BarChart3D: varying individual bar color

Question

I've been working with a chart like so:

data = {{0, 0, 1}, {3, 0, 0}, {1, 0, 2}} + .001;
BarChart3D[data, ChartLayout -> "Grid", Method -> {"Canvas" -> None}, 
 Axes -> None, FaceGrids -> None, BarSpacing -> 0, 
 ViewPoint -> 1.5 {3, -2.29, 3},
 ColorFunction -> "Rainbow"]

Right now the entirety of each bar is rendered in some color based on its height. What I'd like is for the color of each bar to vary in the vertical direction, an effect similar to, for example

Plot3D[Sin[x + y^2], {x, -3, 3}, {y, -2, 2}, 
ColorFunction -> (Blend[{Yellow, Purple}, #3] &)]

where the color of any point on the surface depends only on its z position. ColorFunction seems to offer a lot of control over the colors of objects; is there a way to specify a ColorFunction for each bar, or even all bars uniformly?

kglr · Accepted Answer

You can use ChartElementDataFunction["GradientScaleCube", "ColorScheme" -> cs] as the option value for ChartElementFunction to apply a gradient scheme cs to all data.

data = {{0, 0, 1}, {3, 0, 0}, {1, 0, 2}};
options = {ChartLayout -> "Grid", Method -> {"Canvas" -> None}, 
   Axes -> None, FaceGrids -> None, BarSpacing -> 0, 
   ViewPoint -> 1.5 {3, -2.29, 3}, ImageSize -> 400};

Row[BarChart3D[data, options, 
    ChartElementFunction -> ChartElementDataFunction["GradientScaleCube", 
      "ColorScheme" -> #]] & /@ {"Rainbow", "SolarColors"}]

is there a way to specify a ColorFunction for each bar

You can wrap each data set or each data point with the ChartElementFunction you wish to use. With "GradientScaleCube" as the ChartElementFunction you can inject your desired ColorFunction for a bar as the "ColorScheme" option:

data2 = {{0, 0, 1} -> ChartElementDataFunction["SquareWaveCube", 
     "AngularFrequency" -> 10, "RadialAmplitude" -> 0.26], 
   {3, 0, 0} -> ChartElementDataFunction["GradientScaleCube", 
     "ColorScheme" -> "Rainbow"],
   {1, 0, 2} -> ChartElementDataFunction["SegmentScaleCube", 
     "ColorScheme" -> "DarkRainbow"]};
data3 = {{0, 0, 1 -> ChartElementDataFunction["GradientScaleCube", 
      "ColorScheme" -> "Rainbow"]},
     {3 -> ChartElementDataFunction["GradientScaleCube", 
      "ColorScheme" -> "Rainbow"], 0, 0}, 
     {1, 0, 2 -> ChartElementDataFunction["SegmentScaleCube", 
      "ColorScheme" -> "DarkRainbow"]}};

Row[BarChart3D[#, options, 
    ChartElementFunction -> (If[#3 =!= {}, #3[[1]][#], 
        ChartElementDataFunction["DoubleProfileCube"][##]] &)] & /@ {data2, data3}]

Update: Using custom ChartElementFunctions to inject bar-specific color functions through metadata wrappers:

dt = Reverse[Range[3]] # & /@ Range[3];
grads = RandomChoice[ColorData["Gradients"][[11 ;; 16]], 9];

To use color gradients as metadata, use pointi -> colorgradiendti to assign colorgradiendti  to pointi:

dt1 = Partition[Rule @@@ Transpose[{Flatten@dt, grads}], 3];

and define the custom ChartElementFunction as:

cedF1 = ChartElementDataFunction["GradientScaleCube", 
     "ColorScheme" -> If[#3 =!= {}, #3[[1]], "Pastel"]][##] &;

To use ChartElementFunction as metadata, use pointi -> ChartElementDataFunction["GradientScaleCube", 
      "ColorScheme" -> colorgradiendti] to assign colorgradiendti  to pointi:

dt2 = Partition[Rule @@@ Transpose[{Flatten@dt, 
      ChartElementDataFunction["GradientScaleCube", "ColorScheme" -> #] & /@ grads}], 3];

and define the custom ChartElementFunction as:

cedF2 = #3[[1]][##] &;

Example:

Row[{BarChart3D[dt1, options, ChartElementFunction -> cedF1], 
  BarChart3D[dt2, options, ChartElementFunction -> cedF2]}]

BarChart3D: varying individual bar color

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