message: always initialize DG tangents in postIntersect
diff: @@ -77,6 +77,11 @@ inline void postIntersect(uniform Model *uniform model,
  if (flags & DG_COLOR)
  dg.color = make_vec4f(1.f);
  + if (flags & DG_TANGENTS) {
  + dg.dPds = make_vec3f(1.f, 0.f, 0.f);
  + dg.dPdt = make_vec3f(0.f, 1.f, 0.f);
  + }
  +
  dg.P = ray.org + ray.t * ray.dir;
  dg.epsilon = getIntersectionError(dg.P, ray.t);
  