e97e5d31d0
This approximation is equivalent to the exact SDF on the surface and externally, but it is smooth on the inside, rotating the gradient from radial at the box center to normal to the faces at the surface, and interpolated linearly (using two Euler angles) in between. This enables stable contact gradients for deeper penetrations. PiperOrigin-RevId: 776574022 Change-Id: I562976e9f0535b0067aa12b2bc9d48eccb6472e9