Fourth Power

Continuing the series of conformal transformations (1, 2, 3). The first part shows a square grid in the first quadrant under the transformation $z \mapsto z^t$ as $t$ varies from 1 to 4, reflected through the line $y=-x$. The power is then reduced back to 1, but for the fourth quadrant rather than the first.

This part makes use of @J. M.'s rational smoothstep function for smooth easing:

ssteprat = #^3/(1 - 3 # (1 - #)) &;

And here's the rest of the code for this part:

DynamicModule[{width = .01, n = 16, m = 100, s, sign, 
  cols = RGBColor /@ {"#ffeb00", "#457c39"}},
 Manipulate[
  s = ssteprat[1 - Abs[1 - t]];
  sign = 2 UnitStep[t - 1] - 1;
  Graphics[{
    FaceForm[cols[[1]]],
    Table[
     Polygon[
      Join @@ Transpose[
        Table[
         ReIm[-I (#/1.2)^(3 s + 1)] & /@ {x + sign I (y - width), 1 - x + sign I (y + width)},
         {x, -width, 1 + width, (1 + 2 width)/m}]]],
     {y, 0, 1, 1/n}],
    Table[
     Polygon[
      Join @@ Transpose[
        Table[
         ReIm[-I (#/1.2)^(3 s + 1)] & /@ {x - width + sign I y, x + width + sign I (1 - y)},
         {y, -width, 1 + width, (1 + 2 width)/m}]]],
     {x, 0, 1, 1/n}]},
   PlotRange -> {{-2, 2}, {-1.5, 2.5}}, ImageSize -> 540, 
   Background -> cols[[-1]]],
  {t, 0, 2}]
 ]

The last part of the animation is just a simple $90^\circ$ rotation of the grid, but with a little bounce effect, which is realized by the following function:

EaseOutBounce[t_] := Piecewise[{{7.5625 t^2, t < 1/2.75},
   {7.5625 (t - 1.5/2.75)^2 + 0.75, t < 2/2.75},
   {7.5625 (t - 2.25/2.75)^2 + 0.9375, t < 2.5/2.75},
   {7.5625 (t - 2.625/2.75)^2 + 0.984375, True}}];

This is a translation to Wolfram Language of Emmanuel Oga's implementation of one of Robert Penner's easing functions, which you can see nicely visualized at easings.net (incidentally, I would be very interested to know if anybody has already implemented all of these [or similar] easing functions in Wolfram Language).

Here's the code for this part:

DynamicModule[{width = .01, n = 16, m = 100, s, 
  cols = RGBColor /@ {"#ffeb00", "#457c39"}},
 Manipulate[
  s = EaseOutBounce[t];
  Graphics[{
    FaceForm[cols[[1]]],
    Table[
     Polygon[
      Join @@ Transpose[
        Table[
         ReIm[E^(-I ?/2 (1 + s)) #/1.2] & /@ {x + I (y - width), 1 - x + I (y + width)},
         {x, -width, 1 + width, (1 + 2 width)/m}]]],
     {y, 0, 1, 1/n}],
    Table[
     Polygon[
      Join @@ Transpose[
        Table[
         ReIm[E^(-I ?/2 (1 + s)) #/1.2] & /@ {x - width + I y, x + width + I (1 - y)},
         {y, -width, 1 + width, (1 + 2 width)/m}]]],
     {x, 0, 1, 1/n}]},
   PlotRange -> {{-2, 2}, {-1.5, 2.5}}, ImageSize -> 540, 
   Background -> cols[[-1]]],
  {t, 0, 1}]
 ]