ColorFunction makes choppy line in Plot

Question

I'm trying to apply a ColorFunction[] to a piecewise plot. For some reason, applying the ColorFunction[] to a plot results in aliasing artifacts (as seen in the image). Is there anyway to get rid of this? (Mathematica 11.0)

cf[x_] := If[x <= 0, Black, Blue];
Rasterize[
 Column[{
   Plot[Piecewise[{{x^2, x >= 0}, {0, x < 0}}], {x, -2, 2}, 
    ColorFunction -> cf, ImageSize -> Large],
   Plot[Piecewise[{{x^2, x >= 0}, {0, x < 0}}], {x, -2, 2}, 
    PlotStyle -> Blue, ImageSize -> Large]
   }], ImageSize -> Large]

Answer 1

You can use MeshShading instead of ColorFunction

Rasterize[
 Column[{Plot[Piecewise[{{x^2, x >= 0}, {0, x < 0}}], {x, -2, 2}, 
    Mesh -> {{0}}, MeshShading -> {Black, Blue}, ImageSize -> Large], 
   Plot[Piecewise[{{x^2, x >= 0}, {0, x < 0}}], {x, -2, 2}, 
    PlotStyle -> Blue, ImageSize -> Large]}], ImageSize -> Large]