I am currently trying to plot 3D streamtubes. I want the tubes to be colored corresponding to their respective velocity (e.g. slow = blue, fast = red).
To be more exact, I have three 3D-matrices containing the velocity in x, y and z direction. The color of the streamtubes should be sqrt(vx^2+vy^2+vz^2). When using streamtube(x,y,z,vx,vy,vz,sx,sy,sz) the tubes are colored according to their z-coordinate which is useless because it's a 3D plot anyway.
Well this wasn't easy (it ought to be a builtin option), but by modifying the CData of each tube (they are each their own graphics object), you can achieve the desired result. Here's an example
load wind
[sx,sy,sz] = meshgrid(80,20:10:50,0:5:15);
h=streamtube(x,y,z,u,v,w,sx,sy,sz);
drawnow
view(3)
axis tight
shading interp;
This gives this picture:
but then doing this:
vel=sqrt(u.^2+v.^2+w.^2); %// calculate velocities
for i=1:length(h)
%// Modify the colour data of each tube
set(h(i),'CData',interp3(x,y,z,vel,get(h(i),'XData')...
,get(h(i),'YData'),get(h(i),'ZData'),'spline'))
end
drawnow
view(3)
axis tight
shading interp;
gives this result
NOTES:
1) I don't know if this is fully correct, I don't know how to test it
2) You have to interpolate the velocity data from the points where it's known onto the vertices of the streamtubes
3) I found the spline interpolation option to work best, but the other options might work better in other cases
Related
If there is an easier way to do this in general any suggestions would be appreciated.
I have imported a .nc file into Matlab and currently have a surface plot created from the interpolated matrix of data which corresponds to longitudes and latitudes. An alpha scale has been applied to add opacity and now I would like to place a map of said longs and lats beneath it so that it acts as an overlay.
here is the code used to plot where xq,yq is the mesh longitude and latitude grid and newMatrix is the interpolated version of the original matrix. Attached is the top view surf plot which I would like a map of long lat restricted x,y axis beneath (line style or topographic)
f = figure;
ax = axes('Parent',f);
h = surf(xq,yq,newMatrix,'Parent',ax);
set(h, 'edgecolor','none');
view(ax,[0,90]);
alpha color
alpha scaled
grid off
colorbar;
I'm aware of geomap but I'm not sure how it can be used in this way without causing the axis to misalign or just not be applied correctly. Before I was using a contour plot but found it easier to interpolate and plot with surf as per this post: Matlab how to make smooth contour plot?
So I have data in the form [x y z intensity] that I plot on a scatter3 figure with xyz axes. The colour of the data is used to dictate the intensity value. Problem is, using a scatter plot means the data points show up as discrete points. What I need, is a smooth shape - so I guess I need some kind of interpolation between the points?
I've tried using trisurf, but the problem with this one is that it interpolates between points that it shouldn't. So where I should have 'gaps' in my surface, it joins up the edges instead so it fills in the gaps. See the attached pics for clarification.
Does anyone have any suggestions?
The code I use is as below (the commented out scatter3 is what does the scatter plot, the rest does the trisurf):
% Read in data
dataM = csvread('3dDispersion.csv');
% scatter3(dataM(:,1), dataM(:,2), dataM(:,3), 5, dataM(:,4),'filled');
% Plot
hold on;
x = dataM(:,1);
y = dataM(:,2);
freq = dataM(:,3);
tri = delaunay(x,y);
h = trisurf(tri, x, y, freq);
% Make it pretty
% view(-45,30);
view(3);
axis vis3d;
lighting phong;
shading interp;
Use the boundary function in Matlab. This will apply a mesh similar to shrinkwrap over your points. In order to reduce the "gap closers", you will want to increase the "shrink factor".
Try K = boundary(X,Y,Z,0.9)
Where X, Y & Z are the vectors of your data points
https://www.mathworks.com/help/matlab/ref/boundary.html
You can then use trimesh or related surface plotting functions depending on how you want to display it.
To state it simply, how do I map a point in the coordinate system used for plotting to figure coordinates in Matlab?
For a more thorough explanation, consider the following dummy code:
figure(1);
axes('position', [0.1 0.1 0.8 0.8]); % define position of axis in fig coords
hold on;
box on;
xlim([0, 2*pi]);
ylim([-1.1, 1.1]);
% plot something
t = 2*pi*linspace(0,1,100);
plot(t, sin(t));
The limits of the axis are [0, 2*pi] and [-1.1, 1.1]. These are the plotting coordinates I refer to. The position of the axis is defined with figure coordinates.
Let's say I want to find out the figure coordinates of a given point, what should I do? For example, the point [pi, 0] should be at the exact center (at [0.5 0.5]). But what' the figure coordinates of, say, [pi/2, 1]?
I could easily write a routine that works in this specific case using the known limits of the axes, and the position of the axes. I am, however, looking for a more general solution. What if my plot uses logarithmic scales? What if it's a 3D plot? Etc. etc. I would imagine Matlab has a simple routine for this but I haven't been able to find it.
Also, is there a routine for the opposite direction, mapping from figure cooridnates to plotting coordinates?
Edit
What I'm trying to achieve, ultimately, is fancy figures. More specifically I want to put annotations at exact points.
I have a figure which consists of different levels of a contour plotted using the hold on function. I want to fill the space between the levels of contour with a color. Could you please assist me how can I do that. I have already tried the contourf function. The figure consists of different red colored levels of a contour, what I want is a solid color filled between these contour levels.
I am not sure if I got exactly what you wanted but here goes a possible solution to your problem.
If you plotted using the hold on function I would therefore assume you have each contour in a different variable. If so you can use logic to check whether a contour is higher or lower relatively to another. If your problem is that you do not have the same x axis for each so that you can use logic just interpolate for each contour (for example between -0.8 and 0.8)
I will give an example of what I am saying. See if this helps.
%simulated contours
x=linspace(0,pi,100);
y = sin(x);
y2 = sin(x)*2;
y3 = sin(x)*3;
figure, hold on,
plot(x,y),
plot(x,y2),
plot(x,y3),
%fill contours
[X,Y]=meshgrid(x,0:3/100:3);
zzz=(Y<repmat(y,size(Y,1),1))+(Y<repmat(y2,size(Y,1),1))+(Y<repmat(y3,size(Y,1),1));
figure,imagesc(zzz)
set(gca,'YDir','normal')
I need to ask help in plotting a 3D volume in MATLAB. My data set includes the X, Y, Z coordinate and corresponding intensity value, V.
I was using pcolor (X,Y,V) and shading interp while i was doing the 2D images but then I got stuck when I am about to create the 3D images. I have tried scatter3, smooth3 and slice but it seems it does not fit the function I need.
My goal is to plot the 3D grid with the corresponding intensity value per coordinate and apply shading interp between these points.
I am really new in 3D plotting and I would really appreciate any help in achieving my goal. Thank you so much!
Here are some example of images that I am trying to create
(source: ndt.net)
(source: www.bam.de)
I have a solution for your first example, in which you show three cross-sections of the volume data. With this solution you can essentially plot several pcolor with different orientations, in one same 3D figure.
First, you need the data for the different slices. This is exactly what you had when you did pcolor(X,Y,V) to plot the cross section in 2D, where X, Y and V are two dimensional matrices. You will also need to create a matrix Z with the z-position of the slice (e.g. Z = zeros(size(X)) + z0). Then you use the command surface(X,Y,Z,V) to plot the cross section image in 3D, where X,Y,Z are the positions, and V is the color (value of the function).
Repeat this procedure for all the other slices, using appropriate X,Y,Z,V matrices for each slice. For slices oriented on other axes you will have to define X,Y,Z accordingly. Remember to use "hold on" after the first surface command, so that all the slices are plotted.
Example:
surface(X1,Y1,Z1,V1); shading interp; hold on
surface(X2,Y2,Z2,V2); shading interp;
surface(X3,Y3,Z3,V3); shading interp;
colormap(jet(2048)); caxis([0,3]); % color axis colormap and scaling
axis equal; xlabel('X'); ylabel('Y'); zlabel('Z') % X,Y,Z scaling and label
Result figure here: