Volume

Source (.js)Source (.d.ts)

Introduction

vtk-js includes support for volume rendering using hardware GPU acceleration. The capabilities may change over time but as of this writing it includes support for :

• multi-component data
• at least 24 bits linear resolution
• support for all native data types, 16 bit, float, etc
• opacity transfer functions
• color transfer functions
• volume interpolation of nearest, fast linear and linear
• automatic intermixing of opaque surfaces with volumes

Using volume rendering in vtk-js is very much like using it VTK is you are familiar with VTK. The main objects are :

• RenderWindow/Renderer as usual
• Volume - similar to Actor, holds the property and mapper
• VolumeMapper - takes an ImageData as input
• VolumeProperty - holds the opacity and color transfer functions
• PiecewiseFunction - a piecewise interpolated function, good for opacity transfer functions
• ColorTransferFunction - similar to PiecewiseFunction but support an RGB value at each point.

Usage

// Load the rendering pieces we want to use (for both WebGL and WebGPU)
import 'vtk.js/Sources/Rendering/Profiles/Volume';

import vtkColorTransferFunction from '@kitware/vtk.js/Rendering/Core/ColorTransferFunction';
import vtkHttpDataSetReader from '@kitware/vtk.js/IO/Core/HttpDataSetReader';

import vtkVolume from '@kitware/vtk.js/Rendering/Core/Volume';
import vtkVolumeMapper from '@kitware/vtk.js/Rendering/Core/VolumeMapper';

const vol = vtkVolume.newInstance();
const mapper = vtkVolumeMapper.newInstance();
mapper.setSampleDistance(2.0);
vol.setMapper(mapper);

const reader = vtkHttpDataSetReader.newInstance({ fetchGzip: true });
reader.setUrl(`${__BASE_PATH__}/Data/volume/headsq.vti`).then(() => {
  reader.loadData().then(() => {
    // we wait until the data is loaded before adding
    // the volume to the renderer
    renderer.addVolume(actor);
    renderer.resetCamera();
    renderWindow.render();
  });
});

// create color and opacity transfer functions
const ctfun = vtkColorTransferFunction.newInstance();
ctfun.addRGBPoint(200.0, 1.0, 1.0, 1.0);
ctfun.addRGBPoint(2000.0, 0.0, 0.0, 0.0);

const ofun = vtkPiecewiseFunction.newInstance();
ofun.addPoint(200.0, 0.0);
ofun.addPoint(1200.0, 0.2);
ofun.addPoint(4000.0, 0.4);

vol.getProperty().setRGBTransferFunction(0, ctfun);
vol.getProperty().setScalarOpacity(0, ofun);
vol.getProperty().setScalarOpacityUnitDistance(0, 4.5);
vol.getProperty().setInterpolationTypeToFastLinear();

mapper.setInputConnection(reader.getOutputPort());

See Also

vtkColorTransferFunction vtkImageData vtkPiecewiseFunction vtkVolumeMapper vtkVolumeProperty

Methods

extend

Method use to decorate a given object (publicAPI+model) with vtkVolume characteristics.

Argument	Type	Required	Description
publicAPI		Yes	object on which methods will be bounds (public)
model		Yes	object on which data structure will be bounds (protected)
initialValues	IVolumeInitialValues	No	(default: {})

getMTime

Get the Modified Time which is a monotonic increasing integer global for all vtkObjects.

This allow to solve a question such as:

• Is that object created/modified after another one?
• Do I need to re-execute this filter, or not? ...

getMapper

Get the volume mapper

getRedrawMTime

Get the mtime of anything that would cause the rendered image to appear differently

getVolumes

For some exporters and other other operations we must be able to collect all the actors or volumes.

makeProperty

Create a new property suitable for use with this type of Actor.

Argument	Type	Required	Description
initialValues	IVolumePropertyInitialValues	No	(default: {})

newInstance

Method use to create a new instance of vtkVolume

setMapper

Set the volume mapper

Argument	Type	Required	Description
mapper	vtkVolumeMapper	Yes