volshow

Display volume

Description

A volshow object displays volume and enables you to modify the appearance of the display.

Creation

Syntax

volshow(V)

volshow(V,config)

volshow(V,Name,Value)

vs = volshow(___)

Description

volshow(V) displays 3-D grayscale volume V in a figure. You can rotate and zoom in and out on the display interactively using the mouse.

volshow(V,config) displays the 3-D grayscale volume V. config is a struct exported from the Volume Viewer app. The config struct controls visualization of the volume, containing values for volshow object properties.

volshow(V,Name,Value) displays the volume, using one or more name-value pairs to set properties that control the visualization of the volume. For a list of name-value pairs, see Properties. Enclose each property name in quotes.

Example: volshow(V,'BackgroundColor','w') displays 3-D grayscale volume V in a figure with a white background color.

vs = volshow(___) returns a volshow object with properties that can be used to control visualization of the volume.

Input Arguments

V — 3-D grayscale volume

numeric array

3-D grayscale volume, specified as a numeric array.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | logical

config — Rendering information exported by Volume Viewer

struct

Rendering information exported by Volume Viewer, specified as a struct.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | logical

Properties

Alphamap — Transparency map for volume content

256-by-1 numeric vector

Transparency map for the volume content, specified as a 256-by-1 numeric array, with values in the range [0, 1]. The default transparency map is the vector linspace(0,1,256)'.

BackgroundColor — Background color

[0.3 0.75 0.93] (default) | RGB triplet | color name | short color name

Background color, specified as an RGB triplet, a color name, or a short color name.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0,1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet	Appearance
'red'	'r'	[1 0 0]
'green'	'g'	[0 1 0]
'blue'	'b'	[0 0 1]
'cyan'	'c'	[0 1 1]
'magenta'	'm'	[1 0 1]
'yellow'	'y'	[1 1 0]
'black'	'k'	[0 0 0]
'white'	'w'	[1 1 1]

Here are the RGB triplets for the default colors that MATLAB^® uses in many types of plots.

RGB Triplet	Appearance
[0 0.4470 0.7410]
[0.8500 0.3250 0.0980]
[0.9290 0.6940 0.1250]
[0.4940 0.1840 0.5560]
[0.4660 0.6740 0.1880]
[0.3010 0.7450 0.9330]
[0.6350 0.0780 0.1840]

Example: 'BackgroundColor','r'

Example: 'BackgroundColor','green'

Example: 'BackgroundColor',[0 0.4470 0.7410]

CameraPosition — Location of camera

[4 4 2.5] (default) | 3-element vector

Location of camera, or the viewpoint, specified as a 3-element vector of the form [x y z]. This vector defines the axes coordinates of the camera location, which is the point from which you view the axes. The camera is oriented along the view axis, which is a straight line that connects the camera position and the camera target. Changing the CameraPosition property changes the point from which you view the volume. For an illustration, see Camera Graphics Terminology. Interactively rotating the volume modifies the value of this property.

CameraTarget — Point used as camera target

[0 0 0] (default) | 3-element vector

Point used as camera target, specified as a 3-element vector of the form [x y z]. The camera is oriented along the view axis, which is a straight line that connects the camera position and the camera target. For an illustration, see Camera Graphics Terminology.

CameraUpVector — Vector defining upwards direction

[0 0 1] (default) | 3-element vector

Vector defining upwards direction, specified as a 3-element direction vector of the form [x y z]. By default, volshow defines the z-axis as the up direction ([0 0 1]). For an illustration, see Camera Graphics Terminology. Interactively rotating the volume modifies the value of this property.

CameraViewAngle — Field of view

15 (default) | numeric scalar

Field of view, specified as a scalar angle in the range [0, 180). The larger the angle, the larger the field of view. Also, as the angle increases, objects appear smaller in the scene. For an illustration, see Camera Graphics Terminology.

Colormap — Colormap of volume content

gray(256) (default) | 256-by-3 numeric array

Colormap of the volume content, specified as a 256-by-3 numeric array with values in the range [0, 1].

InteractionsEnabled — Interactivity of volume

true (default) | false

Interactivity of the volume, specified as true or false. When true, you can zoom using the mouse scroll wheel, and rotate by clicking and dragging on the volume. Rotation and zoom are performed about the value specified by the CameraTarget property. When false, you cannot interact with the volume.

IsosurfaceColor — Isosurface color

RGB triplet | color name | short color name

Isosurface color, specified as an RGB triplet, a color name, or a short color name. This property specifies the volume color when the Renderer property is set to 'Isosurface'.

You can specify any color using an RGB triplet. An RGB triplet is a 3-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range [0,1].

You can specify some common colors by name as a string scalar or character vector. This table lists the named color options and the equivalent RGB triplets.

Color Name	Short Name	RGB Triplet	Appearance
'red'	'r'	[1 0 0]
'green'	'g'	[0 1 0]
'blue'	'b'	[0 0 1]
'cyan'	'c'	[0 1 1]
'magenta'	'm'	[1 0 1]
'yellow'	'y'	[1 1 0]
'black'	'k'	[0 0 0]
'white'	'w'	[1 1 1]

Here are the RGB triplets for the default colors that MATLAB uses in many types of plots.

RGB Triplet	Appearance
[0 0.4470 0.7410]
[0.8500 0.3250 0.0980]
[0.9290 0.6940 0.1250]
[0.4940 0.1840 0.5560]
[0.4660 0.6740 0.1880]
[0.3010 0.7450 0.9330]
[0.6350 0.0780 0.1840]

Example: 'IsosurfaceColor','r'

Example: 'IsosurfaceColor','green'

Example: 'IsosurfaceColor',[0 0.4470 0.7410]

Isovalue — Value that defines volume surface

0.49 (default) | nonnegative number

Value that defines the volume surface drawn when the Renderer property is set to 'Isosurface', specified as a nonnegative number in the range [0, 1].

Lighting — Include light source in rendering

true (default) | false

Include light source in rendering, specified as a logical scalar.

Parent — Parent of volshow object

gcf (default) | uipanel | figure

Parent of the volshow object, specified as a handle to a uipanel or figure. If you do not specify a parent, then the parent of the volshow object is gcf.

Renderer — Rendering style

'VolumeRendering' | 'MaximumIntensityProjection' | 'Isosurface'

Rendering style, specified as one of the values in this table. When the volume is logical, the default rendering style is 'Isosurface', otherwise the default rendering style is 'VolumeRendering'.

Value	Description
'VolumeRendering'	View the volume based on the specified color and transparency for each voxel.
'MaximumIntensityProjection'	View the voxel with the highest intensity value for each ray projected through the data.
'Isosurface'	View an isosurface of the volume specified by the value in Isovalue.

ScaleFactors — Scale factors used to rescale volume

[1 1 1] (default) | 1-by-3 positive numeric array

Scale factors used to rescale volume, specified as a 1-by-3 positive numeric array. The values in the array correspond to the scale factor applied in the x, y, and z direction.

Object Functions

setVolume

Set new volume

Examples

Create Animated GIF of Spiral Volume

Load and view the volume.

load('spiralVol.mat');
h = volshow(spiralVol);

Specify the name of the GIF file.

filename = 'animatedSpiral.gif';

Create an array of camera positions around the unit circle.

vec = linspace(0,2*pi(),120)';
myPosition = [cos(vec) sin(vec) ones(size(vec))];

Loop through and create an image at each camera position.

for idx = 1:120
    % Update current view.
    h.CameraPosition = myPosition(idx,:);
    % Use getframe to capture image.
    I = getframe(gcf);
    [indI,cm] = rgb2ind(I.cdata,256);
    % Write frame to the GIF File.
    if idx == 1
        imwrite(indI, cm, filename, 'gif', 'Loopcount', inf, 'DelayTime', 0.05);
    else
        imwrite(indI, cm, filename, 'gif', 'WriteMode', 'append', 'DelayTime', 0.05);
    end
end

Visualize Volume of MRI Data

Load MRI data and remove the singleton dimension.

load mri
V = squeeze(D);

Generate a colormap and transparency (alpha) map suited for MRI images.

intensity = [0 20 40 120 220 1024];
alpha = [0 0 0.15 0.3 0.38 0.5];
color = ([0 0 0; 43 0 0; 103 37 20; 199 155 97; 216 213 201; 255 255 255]) ./ 255;
queryPoints = linspace(min(intensity),max(intensity),256);
alphamap = interp1(intensity,alpha,queryPoints)';
colormap = interp1(intensity,color,queryPoints);

View the volume with the custom colormap and transparency map. Click and drag the mouse to rotate the volume. Use the scroll wheel to zoom in and out of the volume.

vol = volshow(V,'Colormap',colormap,'Alphamap',alphamap);

Visualize Volume of CT Data

This example uses 3-D volumetric human chest CT scan data. To run this example, you must download the sample data from MathWorks™ using the Add-On Explorer. See Install Sample Data Using Add-On Explorer.

Load the data into the workspace.

load chestVolume

Create a colormap and transparency map suited for CT images.

intensity = [-3024,-16.45,641.38,3071];
alpha = [0, 0, 0.72, 0.72];
color = ([0 0 0; 186 65 77; 231 208 141; 255 255 255]) ./ 255;
queryPoints = linspace(min(intensity),max(intensity),256);
alphamap = interp1(intensity,alpha,queryPoints)';
colormap = interp1(intensity,color,queryPoints);

View the volume with the custom colormap and transparency map. Click and drag the mouse to rotate the volume. Use the scroll wheel to zoom in and out of the volume.

vol = volshow(V,'Colormap',colormap,'Alphamap',alphamap);

Programatically change the camera position to see a different view of the volume.

vol.CameraPosition = [-1.0533 -0.0093, 0.1593];

Tips

• The volshow function creates a uipanel object in the specified parent figure. Panels are containers that group UI components together. volshow displays volumetric data in the uipanel. In contrast, imshow displays images in an Axes. If you call imshow to display an image in a figure in which volshow has displayed a volume, then imshow does not overwrite the volume displayed by volshow. The Axes created by imshow displays behind the uipanel.

Version History

Introduced in R2018b