How to trace shadows through 3D Gaussian scenes instantly?

3D Gaussian Splatting renders views fast but can't trace secondary rays for shadows or lighting. This work distills a Directed Distance Function—a compact neural field that answers "does this ray hit anything?" in one forward pass. The DDF stays constant-size regardless of scene complexity, runs 26–72× faster than sphere tracing, and reproduces ray-traced quality (30.3 dB for shadows) on real captured scenes. Code released.