Plotting far away objects in a 3D plot

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Pablo
Pablo on 25 Dec 2022
Edited: Pablo on 26 Dec 2022
I have the 3D plot of an orbit around the Earth and the surface plot of the Earth itself. I want to see the Sun in the right spot too, but if I plot the surface plot of the Sun, the plot zooms out too much. I want to see only objects near Earth, while being able to spot the Sun in the distance. Do you have any tips to achieve that?
I have the relative position of the Sun wrt the Earth, the Earth center is the origin of the plot.
P.S.: I can zoom in the plot but results are not nearly good enough. Earth is so small that the zoom stops working before reaching it
This is the plot as of now:
This is the plot without the Sun:
This is the code (plot only):
figure('Color','k');
%rotate3d;
% Black background and planets
%background('Black');
%hold on
% Celestial bodies
p3Dopts.Units = 'km';
%p3Dopts.RotAngle = 180;
planet3D('Earth', p3Dopts);
hold on
%p3Dopts.Position = rSun(1,:)';
%planet3D('Sun', p3Dopts);
% Flight path
scatter3( Y(:,1), Y(:,2), Y(:,3), 6, scaledT)
xlabel('x [km]'); ylabel('y [km]'); zlabel('z [km]');
ylim([-40000,40000]);
title('Earth equatorial frame', 'FontSize', 14);
cbar = colorbar; cbar.Color = 'w'; cbar.Title.Color = 'w';
cbar.Title.String = strcat('Time [',Tname,']');
clim([min(scaledT);max(scaledT)])
axis equal;
grid on;
ax = gca; ax.Color = 'k'; ax.GridColor = 'w';
ax.GridAlpha = 0.45; ax.XColor = 'w'; ax.YColor = 'w';
ax.ZColor = 'w';
hold off

Accepted Answer

Pablo
Pablo on 26 Dec 2022
Edited: Pablo on 26 Dec 2022
I ended up doing a mixture of solutions. Thanks @Marco, @Cris Luengo from stackoverflow and @Karim from matlab's forum.
- r is the camera position relative to the origin like everything else
- dist is half the distance of one of the sides of the cube displayed. I decided to use the orbital height multiplied by tan(68º), based on human horizontal FOV
- rSun is the position vector of the sun
- rMoon (drawing this one too) is the position vector of the moon
First of all I have an infinite light source with the position of the sun.
To draw a far away surface object like the moon I place it with a special rMoon2 that locates it in the edge of the plot and multiply its size by a proportional number:
rMoon2 = rMoon/norm(rMoon)*dist
size = size*(dist-norm(r))/(norm(rMoon)-norm(r))
If the object is extremely far away like the sun you can drop the denominator's r.
If the object is itself a light source (the sun), you need another light source (but local) between the observer located in r, and the sun. So additionally to earlier steps you need:
localLightPos = rSun2*(1-2*tand(34/60)*(dist-norm(r))/dist))
Where 2*tand(34/60)*(dist-norm(r)/dist) is twice the radius of the apparent sun relative to the distance between sun and observer.
Here is the entire code for the plot in case you want it.
r = Y(j,1:3);
dist = tand(68)*(norm(r)-Rearth);
figure('Color','k','Position');
% Celestial bodies
p3Dopts.Units = 'km';
p3Dopts.RotAngle = angleEarth(j);
planet3D('Earth', p3Dopts);
hold on
p3Dopts = rmfield(p3Dopts, 'RotAngle');
p3Dopts.Position = rSun(j,:)/norm(rSun(j,:))*dist';
relDist = 2.1*(dist-norm(r)); % 2.1 because the sun appears bigger than it is
p3Dopts.Size = relDist/norm(rSun(j,:));
planet3D('Sun', p3Dopts);
%Sunlight, apparent Sun is ~28-34 arc minutes near Earth
light("Style","infinite","Position",p3Dopts.Position)
light("Style","local","Position",p3Dopts.Position*(1-2*tand(34/60)*relDist/dist));
p3Dopts.Position = rMoon(j,:)/norm(rMoon(j,:))*dist';
p3Dopts.Size = relDist/norm(rMoon(j,:)-r);
planet3D('Moon', p3Dopts);
p3Dopts = rmfield(p3Dopts, 'Position');
p3Dopts = rmfield(p3Dopts, 'Size');
% Ground track
scatter3( trackT(1:j,1), trackT(1:j,2), trackT(1:j,3), 12, T(1:j), 'filled')
%xlabel('x [km]'); ylabel('y [km]'); zlabel('z [km]');
title('Earth focused animation');
axis equal;
grid on;
ax = gca; ax.Color = 'k'; ax.GridColor = 'k';
ax.GridAlpha = 0; ax.XColor = 'k'; ax.YColor = 'k';
ax.ZColor = 'k';
ax.CameraPosition = r; % Set the camera position
ax.XLim = [-dist, dist]; % Set the x-axis range
ax.YLim = [-dist, dist]; % Set the y-axis range
ax.ZLim = [-dist, dist]; % Set the z-axis range

More Answers (1)

Karim
Karim on 25 Dec 2022
Those are some amazing plots!
One method that could work is to insert a "break" in the axis, i.e. hiding a part of the space between the sun and the earth.
  1 Comment
Pablo
Pablo on 26 Dec 2022
Thanks! Definitely need to explore this option. I ended up going plotting a proportional sun inside the bouding box i give because i think the axis break would still need me to scale down the surface.
More details in a separate answer, but thanks karim!

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