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I'm attempting to combine two problems that were previously addressed in the questions below:

  1. Filling an area between two curves with respect to a color function

Adding a gradient filling according to a given function between two curves

Can I make a plot with gradient filling?

  1. Rotating a plot, something trivial which I find ridiculously difficult doing in mathematica

How do I rotate a curve?

How to rotate the curve but not the axes?

Here is an example, in which I've tried to simplify as much as possible from my own problem:

Consider the two following curves

    list1 = {2.6, 3.9, 5.0, 6.3, 7.6, 8.7, 10.0, 11.3, 12.4, 13.7, 15.0, 
   16.1, 17.5, 18.6, 19.8, 21.1};
list2 = {0.9, 1.0, 1.3, 4.4, 4.5, 4.9, 7.9, 8.0, 8.6, 11.4, 11.5, 
   14.7, 14.8, 15.1, 18.2, 18.3};
f1 = Interpolation[
   Thread[{Table[i, {i, 0, 3, N[3/(Length[list1] - 1)]}], list1}]];
f2 = Interpolation[
   Thread[{Table[i, {i, 0, 3, N[3/(Length[list2] - 1)]}], list2}]];
Plot[{f1[t], f2[t]}, {t, 0, 3}]

enter image description here

I would like to fill the area between them with a function that changes with repsect to the distance between the two curves:

    tmp2 = Table[i, {i, 0, 5, 0.1}];
Y = Interpolation[
  Thread[{tmp2, Table[Sqrt[r], {r, 0, 1, N[1/(Length[tmp2] - 1)]}]}]]
Plot[Y[z], {z, 0, 5}]

enter image description here

c[x_, y_, z_] := (y Exp[-2 y x])/( 1 + y Exp[-2 y z ]) 
Plot[c[x, Y[1], 1], {x, 0, 2}, PlotRange -> All, 
 PlotStyle -> Thickness[0.025], 
 ColorFunction -> 
  Function[{x}, 
   Blend[{ColorData["TemperatureMap", 0], 
     ColorData["TemperatureMap", 1]}, c[x, Y[2], 2]]]]
Plot[c[x, Y[4], 4], {x, 0, 4}, PlotRange -> All, 
 PlotStyle -> Thickness[0.025], 
 ColorFunction -> 
  Function[{x}, 
   Blend[{ColorData["TemperatureMap", 0], 
     ColorData["TemperatureMap", 1]}, c[x, Y[4], 4]]]]

enter image description here

As u can see above, the Profile of the function is dependent on the distance between the two curves, both directily, and in-directly with Y.

I would like to have this profile rotated, with the horizontal filling between the two rotated curves is given by the function above, something like:

enter image description here

Here are my abortive attempts so far

    Plot[{f1[t], f2[t]}, {t, 0, 3}, Filling -> {1 -> {2}}, 
 ColorFunctionScaling -> False, 
 ColorFunction -> 
  Function[{x, y}, 
   Blend[{ColorData["TemperatureMap", 0], 
     ColorData["TemperatureMap", 1]}, 
    c[(y - f2[x])/(f1[x] - f2[x]), Y[f1[x] - f2[x]], f1[x] - f2[x]]]]]
pp1 = Plot[{f1[t], f2[t]}, {t, 0, 3}]
axisRotate = # /. {x_Point | x_Line | x_GraphicsComplex :> 
      MapAt[(#.{{0, -1}, {1, 0}}) &, x, 1]} &;
Show[axisRotate@pp1, PlotRange -> {{10, 30}, {-5, 0}}, 
 AspectRatio -> GoldenRatio/1]

Any help will be appreciated.

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Are you looking for something like this?

list1 = {2.6, 3.9, 5.0, 6.3, 7.6, 8.7, 10.0, 11.3, 12.4, 13.7, 15.0, 16.1, 17.5, 18.6, 19.8, 21.1};
list2 = {0.9, 1.0, 1.3, 4.4, 4.5, 4.9, 7.9, 8.0, 8.6, 11.4, 11.5, 14.7, 14.8, 15.1, 18.2, 18.3};
f1 = Interpolation[ Transpose[{Subdivide[0., 3., Length[list1] - 1], list1}]];
f2 = Interpolation[ Transpose[{Subdivide[0., 3., Length[list2] - 1], list2}]];
g1 = ParametricPlot[
  RotationMatrix[-Pi/2].{t, f1[t] (1 - s) + s f2[t]},
  {t, 0, 3}, {s, 0, 1},
  AspectRatio -> 1/2,
  ColorFunction -> Function[{x, y, t, s}, ColorData["Rainbow"]@Sqrt[s]],
  BoundaryStyle -> Directive[Dashed, Black]
  ]

enter image description here

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  • $\begingroup$ Thanks for your answer, I'm trying to implement it with my function as described above. Why did you use {x,y,t,s} in the ColorFunction, isn't {x,y} sufficient? $\endgroup$ – jarhead May 11 '18 at 14:44
  • $\begingroup$ The rotation works fine, but I can't manage to work out the parameter 's' into the function 'c' above. Also the range between the colordata between the two curves does not range between [0,1]. Can you provide a solution with my definitions? $\endgroup$ – jarhead May 11 '18 at 14:54
  • $\begingroup$ ColorFunctions in 2D are assumed to take 4 arguments: The first two are the actual coordinates with respect to the coordinate system in the ambient space; the latter two are the coordinates within the parameterization domain. So just write down the color you want in terms of x, y, s, and t and you are done. $\endgroup$ – Henrik Schumacher May 11 '18 at 15:15
  • $\begingroup$ Thanks, but this does not work out using the function I defined in the question. Can you show how you do this please with that function? $\endgroup$ – jarhead May 11 '18 at 15:37
  • $\begingroup$ If you cannot write down what you want how should I do? I simply don't understand what you are asking. Really, your question is overly complicated and contains lots of convoluted code that has nothing to do with the core of the question. Please ask yourself: Which color should a point with coordinates {x,y} obtain? Write that down as a function that takes values between 0 and 1. Have also a look at the option ColorFunctionScaling. $\endgroup$ – Henrik Schumacher May 11 '18 at 16:16

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