Plot area with equation
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Hello everyone,
I want to plot an area on a sphere, which is defined with the following equations:
R = 50
could somebody help?
Best regards
Alex
采纳的回答
Abdolkarim Mohammadi
2020-7-17
编辑：Abdolkarim Mohammadi
2020-7-18
r = 50;
NumPoints = 500;
[UnitX,UnitY,UnitZ] = sphere (NumPoints);
RealX = r * UnitX;
RealY = r * UnitY;
RealZ = r * UnitZ;
x = RealX(:);
y = RealY(:);
z = RealZ(:);
Mask = 2.*y .* (sqrt(r.^2-x.^2-y.^2)./(r.^2)).* sind(15) ...
+ ((r.^2-2*x.^2-2*y.^2)./(r.^2)) .* cosd(15) ...
>= cosd(5.8);
% ----------------
figure ('Position', [62,182,1172,338]);
MaskPatchPositive = all ([Mask,z>0], 2);
MaskPatchNegative = all ([Mask,z<0], 2);
% ----------------
subplot (1,3, 1);
hold on
surf (RealX,RealY,RealZ, ...
'EdgeAlpha', 0.05, ...
'FaceAlpha', 0.05);
scatter3 (x(Mask),y(Mask),z(Mask),9, ...
'MarkerEdgeColor', 'none', ...
'MarkerFaceColor', 'r');
hold off
view ([-35,45]);
grid ('on');
box ('on');
daspect ('auto');
ax = gca;
ax.BoxStyle = 'full';
title ('All points');
% ----------------
subplot (1,3, 2);
hold on
surf (RealX,RealY,RealZ, ...
'EdgeAlpha', 0.1, ...
'FaceAlpha', 0.1);
scatter3 (x(MaskPatchPositive),y(MaskPatchPositive),z(MaskPatchPositive),9, ...
'MarkerEdgeColor', 'none', ...
'MarkerFaceColor', 'r');
hold off
xlim ([-5,5]);
ylim ([0,15]);
zlim ([45,50]);
grid ('on');
box ('on');
daspect ([1,1,1]);
view ([-60,30]);
ax = gca;
ax.BoxStyle = 'full';
title ('Upper part');
% ----------------
subplot (1,3, 3);
hold on
surf (RealX,RealY,RealZ, ...
'EdgeAlpha', 0.1, ...
'FaceAlpha', 0.1);
scatter3 (x(MaskPatchNegative),y(MaskPatchNegative),z(MaskPatchNegative),9, ...
'MarkerEdgeColor', 'none', ...
'MarkerFaceColor', 'r');
hold off
xlim ([-5,5]);
ylim ([0,15]);
zlim ([-50,-45]);
grid ('on');
box ('on');
daspect ([1,1,1]);
view ([-60,30]);
ax = gca;
ax.BoxStyle = 'full';
title ('Lower part');
3 个评论
Alex Lee
2020-7-18
Abdolkarim Mohammadi
2020-7-18
编辑：Abdolkarim Mohammadi
2020-7-18
You are right. I read the post again and realized that I wrote the condition for = cos(5.8) mistakenly, instead of >= cos(5.8). I revised the code and plots and there is no need for Epsilon anymore. You can increase NumPoints to get better accuracy. If the new code is correct, please mark it as the accepted answer. Thanks.
Alex Lee
2020-7-18
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