Implementation thinking ·Simple question: f无xi How to compute (in 3D? How about the gradient in tetrahedral mesh? Implementation thinking • Simple question: How to compute 𝒙𝑘 − 𝒙𝑗 ⊥ in 3D? • How about the gradient in tetrahedral mesh? 𝑓𝑖 𝑓𝑗 𝑓𝑘 𝒙𝑗 𝒙𝑘 𝒙𝑖 𝒙