Colors. Lines.

src/geom.c

@@ -24,3 +24,8 @@ bool tri_within(Pt pt, Tri* tri) {
     double c = 1 - a - b;
     return 0 <= a && a <= 1 && 0 <= b && b <= 1 && 0 <= c && c <= 1;
 }
+
+Pt tri_center(Tri* tri) {
+    return (Pt){(tri->a.x + tri->b.x + tri->c.x) / 3.0,
+                (tri->a.y + tri->b.y + tri->c.y) / 3.0};
+}