# Triangular pattern in plot faces [duplicate]

I am trying to export this figure to pdf:

r1 = RegionPlot[
x + 4 >= y^2 && y <= 1 && x <= 0, {x, -4, 4}, {y, -4, 4},
PlotStyle -> {Red, Opacity[0.5]}, MaxRecursion -> 8,
Axes -> {True, True}, AxesLabel -> {"D(E)", "E"},  Ticks -> None];
r2 = RegionPlot[
4 - x >= (y - 1)^2 && y <= 1 && x >= 0, {x, -4, 4}, {y, -4, 4},
MaxRecursion -> 8];
fermi = Plot[1, {x, -4, 4}, PlotStyle -> {{Gray, Dashed}},
PlotLegends -> LineLegend[{Dashed}, {"Fermi level"}]];
p1 = Show[{r1, r2, fermi,
Graphics[{Arrowheads[{-.03, .03}], Arrow[{{0, -2}, {0, -1}}]}],
Graphics[Text[Style["I", Large], {0.3, -1.5}]]}, Frame -> None]

using

Export[NotebookDirectory[] <> "exchange_splitting.pdf", p1]

while it looks very nice in Mathematica, it has a weired pattern in the resulting pdf. The red area seems to be made up of little triangles. It's the same for the blue area, but it's less visible. How can I create a pdf without this effect. If this isn't possible, any vector graphic feasible for Latex will do as well.

• See this and this. – halirutan Jan 12 '18 at 15:17
• The filled regions are made of little triangles. That's the problem basically. A quick fix would be an export to a bitmap file format, e.g. PNG. – Henrik Schumacher Jan 12 '18 at 15:37
• I use Mathematica 11 and even if I try the suggested solutions it doesn't solve the problem. PNG works fine, but I would like to use somekind of vector graphic. – Stein Jan 12 '18 at 15:54