VolumeProperty

Introduction

vtkVolumeProperty is used to represent common properties associated
with volume rendering. This includes properties for determining the type
of interpolation to use when sampling a volume, the color of a volume,
the scalar opacity of a volume, the gradient opacity of a volume, and the
shading parameters of a volume.

When the scalar opacity or the gradient opacity of a volume is not set,
then the function is defined to be a constant value of 1.0. When a
scalar and gradient opacity are both set simultaneously, then the opacity
is defined to be the product of the scalar opacity and gradient opacity
transfer functions.

Most properties can be set per “component” for volume mappers that
support multiple independent components. If you are using 2 component
data as LV or 4 component data as RGBV (as specified in the mapper)
only the first scalar opacity and gradient opacity transfer functions
will be used (and all color functions will be ignored). Omitting the
index parameter on the Set/Get methods will access index = 0.

When independent components is turned on, a separate feature (useful
for volume rendering labelmaps) is available. By default all components
have an “opacityMode” of FRACTIONAL, which results in the usual
addition of that components scalar opacity function value to the final
opacity of the fragment. By setting one or more components to have a
PROPORTIONAL “opacityMode” instead, the scalar opacity lookup value
for those components will not be used to adjust the fragment opacity,
but rather used to multiply the color of that fragment. This kind of
rendering makes sense for labelmap components because the gradient of
those fields is meaningless and should not be used in opacity
computation. At the same time, multiplying the color value by the
piecewise scalar opacity function value provides an opportunity to
design piecewise constant opacity functions (step functions) that can
highlight any subset of label values.

vtkColorTransferFunction is a color mapping in RGB or HSV space that
uses piecewise hermite functions to allow interpolation that can be
piecewise constant, piecewise linear, or somewhere in-between
(a modified piecewise hermite function that squishes the function
according to a sharpness parameter). The function also allows for
the specification of the midpoint (the place where the function
reaches the average of the two bounding nodes) as a normalize distance
between nodes.

See the description of class vtkPiecewiseFunction for an explanation of
midpoint and sharpness.

Usage

// 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);

// set them on the property
volume.getProperty().setRGBTransferFunction(0, ctfun);
volume.getProperty().setScalarOpacity(0, ofun);
volume.getProperty().setScalarOpacityUnitDistance(0, 4.5);
volume.getProperty().setInterpolationTypeToLinear();

Methods

extend

Method use to decorate a given object (publicAPI+model) with vtkVolumeProperty 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	IVolumePropertyInitialValues	No	(default: {})

getAmbient

Get the ambient lighting coefficient.

getColorChannels

Argument	Type	Required	Description
index	Number	Yes

getComponentWeight

Get the scalar component weights.

Argument	Type	Required	Description
index	Number	Yes

getDiffuse

Get the diffuse lighting coefficient.

getGradientOpacityMaximumOpacity

Argument	Type	Required	Description
index	Number	Yes

getGradientOpacityMaximumValue

Argument	Type	Required	Description
index	Number	Yes

getGradientOpacityMinimumOpacity

Argument	Type	Required	Description
index	Number	Yes

getGradientOpacityMinimumValue

Argument	Type	Required	Description
index	Number	Yes

getGrayTransferFunction

Get the currently set gray transfer function. Create one if none set.

Argument	Type	Required	Description
index	Number	Yes

getIndependentComponents

getInterpolationType

Get the interpolation type for sampling a volume.

getInterpolationTypeAsString

Get the interpolation type for sampling a volume as a string.

getLabelOutlineThickness

getMTime

Return 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? …

getOpacityMode

getRGBTransferFunction

Get the currently set RGB transfer function. Create one if none set.

Argument	Type	Required	Description
index	Number	Yes

getScalarOpacity

Get the scalar opacity transfer function. Create one if none set.

Argument	Type	Required	Description
index	Number	Yes

getScalarOpacityUnitDistance

Get the unit distance on which the scalar opacity transfer function is defined.

Argument	Type	Required	Description
index	Number	Yes

getShade

Get the shading of a volume.

getSpecular

getSpecularPower

Get the specular power.

getUseGradientOpacity

Argument	Type	Required	Description
index	Number	Yes

getUseLabelOutline

newInstance

Method use to create a new instance of vtkVolumeProperty

setAmbient

Set the ambient lighting coefficient.

Argument	Type	Required	Description
ambient	Number	Yes	The ambient lighting coefficient.

setComponentWeight

Set the scalar component weights.

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setDiffuse

Set the diffuse lighting coefficient.

Argument	Type	Required	Description
diffuse	Number	Yes	The diffuse lighting coefficient.

setGradientOpacityMaximumOpacity

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setGradientOpacityMaximumValue

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setGradientOpacityMinimumOpacity

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setGradientOpacityMinimumValue

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setGrayTransferFunction

Set the color of a volume to a gray transfer function

Argument	Type	Required	Description
index	Number	Yes
func	vtkPiecewiseFunction	Yes

setIndependentComponents

Does the data have independent components, or do some define color only?
If IndependentComponents is On (the default) then each component will be
independently passed through a lookup table to determine RGBA, shaded.

Some volume Mappers can handle 1 to 4 component unsigned char or unsigned
short data (see each mapper header file to determine functionality). If
IndependentComponents is Off, then you must have either 2 or 4 component
data. For 2 component data, the first is passed through the first color
transfer function and the second component is passed through the first
scalar opacity (and gradient opacity) transfer function. Normals will be
generated off of the second component. When using gradient based opacity
modulation, the gradients are computed off of the second component. For 4
component data, the first three will directly represent RGB (no lookup
table). The fourth component will be passed through the first scalar
opacity transfer function for opacity and first gradient opacity transfer
function for gradient based opacity modulation. Normals will be generated
from the fourth component. When using gradient based opacity modulation,
the gradients are computed off of the fourth component.

Argument	Type	Required	Description
independentComponents	Boolean	Yes

setInterpolationType

Set the interpolation type for sampling a volume.

Argument	Type	Required	Description
interpolationType	InterpolationType	Yes

setInterpolationTypeToFastLinear

Set interpolation type to FAST_LINEAR

setInterpolationTypeToLinear

Set interpolation type to LINEAR

setInterpolationTypeToNearest

Set interpolation type to NEAREST

setLabelOutlineThickness

It will set the label outline thickness for the labelmaps. It can accept
a single number or an array of numbers. If a single number is provided,
it will be used for all the segments. If an array is provided, it indicates
the thickness for each segment index. For instance if you have a labelmap
with 3 segments (0: background 1: liver 2: tumor), you can set the thickness
to [2,4] to have a thicker outline for the tumor (thickness 4). It should be
noted that the thickness is in pixel and also the first array value will
control the default thickness for all labels when 0 or not specified.

Argument	Type	Required	Description
labelOutlineThickness	Number or Array.	Yes

setOpacityMode

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setRGBTransferFunction

Set the color of a volume to an RGB transfer function

Argument	Type	Required	Description
index	Number	Yes
func	vtkColorTransferFunction	Yes

setScalarOpacity

Set the scalar opacity of a volume to a transfer function

Argument	Type	Required	Description
index	Number	Yes
func	vtkPiecewiseFunction	Yes

setScalarOpacityUnitDistance

Set the unit distance on which the scalar opacity transfer function is
defined.

Argument	Type	Required	Description
index	Number	Yes
value	Number	Yes

setShade

Set the shading of a volume.

If shading is turned off, then the mapper for the volume will not perform
shading calculations. If shading is turned on, the mapper may perform
shading calculations - in some cases shading does not apply (for example,
in a maximum intensity projection) and therefore shading will not be
performed even if this flag is on. For a compositing type of mapper,
turning shading off is generally the same as setting ambient=1,
diffuse=0, specular=0. Shading can be independently turned on/off per
component.

Argument	Type	Required	Description
shade	Boolean	Yes

setSpecular

Argument	Type	Required	Description
specular	Number	Yes

setSpecularPower

Set the specular power.

Argument	Type	Required	Description
specularPower	Number	Yes

setUseGradientOpacity

Argument	Type	Required	Description
index	Number	Yes
value	Boolean	Yes

setUseLabelOutline

Argument	Type	Required	Description
useLabelOutline	Boolean	Yes

Source

Constants.d.ts

export declare enum InterpolationType {
	NEAREST = 0,
	LINEAR = 1,
	FAST_LINEAR = 2
}

export declare enum OpacityMode {
	FRACTIONAL = 0,
	PROPORTIONAL = 1,
}

declare const _default: {
	InterpolationType: typeof InterpolationType;
	OpacityMode: typeof OpacityMode;
};
export default _default;

Constants.js

export const InterpolationType = {
  NEAREST: 0,
  LINEAR: 1,
  FAST_LINEAR: 2,
};

export const OpacityMode = {
  FRACTIONAL: 0,
  PROPORTIONAL: 1,
};

export default {
  InterpolationType,
  OpacityMode,
};

index.d.ts

import vtkPiecewiseFunction from "../../../Common/DataModel/PiecewiseFunction";
import { vtkObject } from "../../../interfaces";
import vtkColorTransferFunction from "../ColorTransferFunction";
import { InterpolationType, OpacityMode } from "./Constants";

export interface IVolumePropertyInitialValues  {
	independentComponents?: boolean;
	shade?: boolean;
	ambient?: number;
	diffuse?: number;
	specular?: number;
	specularPower?: number;
	useLabelOutline?: boolean;
	labelOutlineThickness?: number;
}

export interface vtkVolumeProperty extends vtkObject {

	/**
	 * Get the ambient lighting coefficient.
	 */
	getAmbient(): number;

	/**
	 * Return 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? ...
	 *
	 * @return {Number} the global modified time.
	 */
	getMTime(): number;

	/**
	 *
	 * @param {Number} index
	 */
	getColorChannels(index: number): number;

	/**
	 * Get the diffuse lighting coefficient.
	 */
	getDiffuse(): number;

	/**
	 *
	 * @param {Number} index
	 */
	getGradientOpacityMaximumOpacity(index: number): number;

	/**
	 *
	 * @param {Number} index
	 */
	getGradientOpacityMaximumValue(index: number): number;

	/**
	 *
	 * @param {Number} index
	 */
	getGradientOpacityMinimumOpacity(index: number): number;

	/**
	 *
	 * @param {Number} index
	 */
	getGradientOpacityMinimumValue(index: number): number;

	/**
	 *
	 */
	getIndependentComponents(): boolean;

	/**
	 * Get the unit distance on which the scalar opacity transfer function is defined.
	 * @param {Number} index
	 */
	getScalarOpacityUnitDistance(index: number): number;

	/**
	 * Get the currently set gray transfer function. Create one if none set.
	 * @param {Number} index
	 */
	getGrayTransferFunction(index: number): vtkPiecewiseFunction;

	/**
	 *
	 * @default FRACTIONAL
	 */
	getOpacityMode(index: number): OpacityMode;

	/**
	 *
	 */
	getLabelOutlineThickness(): number;

	/**
	 * Get the currently set RGB transfer function. Create one if none set.
	 * @param {Number} index 
	 */
	getRGBTransferFunction(index: number): vtkColorTransferFunction;

	/**
	 * Get the scalar opacity transfer function. Create one if none set.
	 * @param {Number} index 
	 */
	getScalarOpacity(index: number): vtkPiecewiseFunction;

	/**
	 * Get the shading of a volume.
	 */
	getShade(): boolean;

	/**
	 *
	 */
	getSpecular(): number;

	/**
	 * Get the specular power.
	 */
	getSpecularPower(): number;

	/**
	 *
	 * @param {Number} index 
	 */
	getUseGradientOpacity(index: number): boolean;

	/**
	 *
	 */
	getUseLabelOutline(): boolean;

	/**
	 * Set the ambient lighting coefficient.
	 * @param {Number} ambient The ambient lighting coefficient.
	 */
	setAmbient(ambient: number): boolean;

	/**
	 * Set the diffuse lighting coefficient.
	 * @param {Number} diffuse The diffuse lighting coefficient.
	 */
	setDiffuse(diffuse: number): boolean;

	/**
	 *
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setGradientOpacityMaximumOpacity(index: number, value: number): boolean;

	/**
	 *
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setGradientOpacityMaximumValue(index: number, value: number): boolean;

	/**
	 *
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setGradientOpacityMinimumOpacity(index: number, value: number): boolean;

	/**
	 *
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setGradientOpacityMinimumValue(index: number, value: number): boolean;

	/**
	 * Set the color of a volume to a gray transfer function
	 * @param {Number} index 
	 * @param {vtkPiecewiseFunction} func 
	 */
	setGrayTransferFunction(index: number, func: vtkPiecewiseFunction): boolean;

	/**
	 * Does the data have independent components, or do some define color only?
	 * If IndependentComponents is On (the default) then each component will be
	 * independently passed through a lookup table to determine RGBA, shaded.
	 *
	 * Some volume Mappers can handle 1 to 4 component unsigned char or unsigned
	 * short data (see each mapper header file to determine functionality). If
	 * IndependentComponents is Off, then you must have either 2 or 4 component
	 * data. For 2 component data, the first is passed through the first color
	 * transfer function and the second component is passed through the first
	 * scalar opacity (and gradient opacity) transfer function. Normals will be
	 * generated off of the second component. When using gradient based opacity
	 * modulation, the gradients are computed off of the second component. For 4
	 * component data, the first three will directly represent RGB (no lookup
	 * table). The fourth component will be passed through the first scalar
	 * opacity transfer function for opacity and first gradient opacity transfer
	 * function for gradient based opacity modulation. Normals will be generated
	 * from the fourth component. When using gradient based opacity modulation,
	 * the gradients are computed off of the fourth component.
	 * @param {Boolean} independentComponents
	 */
	setIndependentComponents(independentComponents: boolean): boolean;

	/**
	 * It will set the label outline thickness for the labelmaps. It can accept
	 * a single number or an array of numbers. If a single number is provided,
	 * it will be used for all the segments. If an array is provided, it indicates
	 * the thickness for each segment index. For instance if you have a labelmap
	 * with 3 segments (0: background 1: liver 2: tumor), you can set the thickness
	 * to [2,4] to have a thicker outline for the tumor (thickness 4). It should be 
	 * noted that the thickness is in pixel and also the first array value will 
	 * control the default thickness for all labels when 0 or not specified.
	 * 
	 * @param {Number | Number[]} labelOutlineThickness
	 */
	setLabelOutlineThickness(labelOutlineThickness: number | number[]): boolean;


	/**
	 *
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setOpacityMode(index: number, value: number): boolean;

	/**
	 * Set the unit distance on which the scalar opacity transfer function is
	 * defined.
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setScalarOpacityUnitDistance(index: number, value: number): boolean;

	/**
	 * Set the shading of a volume.
	 * 
	 * If shading is turned off, then the mapper for the volume will not perform
	 * shading calculations. If shading is turned on, the mapper may perform
	 * shading calculations - in some cases shading does not apply (for example,
	 * in a maximum intensity projection) and therefore shading will not be
	 * performed even if this flag is on. For a compositing type of mapper,
	 * turning shading off is generally the same as setting ambient=1,
	 * diffuse=0, specular=0. Shading can be independently turned on/off per
	 * component.
	 * @param {Boolean} shade
	 */
	setShade(shade: boolean): boolean;

	/**
	 *
	 * @param {Number} specular
	 */
	setSpecular(specular: number): boolean;

	/**
	 * Set the specular power.
	 * @param {Number} specularPower
	 */
	setSpecularPower(specularPower: number): boolean;

	/**
	 *
	 * @param {Number} index 
	 * @param {Boolean} value 
	 */
	setUseGradientOpacity(index: number, value: boolean): boolean;

	/**
	 *
	 * @param {Boolean} useLabelOutline 
	 */
	setUseLabelOutline(useLabelOutline: boolean): boolean;

	/**
	 * Set the color of a volume to an RGB transfer function
	 * @param {Number} index 
	 * @param {vtkColorTransferFunction} func 
	 */
	setRGBTransferFunction(index: number, func: vtkColorTransferFunction): boolean;

	/**
	 * Set the scalar opacity of a volume to a transfer function
	 * @param {Number} index 
	 * @param {vtkPiecewiseFunction} func 
	 */
	setScalarOpacity(index: number, func: vtkPiecewiseFunction): boolean;

	/**
	 * Set the scalar component weights.
	 * @param {Number} index 
	 * @param {Number} value 
	 */
	setComponentWeight(index: number, value: number): boolean;

	/**
	 * Get the scalar component weights.
	 * @param {Number} index 
	 */
	getComponentWeight(index: number): number;

	/**
	 * Set the interpolation type for sampling a volume.
	 * @param {InterpolationType} interpolationType 
	 */
	setInterpolationType(interpolationType: InterpolationType): boolean;

	/**
	 * Set interpolation type to NEAREST
	 */
	setInterpolationTypeToNearest(): boolean;

	/**
	 * Set interpolation type to LINEAR
	 */
	setInterpolationTypeToLinear(): boolean;

	/**
	 * Set interpolation type to FAST_LINEAR
	 */
	setInterpolationTypeToFastLinear(): boolean;

	/**
	 * Get the interpolation type for sampling a volume.
	 */
	getInterpolationType(): InterpolationType;

	/**
	 * Get the interpolation type for sampling a volume as a string.
	 */
	getInterpolationTypeAsString(): string;
}

/**
 * Method use to decorate a given object (publicAPI+model) with vtkVolumeProperty characteristics.
 *
 * @param publicAPI object on which methods will be bounds (public)
 * @param model object on which data structure will be bounds (protected)
 * @param {IVolumePropertyInitialValues} [initialValues] (default: {})
 */
export function extend(publicAPI: object, model: object, initialValues?: IVolumePropertyInitialValues): void;

/**
 * Method use to create a new instance of vtkVolumeProperty
 */
export function newInstance(initialValues?: IVolumePropertyInitialValues): vtkVolumeProperty;

/**
 * vtkVolumeProperty is used to represent common properties associated
 * with volume rendering. This includes properties for determining the type
 * of interpolation to use when sampling a volume, the color of a volume,
 * the scalar opacity of a volume, the gradient opacity of a volume, and the
 * shading parameters of a volume.

 * When the scalar opacity or the gradient opacity of a volume is not set,
 * then the function is defined to be a constant value of 1.0. When a
 * scalar and gradient opacity are both set simultaneously, then the opacity
 * is defined to be the product of the scalar opacity and gradient opacity
 * transfer functions.
 *
 * Most properties can be set per "component" for volume mappers that
 * support multiple independent components. If you are using 2 component
 * data as LV or 4 component data as RGBV (as specified in the mapper)
 * only the first scalar opacity and gradient opacity transfer functions
 * will be used (and all color functions will be ignored). Omitting the
 * index parameter on the Set/Get methods will access index = 0.
 *
 * When independent components is turned on, a separate feature (useful
 * for volume rendering labelmaps) is available.  By default all components
 * have an "opacityMode" of `FRACTIONAL`, which results in the usual
 * addition of that components scalar opacity function value to the final
 * opacity of the fragment.  By setting one or more components to have a
 * `PROPORTIONAL` "opacityMode" instead, the scalar opacity lookup value
 * for those components will not be used to adjust the fragment opacity,
 * but rather used to multiply the color of that fragment.  This kind of
 * rendering makes sense for labelmap components because the gradient of
 * those fields is meaningless and should not be used in opacity
 * computation.  At the same time, multiplying the color value by the
 * piecewise scalar opacity function value provides an opportunity to
 * design piecewise constant opacity functions (step functions) that can
 * highlight any subset of label values.
 *
 * vtkColorTransferFunction is a color mapping in RGB or HSV space that
 * uses piecewise hermite functions to allow interpolation that can be
 * piecewise constant, piecewise linear, or somewhere in-between
 * (a modified piecewise hermite function that squishes the function
 * according to a sharpness parameter). The function also allows for
 * the specification of the midpoint (the place where the function
 * reaches the average of the two bounding nodes) as a normalize distance
 * between nodes.
 *
 * See the description of class vtkPiecewiseFunction for an explanation of
 * midpoint and sharpness.
 *
 * @example
 * ```js
 * // 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);
 *
 * // set them on the property
 * volume.getProperty().setRGBTransferFunction(0, ctfun);
 * volume.getProperty().setScalarOpacity(0, ofun);
 * volume.getProperty().setScalarOpacityUnitDistance(0, 4.5);
 * volume.getProperty().setInterpolationTypeToLinear();
 * ```
 */
export declare const vtkVolumeProperty: {
	newInstance: typeof newInstance;
	extend: typeof extend;
	InterpolationType: typeof InterpolationType;
	OpacityMode: typeof OpacityMode;
};
export default vtkVolumeProperty;

index.js

import macro from 'vtk.js/Sources/macros';
import vtkColorTransferFunction from 'vtk.js/Sources/Rendering/Core/ColorTransferFunction';
import vtkPiecewiseFunction from 'vtk.js/Sources/Common/DataModel/PiecewiseFunction';
import Constants from 'vtk.js/Sources/Rendering/Core/VolumeProperty/Constants';

const { InterpolationType, OpacityMode } = Constants;
const { vtkErrorMacro } = macro;

const VTK_MAX_VRCOMP = 4;

// ----------------------------------------------------------------------------
// vtkVolumeProperty methods
// ----------------------------------------------------------------------------

function vtkVolumeProperty(publicAPI, model) {
  // Set our className
  model.classHierarchy.push('vtkVolumeProperty');

  publicAPI.getMTime = () => {
    let mTime = model.mtime;
    let time;

    for (let index = 0; index < VTK_MAX_VRCOMP; index++) {
      // Color MTimes
      if (model.componentData[index].colorChannels === 1) {
        if (model.componentData[index].grayTransferFunction) {
          // time that Gray transfer function was last modified
          time = model.componentData[index].grayTransferFunction.getMTime();
          mTime = mTime > time ? mTime : time;
        }
      } else if (model.componentData[index].colorChannels === 3) {
        if (model.componentData[index].rGBTransferFunction) {
          // time that RGB transfer function was last modified
          time = model.componentData[index].rGBTransferFunction.getMTime();
          mTime = mTime > time ? mTime : time;
        }
      }

      // Opacity MTimes
      if (model.componentData[index].scalarOpacity) {
        // time that Scalar opacity transfer function was last modified
        time = model.componentData[index].scalarOpacity.getMTime();
        mTime = mTime > time ? mTime : time;
      }

      if (model.componentData[index].gradientOpacity) {
        if (!model.componentData[index].disableGradientOpacity) {
          // time that Gradient opacity transfer function was last modified
          time = model.componentData[index].gradientOpacity.getMTime();
          mTime = mTime > time ? mTime : time;
        }
      }
    }

    return mTime;
  };

  publicAPI.getColorChannels = (index) => {
    if (index < 0 || index > 3) {
      vtkErrorMacro('Bad index - must be between 0 and 3');
      return 0;
    }

    return model.componentData[index].colorChannels;
  };

  // Set the color of a volume to a gray transfer function
  publicAPI.setGrayTransferFunction = (index = 0, func = null) => {
    let modified = false;
    if (model.componentData[index].grayTransferFunction !== func) {
      model.componentData[index].grayTransferFunction = func;
      modified = true;
    }

    if (model.componentData[index].colorChannels !== 1) {
      model.componentData[index].colorChannels = 1;
      modified = true;
    }

    if (modified) {
      publicAPI.modified();
    }
    return modified;
  };

  // Get the currently set gray transfer function. Create one if none set.
  publicAPI.getGrayTransferFunction = (index = 0) => {
    if (model.componentData[index].grayTransferFunction === null) {
      model.componentData[index].grayTransferFunction =
        vtkPiecewiseFunction.newInstance();
      model.componentData[index].grayTransferFunction.addPoint(0, 0.0);
      model.componentData[index].grayTransferFunction.addPoint(1024, 1.0);
      if (model.componentData[index].colorChannels !== 1) {
        model.componentData[index].colorChannels = 1;
      }
      publicAPI.modified();
    }

    return model.componentData[index].grayTransferFunction;
  };

  // Set the color of a volume to an RGB transfer function
  publicAPI.setRGBTransferFunction = (index = 0, func = null) => {
    let modified = false;
    if (model.componentData[index].rGBTransferFunction !== func) {
      model.componentData[index].rGBTransferFunction = func;
      modified = true;
    }

    if (model.componentData[index].colorChannels !== 3) {
      model.componentData[index].colorChannels = 3;
      modified = true;
    }

    if (modified) {
      publicAPI.modified();
    }
    return modified;
  };

  // Get the currently set RGB transfer function. Create one if none set.
  publicAPI.getRGBTransferFunction = (index = 0) => {
    if (model.componentData[index].rGBTransferFunction === null) {
      model.componentData[index].rGBTransferFunction =
        vtkColorTransferFunction.newInstance();
      model.componentData[index].rGBTransferFunction.addRGBPoint(
        0,
        0.0,
        0.0,
        0.0
      );
      model.componentData[index].rGBTransferFunction.addRGBPoint(
        1024,
        1.0,
        1.0,
        1.0
      );
      if (model.componentData[index].colorChannels !== 3) {
        model.componentData[index].colorChannels = 3;
      }
      publicAPI.modified();
    }

    return model.componentData[index].rGBTransferFunction;
  };

  // Set the scalar opacity of a volume to a transfer function
  publicAPI.setScalarOpacity = (index = 0, func = null) => {
    if (model.componentData[index].scalarOpacity !== func) {
      model.componentData[index].scalarOpacity = func;
      publicAPI.modified();
      return true;
    }
    return false;
  };

  // Get the scalar opacity transfer function. Create one if none set.
  publicAPI.getScalarOpacity = (index = 0) => {
    if (model.componentData[index].scalarOpacity === null) {
      model.componentData[index].scalarOpacity =
        vtkPiecewiseFunction.newInstance();
      model.componentData[index].scalarOpacity.addPoint(0, 1.0);
      model.componentData[index].scalarOpacity.addPoint(1024, 1.0);
      publicAPI.modified();
    }

    return model.componentData[index].scalarOpacity;
  };

  publicAPI.setComponentWeight = (index = 0, value = 1) => {
    if (index < 0 || index >= VTK_MAX_VRCOMP) {
      vtkErrorMacro('Invalid index');
      return false;
    }

    const val = Math.min(1, Math.max(0, value));
    if (model.componentData[index].componentWeight !== val) {
      model.componentData[index].componentWeight = val;
      publicAPI.modified();
      return true;
    }
    return false;
  };

  publicAPI.getComponentWeight = (index = 0) => {
    if (index < 0 || index >= VTK_MAX_VRCOMP) {
      vtkErrorMacro('Invalid index');
      return 0.0;
    }

    return model.componentData[index].componentWeight;
  };

  publicAPI.setInterpolationTypeToNearest = () =>
    publicAPI.setInterpolationType(InterpolationType.NEAREST);

  publicAPI.setInterpolationTypeToLinear = () =>
    publicAPI.setInterpolationType(InterpolationType.LINEAR);

  publicAPI.setInterpolationTypeToFastLinear = () =>
    publicAPI.setInterpolationType(InterpolationType.FAST_LINEAR);

  publicAPI.getInterpolationTypeAsString = () =>
    macro.enumToString(InterpolationType, model.interpolationType);

  const sets = [
    'useGradientOpacity',
    'scalarOpacityUnitDistance',
    'gradientOpacityMinimumValue',
    'gradientOpacityMinimumOpacity',
    'gradientOpacityMaximumValue',
    'gradientOpacityMaximumOpacity',
    'opacityMode',
  ];
  sets.forEach((val) => {
    const cap = macro.capitalize(val);
    publicAPI[`set${cap}`] = (index, value) => {
      if (model.componentData[index][`${val}`] !== value) {
        model.componentData[index][`${val}`] = value;
        publicAPI.modified();
        return true;
      }
      return false;
    };
  });

  const gets = [
    'useGradientOpacity',
    'scalarOpacityUnitDistance',
    'gradientOpacityMinimumValue',
    'gradientOpacityMinimumOpacity',
    'gradientOpacityMaximumValue',
    'gradientOpacityMaximumOpacity',
    'opacityMode',
  ];
  gets.forEach((val) => {
    const cap = macro.capitalize(val);
    publicAPI[`get${cap}`] = (index) => model.componentData[index][`${val}`];
  });
}

// ----------------------------------------------------------------------------
// Object factory
// ----------------------------------------------------------------------------

const DEFAULT_VALUES = {
  independentComponents: true,
  interpolationType: InterpolationType.FAST_LINEAR,
  shade: false,
  ambient: 0.1,
  diffuse: 0.7,
  specular: 0.2,
  specularPower: 10.0,
  useLabelOutline: false,
  labelOutlineThickness: [1],
  labelOutlineOpacity: 1.0,
};

// ----------------------------------------------------------------------------

export function extend(publicAPI, model, initialValues = {}) {
  Object.assign(model, DEFAULT_VALUES, initialValues);

  // Build VTK API
  macro.obj(publicAPI, model);

  if (!model.componentData) {
    model.componentData = [];
    for (let i = 0; i < VTK_MAX_VRCOMP; ++i) {
      model.componentData.push({
        colorChannels: 1,
        grayTransferFunction: null,
        rGBTransferFunction: null,
        scalarOpacity: null,
        scalarOpacityUnitDistance: 1.0,
        opacityMode: OpacityMode.FRACTIONAL,

        gradientOpacityMinimumValue: 0,
        gradientOpacityMinimumOpacity: 0.0,
        gradientOpacityMaximumValue: 1.0,
        gradientOpacityMaximumOpacity: 1.0,
        useGradientOpacity: false,

        componentWeight: 1.0,
      });
    }
  }

  macro.setGet(publicAPI, model, [
    'independentComponents',
    'interpolationType',
    'shade',
    'ambient',
    'diffuse',
    'specular',
    'specularPower',
    'useLabelOutline',
    'labelOutlineOpacity',
  ]);

  macro.setGetArray(publicAPI, model, ['labelOutlineThickness']);

  // Object methods
  vtkVolumeProperty(publicAPI, model);
}

// ----------------------------------------------------------------------------

export const newInstance = macro.newInstance(extend, 'vtkVolumeProperty');

// ----------------------------------------------------------------------------

export default { newInstance, extend, ...Constants };