Efficient Parallel Implementation of Active Appearance Model Fitting Algorithm on GPU

Algorithm 3

GPU-based method for calculating S.

// 𝑖: the ID of vertex.

// 𝑐: the appearance parameters vector.

// 𝑄_𝑠: the matrix describing the modes of variation.

// 𝑠₀: the mean shape vector.

// 𝑠_𝑥, 𝑠_𝑦, 𝑡_𝑥 and 𝑡_𝑦: the pose parameters.

(1) i ←blockId * gridDim + threadId;

(2)  while  𝑘 < size of c

(3)    𝑥←𝑥+𝑐[𝑘]×𝑄_𝑠[𝑘][𝑖];

(4)    𝑦←𝑦+𝑐[𝑘]×𝑄_𝑠[𝑘][𝑖+1];

(5)  end  while

(6)  𝑆[𝑖]←𝑥+𝑠₀[𝑖];

(7)  𝑆[𝑖+1]←𝑦+𝑠₀[𝑖+1];

(8)  𝑆[𝑖]←𝑠_𝑥×𝑆[𝑖]−𝑠_𝑦×𝑆[𝑖+1]+𝑡_𝑥;

(9)  𝑆[𝑖+1]←𝑠_𝑦×𝑆[𝑖]+𝑠_𝑥×𝑆[𝑖+1]+𝑡_𝑦;

(10)   check if ith vertex is in image