.xy) {
+    if (prev.xyz == curr.xyz) {
         v_uv.x = -w;
         position = screen_curr.xy - w*t1 + uv.y*w*n1;
-    } else if (curr.xy == next.xy) {
+    } else if (curr.xyz == next.xyz) {
         v_uv.x = linelength+w;
         position = screen_curr.xy + w*t0 + uv.y*w*n0;
     } else {