Filled contour plot on other planes (X-Z or Y-Z)

Hello I was looking for a nice way to visualize my 3D data.

Firstly, I did it using slices of pcolor plots in different place.

However, it's hard to interpret values like this

So I was trying to repeat this plot with contourf but it only allows plotting in X-Y plane.

Is any possibility to create filled contours in other planes?

I found only the contourslice function for contours.

Answer 1

[Benjamin Kraus]

contourf works fine when used with an hgtransform, except it is not updating the automatically selected limits correctly, so you will need to update the limits to make sure your rotated contour object is visible in the axes.

I'm not quite sure why you are getting the error "The new value for the Matrix property may cause rendering problems.", but I suspect it has nothing to do with contour, but rather the specific Matrix you are using is not well defined. If you can provide the specific matrix that you used that produced that error message, that would be helpful to get a better idea of why you get that error message.

Considering the example code you provided one of your comments, with some small modifications:

% Default Matrix (eye(4)) works fine, as expected:
fig = figure;
ax = axes('Parent',fig);
t = hgtransform('Parent',ax);
Z = peaks;
contourf(Z,32,':','Parent',t);

% Rotating 90 degrees around X moves the contour into the X/Z plane, and
% requires updating the limits and view.
fig = figure;
ax = axes('Parent',fig);
t = hgtransform('Parent',ax);
Z = peaks;
contourf(Z,32,':','Parent',t);
t.Matrix = makehgtform('xrotate',pi/2);
ylim([-1 1])
zlim([1 49]);
view(0,0)

% The contour starts out at z = 0, x = [1 49], and y = [1 49]. If you
% rotate 45 degrees around the X-axis, the new location is:
% x = [1 49]
% y = sqrt(2)/2.*[1 49]
% z = sqrt(2)/2.*[1 49]
beforeX = [1 49];
beforeY = [1 49];
beforeZ = [0 0];
beforeLim = [beforeX; beforeY; beforeZ; [0 0]];
transformationMatrix = makehgtform('xrotate',pi/4);
afterLim = transformationMatrix*beforeLim;
afterX = afterLim(1,:);
afterY = afterLim(2,:);
afterZ = afterLim(3,:);

fig = figure;
ax = axes('Parent',fig);
t = hgtransform('Parent',ax);
Z = peaks;
contourf(Z,32,':','Parent',t);
t.Matrix = transformationMatrix;
xlim(afterX)
ylim(afterY)
zlim(afterZ)

% The contour starts out at z = 0, x = [1 49], and y = [1 49]. If you
% rotate 2 degrees (pi/90) around the Y-axis ([0 1 0]), the new location is:
% x = ~[1 49]
% y = ~[1 49]
% z = ~[-1.7 -0.03]
beforeX = [1 49];
beforeY = [1 49];
beforeZ = [0 0];
beforeLim = [beforeX; beforeY; beforeZ; [0 0]];
transformationMatrix = makehgtform('axisrotate',[0 1 0],pi/90);
afterLim = transformationMatrix*beforeLim;
afterX = sort(afterLim(1,:));
afterY = sort(afterLim(2,:));
afterZ = sort(afterLim(3,:));

fig = figure;
ax = axes('Parent',fig);
t = hgtransform('Parent',ax);
Z = peaks;
contourf(Z,32,':','Parent',t);
t.Matrix = transformationMatrix;
xlim(afterX)
ylim(afterY)
zlim(afterZ)

% Note that makehgtform('axisrotate',[0 1 0],pi/90) is equivalent to
% makehgtform('yrotate',pi/90), so you will get the same answer.
mat1 = makehgtform('axisrotate',[0 1 0],pi/90)

mat1 = 4×4

0.9994 0 0.0349 0 0 1.0000 0 0 -0.0349 0 0.9994 0 0 0 0 1.0000

mat2 = makehgtform('yrotate',pi/90)

mat2 = 4×4

0.9994 0 0.0349 0 0 1.0000 0 0 -0.0349 0 0.9994 0 0 0 0 1.0000

isequal(mat1, mat2)

ans = logical
   1

[Volodymyr Rodin]

Thanks a lot for your answer, it makes sense and I hope in the next release it will be easier to do this.

I had obtained these warning messages when I was changing matrix in Property Inspector. It actually doesn;t allow to totally change matrix in one go but only one number per edit.

So I went from [100;010;001] to [100;011;001] to [100;011;0-11] then to [100;001;0-10] bu removing extra 1-s

[Walter Roberson]

Ah, I did try

xlim auto
ylim auto
zlim auto

but I guess the "auto" it computed was based on the un-transformed coordinates. When I manually change the limits, I can see the contourf created in https://www.mathworks.com/matlabcentral/answers/1910215-filled-contour-plot-on-other-planes-x-z-or-y-z#comment_2609440

[Benjamin Kraus]

@Walter Roberson: That is exactly the issue, the "auto" limits are being (incorrectly) calculated based on the untransformed coordinates.

[Volodymyr Rodin]

@Benjamin Kraus, But is it possible to put three contourf plots at different angles on the same figure and axis with method that you described?

Edit: Possible

[Walter Roberson]

You would have to calculate the bounds from each transform matrix and then take min and max of each dimension. Or just wing it based on what you know about the sizes.

[Volodymyr Rodin]

@Walter Roberson yep, I got it. It's a bit strange that contours are visible in front

[Walter Roberson]

I suspect that you can change the FaceAlpha to make the fill area more transparent if you want.

[Benjamin Kraus]

@Walter Roberson is correct, but note that FaceAlpha was added to contour in R2022b.

[Volodymyr Rodin]

@Benjamin Kraus the issue is that plots are transparent to each other even with FaceAlpha=1

With activated selection it becomes really visible. And edges of contours from 3 planes are visible all time

[Volodymyr Rodin]

@Benjamin Kraus Putting FaceAlpha to 0.99 for one plane fixes this bug (at 0.999 it still exists), that's odd

[Benjamin Kraus]

@Volodymyr Rodin that is indeed strange, and looks like it could be a bug (particularly the fact that setting FaceAlpha to 0.999 makes a difference). Can you share the code you used to reproduce those images? I'll take a look and create a bug report if needed.

[Volodymyr Rodin]

@Benjamin Kraus Here is an example with peaks

figure1 = figure(1);
axes1 = axes('Parent',figure1);
hold(axes1,'on');

Z=peaks(49);

[~,ix]=contourf(Z,32,':','Parent',axes1)

ix = 
  Contour with properties:

    EdgeColor: [0 0 0]
    LineStyle: ':'
    LineWidth: 0.5000
    FaceColor: 'flat'
    LevelList: [-6.5466 -6.1036 -5.6605 -5.2174 -4.7743 -4.3312 -3.8881 -3.4450 -3.0020 -2.5589 -2.1158 -1.6727 -1.2296 -0.7865 -0.3434 0.0996 0.5427 0.9858 1.4289 1.8720 2.3151 2.7581 3.2012 3.6443 4.0874 4.5305 4.9736 5.4167 5.8597 6.3028 6.7459 … ]
        XData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        YData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        ZData: [49×49 double]

  Show all properties

ix.ZLocation=7;

xlim([0 49])
ylim([0 49])
zlim([0 49])

set(axes1,'ColorScale','linear','ZMinorTick','on','ZScale','linear');
view(axes1,[50 40]);
axis('square')

t = hgtransform('Parent',axes1);

[~,ix2]=contourf(Z,32,':','Parent',t )

ix2 = 
  Contour with properties:

    EdgeColor: [0 0 0]
    LineStyle: ':'
    LineWidth: 0.5000
    FaceColor: 'flat'
    LevelList: [-6.5466 -6.1036 -5.6605 -5.2174 -4.7743 -4.3312 -3.8881 -3.4450 -3.0020 -2.5589 -2.1158 -1.6727 -1.2296 -0.7865 -0.3434 0.0996 0.5427 0.9858 1.4289 1.8720 2.3151 2.7581 3.2012 3.6443 4.0874 4.5305 4.9736 5.4167 5.8597 6.3028 6.7459 … ]
        XData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        YData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        ZData: [49×49 double]

  Show all properties

ix2.ZLocation=9;
t.Matrix=makehgtform('yrotate',-pi/2)*makehgtform('translate',[0 0 -18]);


t2 = hgtransform('Parent',axes1);

[~,ix3]=contourf(Z,32,':','Parent',t2)

ix3 = 
  Contour with properties:

    EdgeColor: [0 0 0]
    LineStyle: ':'
    LineWidth: 0.5000
    FaceColor: 'flat'
    LevelList: [-6.5466 -6.1036 -5.6605 -5.2174 -4.7743 -4.3312 -3.8881 -3.4450 -3.0020 -2.5589 -2.1158 -1.6727 -1.2296 -0.7865 -0.3434 0.0996 0.5427 0.9858 1.4289 1.8720 2.3151 2.7581 3.2012 3.6443 4.0874 4.5305 4.9736 5.4167 5.8597 6.3028 6.7459 … ]
        XData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        YData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        ZData: [49×49 double]

  Show all properties

ix3.ZLocation=27;
t2.Matrix=makehgtform('xrotate',pi/2)*makehgtform('translate',[0 0 -27*2]);

% ix3.FaceAlpha=0.99

[Benjamin Kraus]

Thanks. This does seem to be a bug. I've reported the bug to the developers. In the meantime, if setting FaceAlpha to 0.99 works, I would continue doing that.

If I had to guess, when you set FaceAlpha to anything close to 1, there is an optimization that is being done for performance reasons that skips some transparency calculations, and the bug is in that pathway. When you set the FaceAlpha to <0.99, it will likely take longer to render, because it is doing extra transparency calculations, but it results in a more accurate picture.

Answer 2

[Walter Roberson]

Create a hgtransform() and parent it to the axes. Extract a 2d slice of the volume (interpn() or even just array access and squeeze()) and contoutf() that, parenting it to the hgtransform (pass in the transform handle where you would pass in an axes). Now set the Matrix property of the transform to rotate it to the desired plane. makehgtform is very useful for creating the matrix.

Note that the rightmost transform in makehgtform is one executed first.

[Volodymyr Rodin]

I have tried that as well, but it didn''t work

Here is my code

figure1 = figure(1);
axes1 = axes('Parent',figure1);
set(axes1,'ColorScale','linear','ZScale','linear');
view(axes1,[-45 45]);
axis('square')

t = hgtransform('Parent',axes1);
Rz = makehgtform('xrotate',pi/2);
set(t,'Matrix',Rz);
.....
[~,ix]=contourf(X,Y,Z,32,':','Parent',t)

It simply disappears if Parent object is t and not axes1

Can you provide some example with contourf?

[Volodymyr Rodin]

But this works quite well for hgtransform() example provided in Matlab, that's probably something specific to contourf plot

Edit: It also works for pcolor plot with extra update of Parent after rotation

[Walter Roberson]

your sample does not define t

[Volodymyr Rodin]

Yes, there was this line, I forgot to paste it

t = hgtransform('Parent',axes1);

[Volodymyr Rodin]

Hi, here is the simple example with peaks. And there is something goes really stramge, you can compare it with the commented part

figure1 = figure(1);
% Create axes
axes1 = axes('Parent',figure1);
hold(axes1,'on');
view(axes1,[-45 45]);
t = hgtransform('Parent',axes1);

Works = eye(4);
Fails1 = makehgtform('xrotate',pi/2);
Fails2 = makehgtform('xrotate',pi/4);
Fails3 = makehgtform('axisrotate',[0 1 0],pi/90); %doing strange rotation
Fails4 = makehgtform('yrotate',pi/90); %doing strange rotation

Z = peaks;

[~,ix]=contourf(Z,32,':','Parent',t)

ix = 
  Contour with properties:

    EdgeColor: [0 0 0]
    LineStyle: ':'
    LineWidth: 0.5000
    FaceColor: 'flat'
    LevelList: [-6.5466 -6.1036 -5.6605 -5.2174 -4.7743 -4.3312 -3.8881 -3.4450 -3.0020 -2.5589 -2.1158 -1.6727 -1.2296 -0.7865 -0.3434 0.0996 0.5427 0.9858 1.4289 1.8720 2.3151 2.7581 3.2012 3.6443 4.0874 4.5305 4.9736 5.4167 5.8597 6.3028 6.7459 … ]
        XData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        YData: [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49]
        ZData: [49×49 double]

  Show all properties

% ix=pcolor(Z,'Parent',t)
set(t,'Matrix',Fails1);

% set(ix,'Parent',t)

[Walter Roberson]

Hmmm, I do not know why that is happening.