4
$\begingroup$ 
Show[
 Graphics[Polygon[{{0, 0}, {1, 0}, {1, 1}, {0, 1}},VertexColors -> {Opacity[0, Red], Opacity[1, Red], Opacity[1, Red],Opacity[0, Red]}]], 
 Graphics[Circle[{0.5, 0.5}, 0.2]]
 ]

Show[
 Graphics[{Red, Polygon[{{0, 0}, {1, 0}, {1, 1}, {0, 1}}]}],
 Graphics[Circle[{0.5, 0.5}, 0.2]]
 ]

Where the circle in first one looks bad smoothness. Any method to fix this? enter image description here

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3
  • $\begingroup$ related: Antialiasing of horizontal lines but Antialising trick doesn't work in this case (v9 and v11.3) $\endgroup$
    – kglr
    Commented Jul 28, 2018 at 6:15
  • $\begingroup$ Just as info: This is not happening in my copy of version 11.3 for macOS. $\endgroup$
    – Henrik Schumacher
    Commented Jul 28, 2018 at 8:40
  • $\begingroup$ Related: (7416) $\endgroup$
    – Mr.Wizard
    Commented Jul 29, 2018 at 3:25

3 Answers 3

Reset to default
2
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How about:

Show[
    Graphics[
        Polygon[
            {{0,0},{1,0},{1,1},{0,1}},
            VertexColors->{Opacity[0,Red],Opacity[1,Red],Opacity[1,Red],Opacity[0,Red]}
        ]
    ],
    Graphics[{Antialiasing->True,Circle[{0.5,0.5},0.2]}]
]

enter image description here

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$\endgroup$
2
$\begingroup$

Two workarounds:

Graphics[{Raster[Table[{1, 0, 0, y}, {x, 0, 1, 1/100}, {y, 0, 1, 
     1/100}], {ImageScaled[{0, 0}], ImageScaled[{1, 1}]}], 
  Circle[{.5, .5}, .2]}, PlotRange -> {{0, 1}, {0, 1}}]

enter image description here

Overlay[{Graphics[Polygon[{{0, 0}, {1, 0}, {1, 1}, {0, 1}}, 
  VertexColors -> {Opacity[0, Red], Opacity[1, Red], Opacity[1, Red], Opacity[0, Red]}]], 
  Graphics[Circle[{0.5, 0.5}, 0.2], PlotRange -> {{0, 1}, {0, 1}}]}]

enter image description here

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2
$\begingroup$

As to the "why": because once you include a Polygon with VertexColors, the graphics will be rendered by the GPU (the same as 3D graphics). This means limited support for anti-aliasing which is going to be GPU-dependent.

You can turn on anti-aliasing for such graphics in the preferences, if your GPU supports it.

enter image description here

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