Volume Properties

Display volume in 3-D viewer

Since R2022b

Volume properties control the appearance and behavior of a Volume object. By changing property values, you can modify certain aspects of the volume. Create a Volume object using the volshow function.

Use dot notation to query and set properties. For example, these commands show how to create a Volume object that displays 3-D volumetric data V, query the value of the Colormap property, and set the value of the Colormap property, respectively.

vol = volshow(V);
cmap = vol.Colormap;
vol.Colormap = parula;

Parent/Child

Parent — Parent

Viewer object

Parent of the Volume object, specified as a Viewer object. You can create a Viewer object using the viewer3d function. A Volume object cannot be reparented.

Data Display

Data — Volumetric data

m-by-n-by-p numeric array | m-by-n-by-p-by-3 numeric array

Volumetric data displayed in the viewer, specified as one of these options:

• An m-by-n-by-p numeric array with non-singleton dimensions.

• An m-by-n-by-p-by-3 numeric array with non-singleton dimensions.

DisplayRange — Display range

2-element row vector | 3-by-2 numeric matrix

Display range used to map voxel values to the colormap and transparency map, specified as one of these options:

• 2-element row vector of the form [min max] — Scale data according to the values min and max. For RGB volumes, specifying a 2-element row vector applies the same data limits to all color channels.

• 3-by-2 numeric matrix with each row of the form [min max] — Scale each RGB channel according to the values min and max in the corresponding row. The first, second, and third rows specify the data limits for the red, green, and blue color channels, respectively.

If you do not specify a DisplayRange property value, by default, the function automatically scales the data based on the DisplayRangeMode property value. If you specify the DisplayRange property value, the DisplayRangeMode property value changes to "manual".

DisplayRangeMode — Display range mode

"data-range" (default) | "type-range" | "10-bit" | "12-bit" | "manual"

Display range mode, specified as one of the options in the table.

Value	Description
"type-range"	Set the display range equal to the data type range. For example, for uint8 images, the display range is [0, 255].
"data-range"	Set the display range equal to the data range of the volume. For RGB volumes, the data range is the overall minimum and maximum across channels. For example, given an RGB volume in which the minimum and maximum values of the R, G, and B channels are [2, 160], [5, 200], and [0, 140], respectively, the display range is [0, 200].
"10-bit"	Set the display range to [0, 1023]. This value is useful for displaying medical images with 10-bit data ranges.
"12-bit"	Set the display range to [0, 4095]. This value is useful for displaying medical images with 12-bit data ranges.
"manual"	Manually set a fixed display range using the DisplayRange property. Specifying the DisplayRange automatically sets the DisplayRangeMode property value to "manual".

Alphamap — Transparency map for volume content

linspace(0,1,256)' (default) | n-element column vector | "linear" | "quadratic" | "cubic"

Transparency map for the volume, specified as one of the values in the table.

The DisplayRange property determines how values of Data map to the transparency map. Values less than or equal to the minimum of the DisplayRange map to the first value of the transparency range, and all values greater than or equal to the maximum of the DisplayRange map to the last value of the transparency range.

When the AlphaData property is nonempty, the Alphamap property has no effect.

Value	Description
n-element column vector with values in the range [0, 1]	Values in Data map linearly to the transparency values in Alphamap.
"linear" (since R2024b)	Values in Data map linearly to transparencies in the range [0, 1].
"quadratic" (since R2024b)	Values in Data map quadratically to transparencies in the range [0, 1]. Use this option to apply a more rapid change in transparency between low and high values of Data compared to "linear".
"cubic" (since R2024b)	Values in Data map cubically to transparencies in the range [0, 1]. Use this option to apply the most rapid change in transparency between low and high values of Data.

AlphaData — Transparency channel

[] (default) | m-by-n-by-p array

Transparency channel for the volume, specified as an empty vector ([]) or an m-by-n-by-p array that matches the size of the first three dimensions of the volume.

• When AlphaData is empty, the transparency of each voxel is controlled by the intensity or luminance of the voxel according to the Alphamap property.

• When AlphaData is nonempty, the transparency of each voxel is controlled by the corresponding element in AlphaData.

Colormap — Colormap

gray(256) (default) | n-by-3 numeric matrix

Colormap of grayscale volume content, specified as an n-by-3 numeric matrix with values in the range [0, 1]. The maximum number of colors n is 256. You can specify the colormap as a numeric matrix directly, or as the name of predefined colormap such as turbo or parula. For a complete list of colormaps, see Colormaps. This property has no effect when viewing RGB volumes.

Visible — Object is visible

"on" (default) | on/off logical value

Object is visible in the 3-D scene, specified as "on" or "off", or as a numeric or logical 1 (true) or 0 (false). A value of "on" is equivalent to true, and "off" is equivalent to false. The value is stored as an on/off logical value of type OnOffSwitchState.

Transformation — Transformation applied to volume

affinetform3d object | rigidtform3d object | simtform3d object | transltform3d object

Transformation applied to the volume in the 3-D scene, specified as an affinetform3d, rigidtform3d, simtform3d, or transltform3d object. Use the Transformation property to increase the size of the volume, rotate the volume, or perform other affine transformations. The default value is an affinetform3d object that performs an identity transformation.

ClippingPlanes — Clipping planes

[] (default) | N-by-4 matrix

Clipping planes applied locally to the object, specified as an N-by-4 matrix where each row corresponds to the equation for a clipping plane. The maximum number of clipping planes, N, is six. Each clipping plane is specified as a 1-by-4 vector, in world coordinates, following the Hessian normal form where the first three values represent the plane's normal vector and the fourth value is the signed distance from the origin to the plane.

Volume Rendering

RenderingStyle — Rendering style

"VolumeRendering" (default) | "CinematicRendering" | "LightScattering" | "MaximumIntensityProjection" | "MinimumIntensityProjection" | "GradientOpacity" | "Isosurface" | "SlicePlanes"

Rendering style, specified as one of the values in the table.

Value	Description
"VolumeRendering"	View the volume based on the specified color and transparency for each voxel.
"CinematicRendering"	View the volume based on the specified color and transparency for each voxel, with iterative postprocessing that produces photorealistic shadows and lighting. This rendering style is useful for displaying opaque volumes.
"LightScattering"	View the volume using a volumetric light scattering model that simulates the absorption, inscattering, and outscattering of light through the volume. This rendering style is useful for displaying translucent volumes that do not have large intensity gradients, such as smoke, fog, and clouds.
"MaximumIntensityProjection"	View the voxel with the highest intensity value for each ray projected through the data. For RGB volumes, the luminance of the voxel in CIE 1976 L*a*b* color space.
"MinimumIntensityProjection"	View the voxel with the lowest intensity value for each ray projected through the data. For RGB volumes, the luminance of the voxel in CIE 1976 L*a*b* color space.
"GradientOpacity"	View the volume based on the specified color and transparency with an additional transparency applied if the voxel is similar in intensity (grayscale volumes) or luminance (RGB volumes) to the previous voxel along the viewing ray. When a volume with uniform intensity is rendered using "GradientOpacity", the internal portion of the volume appears more transparent than the "VolumeRendering" rendering style, enabling better visualization of the intensity or luminance gradients in the volume.
"Isosurface"	View an isosurface of the volume specified by the value in IsosurfaceValue.
"SlicePlanes"	View three orthogonal slice planes.

CinematicNumIterations — Number of iterations

positive integer scalar

Number of iterations, specified as a positive integer scalar. This property affects the visualization only when the RenderingStyle property value is "CinematicRendering". The default number of iterations is 100 for systems with hardware graphics rendering. This value is sufficient for most volumes and lighting scenarios. Decreasing the number of iterations increases rendering speed, but can decrease rendering quality.

If your system does not support hardware graphics rendering, the default number of iterations is 20. For details about graphics rendering in MATLAB^®, see System Requirements for Graphics.

LightScatteringQuality — Light scattering quality

"auto" (default) | numeric scalar

Light scattering quality, specified as "auto" or a numeric scalar in the range [0, 1]. This property affects the visualization only when the RenderingStyle property value is "LightScattering". A larger quality value generates a more realistic rendering, but requires longer rendering times. By default, the quality value adjusts automatically to manage performance during interactions such as pan and zoom.

IsosurfaceValue — Isosurface value

0.15 (default) | numeric scalar

Isosurface value, specified as a numeric scalar in the range [0, 1]. This property affects the visualization only when the RenderingStyle property value is "Isosurface".

SlicePlaneValues — Orthogonal or oblique slice planes

N-by-4 matrix

Orthogonal or oblique slice planes of the volume, specified as an N-by-4 matrix where each row corresponds to the equation for a slice plane. The maximum number of slice planes, N, in SlicePlaneValues is six. The slice planes are visible only when the RenderingStyle property is "SlicePlanes". The default value is three orthogonal planes that slice through the center of the volume. Each slice plane is specified as a 1-by-4 vector in voxel coordinates following the Hessian normal form where the first three values represent the normal vector of the plane and the fourth value is the signed distance from the origin to the plane.

GradientOpacityValue — Gradient opacity value

0.3 (default) | numeric scalar

Gradient opacity value, specified as a numeric scalar in the range [0, 1]. When set to 0, no gradient opacity is applied. When set to 1, the maximum amount of gradient opacity is applied. This property affects the visualization when the RenderingStyle property value is "GradientOpacity" or the OverlayRenderingStyle property value is "GradientOverlay".

SpecularReflectance — Specular reflectance

0.4 (default) | numeric scalar

Specular reflectance, specified as a numeric scalar in the range [0, 1]. This value controls the amount of light reflected by the volume. Increase the reflectance to make the volume appear shinier.

Overlay

OverlayData — Overlay data

numeric array

Overlay data to be blended with the object data during rendering, specified as a numeric array. The object shows the overlay only when the RenderingStyle property value is "SlicePlanes", "VolumeRendering", or "GradientOpacity". You can modify the appearance of the overlay by changing the OverlayDisplayRange, OverlayRenderingStyle, OverlayColormap, and OverlayAlphamap properties.

OverlayDisplayRange — Overlay display range

[0, 255] (default) | 2-element numeric vector

Overlay display range, specified as a 2-element numeric vector of the form [low high] that specifies the minimum and maximum of the display range. If you specify this property directly, the OverlayDisplayRangeMode property value automatically changes to "manual". When the OverlayDisplayRangeMode property value is "data-range" or "type-range", this property automatically updates to reflect the current display range.

OverlayDisplayRangeMode — Overlay display range mode

"8-bit" (default) | "type-range" | "data-range" | "manual"

Overlay display range mode, specified as one of the options in the table.

Value	Description
"8-bit"	Set the overlay display range to [0 255].
"type-range"	Set the overlay display range equal to the data type range for OverlayData. For example, if OverlayData is of data type double, the display range is [0 1].
"data-range"	Set the display range equal to the data range of OverlayData.
"manual"	Manually set a fixed display range using the OverlayDisplayRange property. Specifying the OverlayDisplayRange property automatically sets the OverlayDisplayRangeMode to "manual".

OverlayColormap — Overlay colormap

n-by-3 numeric matrix

Overlay colormap, specified as an n-by-3 numeric matrix with values in the range [0, 1]. The maximum number of colors n is 256. You can specify the colormap as a numeric matrix directly, or as the name of predefined colormap such as turbo or parula. For a complete list of colormaps, see Colormaps.

This property affects the visualization only when the OverlayData property is nonempty. The default colormap maximizes color differences between adjacent colors in the colormap, which helps visually distinguish between different values in a discrete label image. When displaying continuous overlay data as a heatmap, consider specifying a predefined colormap with gradual color changes, such as turbo or parula.

The OverlayDisplayRange property determines how values of OverlayData map to the colormap. Values less than or equal to the minimum of the OverlayDisplayRange map to the first color in OverlayColormap, and all values greater than or equal to the maximum of the OverlayDisplayRange map to the last color in OverlayColormap.

OverlayAlpha — Uniform transparency value for overlay

0.2 (default) | numeric scalar | []

Uniform transparency value for the overlay image, specified as a numeric scalar in the range [0, 1] or an empty array. Specify a numeric scalar to apply a uniform transparency to all nonzero pixels in OverlayData. Zero-valued pixels display fully transparent.

To specify a nonuniform transparency, or to apply a uniform transparency to all pixels including zero-valued pixels, specify the OverlayAlphamap property. If you specify OverlayAlphamap, then this property automatically changes to an empty matrix, [].

OverlayAlphamap — Nonuniform transparency map for overlay

n-element column vector | "linear" | "quadratic" | "cubic"

Nonuniform transparency map for the overlay image, specified as one of the values in the table. Specify this property to apply a nonuniform transparency to pixels in OverlayData. By default, OverlayAlphamap is a 256-element column vector that reflects the current OverlayAlpha value.

The OverlayDisplayRange property determines how values of OverlayData map to the transparency range. Values less than or equal to the minimum of the OverlayDisplayRange map to the first value of the transparency range, and all values greater than or equal to the maximum of the OverlayDisplayRange map to the last value of the transparency range.

Value	Description
n-element column vector with values in the range [0, 1]	Values in OverlayData map linearly to the transparency values in OverlayAlphamap.
"linear" (since R2024b)	Values in OverlayData map linearly to transparencies in the range [0, 1].
"quadratic" (since R2024b)	Values in OverlayData map quadratically to transparencies in the range [0, 1]. Use this option to apply a more rapid change in transparency between low and high values of OverlayData compared to "linear".
"cubic" (since R2024b)	Values in OverlayData map cubically to transparencies in the range [0, 1]. Use this option to apply the most rapid change in transparency between low and high values of OverlayData.

OverlayRenderingStyle — Overlay rendering style

"LabelOverlay" (default) | "VolumeOverlay" | "GradientOverlay"

Overlay rendering style, specified as one of the values in the table.

Value	Description
"LabelOverlay"	View the overlay based on the color and transparency of each labeled region. Use this rendering style to visualize ordinal data like binary or semantic segmentation results on top of your data.
"VolumeOverlay"	View the overlay based on the specified color and transparency for each voxel.
"GradientOverlay"	View the overlay based on the color and transparency for each voxel with an additional transparency applied based on the difference between the voxel and the previous voxel along the viewing ray.

Version History

Introduced in R2022b

R2024b: Specify volume display range and transparency map

• Control the display range used to scale the volume by using the new DisplayRange and DisplayRangeMode properties.

• Control the display range used to scale the volume overlay by using the new OverlayDisplayRange and OverlayDisplayRangeMode properties.

• Specify a uniform transparency for all nonzero label values while hiding background labels by using the new OverlayAlpha property.

• For easier specification of transparency maps, the new options "linear", "quadratic", and "cubic" have been added for the Alphamap and OverlayAlphamap properties.

R2024b: New default colormap, OverlayThreshold not recommended

• To improve support for labeling workflows, the default OverlayColormap property value has changed from turbo(256) to a custom colormap that maximizes differences between adjacent colors. To apply the same colormap as in previous releases, specify the Colormap property as turbo(256).

• To apply a uniform transparency while hiding background labels, the new OverlayAlpha property is recommended over the OverlayThreshold property. There are no plans to remove support for existing instances of OverlayThreshold.

R2023b: Cinematic rendering, volumetric light scattering, and specular reflectance

• Specify the RenderingStyle property as "CinematicRendering" to display a photorealistic volume using iterative postprocessing. Specify the number of postprocessing iterations using the new CinematicNumIterations property.

• Specify the RenderingStyle property as "LightScattering" to display the volume with volumetric light scattering, including light absorption, inscattering, and outscattering. Specify the balance between rendering quality and speed using the new LightScatteringQuality property.

• Control the amount of light reflected by a volume using the new SpecularReflectance property. Increase the specular reflectance to make a volume appear shinier.