code: public static float triArea2D(float[] verts, int a, int b, int c) {
          float abx = verts[b] - verts[a];
          float abz = verts[b + 2] - verts[a + 2];
          float acx = verts[c] - verts[a];
          float acz = verts[c + 2] - verts[a + 2];
          return acx * abz - abx * acz;
      }
docs: / @return The signed xz-plane area of the triangle.