mimic a image frame

When I read a paper, I found a image just like following:

I don't care about the real curve functions, I only want drawing like it. So I try to coding:

g1 = RegionPlot[y > 3 x^2, {x, 0, 1}, {y, 0, 1}, PlotStyle -> LightBlue, BoundaryStyle -> Directive[Orange]];
g2 = RegionPlot[y > 2 x^2, {x, 0, 1}, {y, 0, 1}, PlotStyle -> LightYellow, BoundaryStyle -> Directive[Red, Dashed], FrameStyle -> Directive[Black, 16]];
Show[g2, g1]


My questions are: 1. How to drawing the black frame like the first image? 2. Mesh option will achieve this grids effect? 3. Mesh->All will affect the BoundaryStyle option?

g1 = RegionPlot[y > 3 x^2, {x, 0, 1}, {y, 0, 1},
PlotStyle -> Directive[EdgeForm[LightGray], LightBlue],
BoundaryStyle -> Orange];

g2 = RegionPlot[y > 2 x^2, {x, 0, 1}, {y, 0, 1},
PlotStyle -> Directive[EdgeForm[LightGray], LightYellow],
BoundaryStyle -> Directive[Red, Dashed],
FrameStyle -> Directive[Black, 16]];

g3 = RegionPlot[True, {x, 0, 1}, {y, 0, 1}, PlotStyle -> None,
BoundaryStyle -> Directive[Thick, Black]];

Show[g2, g1, g3]


You can use a single RegionPlot to get the same picture:

RegionPlot[{y > 2 x^2, y > 3 x^2, True}, {x, 0, 1}, {y, 0, 1},
FrameStyle -> Directive[Black, 16],
PlotStyle -> {Directive[EdgeForm[LightGray], LightYellow],
Directive[EdgeForm[LightGray], LightBlue], None},
BoundaryStyle -> {2 -> Directive[Orange],
1 -> Directive[Red, Dashed], 3 -> Directive[Black, Thick]}]


same picture

Alternatively, you can add the black rectangle using Epilog:

RegionPlot[{y > 2 x^2, y > 3 x^2}, {x, 0, 1}, {y, 0, 1},
FrameStyle -> Directive[Black, 16],
PlotStyle -> {Directive[EdgeForm[LightGray], LightYellow],
Directive[EdgeForm[LightGray], LightBlue]},
BoundaryStyle -> {2 -> Directive[Orange], 1 -> Directive[Red, Dashed]},
Epilog -> {EdgeForm[{Black, Thick}], FaceForm[], Rectangle[]}]


same picture

• Thanks, the results are very similar. Commented Dec 4, 2019 at 16:22
• @zongxian notice the meshing is higher around only the overlapping portions, maybe that will help you. This is awesome publication level graphics @kglr!! Commented Dec 5, 2019 at 3:10