struct CSplineFrame{  float x, y; // x and y position of the keyframe  float k; // Gradient at keyframe};// Calculates gradients for all keyframes.void CSpline::CalcGrads(){  for(UINT i=0; i<K.size(); i++)  {    if(0==i) // Gradient for the first keyframe      K[i].k = (K[i+1].y - K[i].y) / (K[i+1].x - K[i].x);    else if(K.size()-1 == i) // Gradient for the last keyframe      K[i].k = (K[i].y - K[i-1].y) / (K[i].x - K[i-1].x);    else // Gradient for all other keyframes.      K[i].k = .5f * (K[i].y - K[i-1].y) / (K[i].x - K[i-1].x) +               .5f * (K[i+1].y - K[i].y) / (K[i+1].x - K[i].x);  }}// Evaluates a single spline value between two keyframes, p1 and p2. // The value of t should be between 0 and 1.// Note that the result is not adjusted for irregularly spaced keyframes.// Also note that CalcGrads() needs to be called first.float CSpline::Eval(UINT p1, UINT p2, float t){  float y1 = K[p1].y;  float y2 = K[p2].y;  float k1 = K[p1].k * (K[p2].x - K[p1].x); // "Adjusted" gradient at p1  float k2 = K[p2].k * (K[p2].x - K[p1].x); // "Adjusted" gradient at p2  float tt = t*t;  float ttt= tt*t;    return y1*(2.0f*ttt - 3.0f*tt + 1.0f) + y2*(3.0f*tt-2.0f*ttt) +          k1*(ttt - 2.0f*tt + t) +           k2*(ttt - tt);}// Evaluates a series of spline values and fills the "values" vector.// dx is the increment between values along the x axis. The values are // evenly spaced, where the first and last values coincides // with the first and last keyframes.// CalcGrads() needs to be called before Eval().void CSpline::Eval(CFrameVector& values, float dx){  UINT ik=0; // Current keyframe index  UINT iv=0; // Current value index  float x = K[ik].x, y, t;  UINT nNumValues = (UINT)((K[K.size()-1].x - K[0].x)/dx);  if(values.size() != nNumValues)    values.resize(nNumValues+1);  while(x<K[K.size()-1].x && iv<nNumValues)  {    t = (x-K[ik].x)/(K[ik+1].x - K[ik].x); // Adjust spacing    y = Eval(ik, ik+1, t); // Get value at x    values[iv].x = x;    values[iv].y = y;    values[iv].k = 0;        iv+=1;    x+= dx;    if(x>=K[ik+1].x)      ik++;  }  values[nNumValues] = K[K.size()-1];  values[nNumValues].k = 0;}