Figure 4

Signed distance field \(\phi \left(\vec{x}\right)\): \(\phi \left(\vec{x}\right)=0\) locates on the interface Γ with inward normal \({\vec{N}}^{w}(\vec{x})\) . \(\phi \left(\vec{x}\right)<0\) and \(\phi \left(\vec{x}\right)>0\) mean inside and outside of surface Γ.