{"id":12330,"date":"2021-05-31T09:00:22","date_gmt":"2021-05-31T13:00:22","guid":{"rendered":"https:\/\/blogs.mathworks.com\/pick\/?p=12330"},"modified":"2022-05-29T21:54:39","modified_gmt":"2022-05-30T01:54:39","slug":"visualizing-earth-and-celestial-bodies","status":"publish","type":"post","link":"https:\/\/blogs.mathworks.com\/pick\/2021\/05\/31\/visualizing-earth-and-celestial-bodies\/","title":{"rendered":"Visualizing Earth and Celestial Bodies"},"content":{"rendered":"
Jiro<\/span><\/a>'s Pick this week is <\/span>3D Earth and Celestial Bodies (planet3D)<\/span><\/a> by <\/span>Tamas Kis<\/span><\/a>.<\/span><\/div>
I'm not an expert in astronomy or space mechanics, but this entry visually caught my attention. Tamas includes a thorough <\/span>documentation<\/span><\/a> with plenty of examples and the details of the implementation. The planets are defined using the <\/span>ellipsoid<\/span><\/a> function, based on astronomical data. The planets are visualized using the <\/span>surface<\/span><\/a> function, and the map (texture) of the planets is defined as the CData of the surface.<\/span><\/div>
I wanted to visualize the moon orbiting around Earth. I modified the function signature of <\/span>planet3D<\/span> to retrieve the handle of the surface object, so that I could update the location of the moon. <\/span><\/div>
function <\/span>planet_surface = planet3D(planet,position,gmst,reference_plane,units,transparency)<\/span><\/span><\/div><\/div>
Here's the animation code. Please note that the orbit of the moon is much smaller than reality, since the objects will be too small if I use actual values.<\/span><\/div>
figure<\/span><\/span><\/div><\/div>
background(<\/span>'Milky Way'<\/span>);<\/span><\/span><\/div><\/div>
planet3D(<\/span>'Earth Cloudy'<\/span>);<\/span><\/span><\/div><\/div>
light(<\/span>'Position'<\/span>,[1,-1,0]);<\/span><\/span><\/div><\/div>
<\/div><\/div>
% Place Moon at the origin<\/span><\/span><\/div><\/div>
m = planet3D(<\/span>'Moon'<\/span>,[0 0 0]);<\/span><\/span><\/div><\/div>
<\/div><\/div>
% Capture the X and Y coordinates of the surface object<\/span><\/span><\/div><\/div>
origX = m.XData;<\/span><\/span><\/div><\/div>
origY = m.YData;<\/span><\/span><\/div><\/div>
<\/div><\/div>
% Calculate the Moon trajectory. (Value is smaller than actual, for visual<\/span><\/span><\/div><\/div>
% purpose)<\/span><\/span><\/div><\/div>
xd = 50000*sin(linspace(0,2*pi,100));<\/span><\/span><\/div><\/div>
yd = 50000*cos(linspace(0,2*pi,100));<\/span><\/span><\/div><\/div>
<\/div><\/div>
% Change some camera settings<\/span><\/span><\/div><\/div>
camva(40)<\/span><\/span><\/div><\/div>
camproj(<\/span>'perspective'<\/span>)<\/span><\/span><\/div><\/div>
campos([0 -85000 30000])<\/span><\/span><\/div><\/div>
camtarget(<\/span>'manual'<\/span>)<\/span><\/span><\/div><\/div>
camup(<\/span>'manual'<\/span>)<\/span><\/span><\/div><\/div>
<\/div><\/div>
for <\/span>id = 1:length(xd)<\/span><\/span><\/div><\/div>
m.XData = origX + xd(id);<\/span><\/span><\/div><\/div>
m.YData = origY + yd(id);<\/span><\/span><\/div><\/div>
drawnow<\/span><\/span><\/div><\/div>
end<\/span><\/span><\/div><\/div><\/div>
\"3D_planets_anim.gif\"<\/img><\/div>
Give it a try, and let us know what you think<\/span> <\/span>here<\/span><\/a> <\/span>or leave a<\/span> <\/span>comment<\/span><\/a> <\/span>for Tamas.<\/span><\/div>\r\n<\/div>