RayCastIsosurface

Info

The example uses src/Testing/Data/FullHead.mhd which references src/Testing/Data/FullHead.raw.gz.

Description¶

This examples show how volume rendering can produce isosurface-like images. Using vtkOpenGLGPUVolumeRayCastMapper with an isosurface blend mode, two isosurfaces are created using appropriate transfer functions. The effect is similar to what is shown in MedicalDemo2. The user can specify the .mhd file and the two isosurface values. The example uses 500 and 1150 for the two isosurface values. The volume rendering "surfaces" are fuzzier than the hard surfaces created by vtkMarchingCubes in MedicalDemo3.

Usage

    RayCastIsosurface.py FullHead.mhd 500 1150

Info

The example uses src/Testing/Data/FullHead.mhd which references src/Testing/Data/FullHead.raw.gz.

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Question

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Code¶

RayCastIsosurface.py

#!/usr/bin/env python3

from dataclasses import dataclass
from pathlib import Path

# noinspection PyUnresolvedReferences
import vtkmodules.vtkInteractionStyle
# noinspection PyUnresolvedReferences
import vtkmodules.vtkRenderingOpenGL2
from vtkmodules.vtkCommonColor import vtkNamedColors
from vtkmodules.vtkCommonDataModel import vtkPiecewiseFunction
from vtkmodules.vtkIOImage import vtkMetaImageReader
from vtkmodules.vtkInteractionStyle import vtkInteractorStyleTrackballCamera
from vtkmodules.vtkRenderingCore import (
    vtkCamera,
    vtkColorTransferFunction,
    vtkRenderWindow,
    vtkRenderWindowInteractor,
    vtkRenderer,
    vtkVolume,
    vtkVolumeProperty
)
from vtkmodules.vtkRenderingVolumeOpenGL2 import vtkOpenGLGPUVolumeRayCastMapper


def get_program_parameters():
    import argparse
    description = 'Use volume rendering to produce an iso-surface-like image.'
    epilogue = '''

   '''
    parser = argparse.ArgumentParser(description=description, epilog=epilogue)
    parser.add_argument('filename', help='A required filename e.g. FullHead.mhd.')
    parser.add_argument('iso1', default=500, type=int, nargs='?', help='The first iso-contour.')
    parser.add_argument('iso2', default=1150, type=int, nargs='?', help='The second iso-contour.')
    args = parser.parse_args()
    return args.filename, args.iso1, args.iso2


def main():
    fn, iso1, iso2 = get_program_parameters()

    if not Path(fn).is_file():
        print(f'The path: {fn} does not exist.')
        return

    reader = vtkMetaImageReader(file_name=fn)

    colors = vtkNamedColors()

    mapper = vtkOpenGLGPUVolumeRayCastMapper(auto_adjust_sample_distances=False, sample_distance=0.5)
    reader >> mapper
    mapper.SetBlendModeToIsoSurface()

    iso1_rgb_pt_color = tuple(colors.GetColor3d('flesh'))
    iso2_rgb_pt_color = tuple(colors.GetColor3d('ivory'))
    color_transfer_function = vtkColorTransferFunction()
    color_transfer_function.RemoveAllPoints()
    color_transfer_function.AddRGBPoint(iso1, *iso1_rgb_pt_color)
    color_transfer_function.AddRGBPoint(iso2, *iso2_rgb_pt_color)

    scalar_opacity = vtkPiecewiseFunction()
    scalar_opacity.AddPoint(iso1, 0.3)
    scalar_opacity.AddPoint(iso2, 0.6)

    volume_property = vtkVolumeProperty(shade=True,
                                        interpolation_type=VolumeProperty.InterpolationType.VTK_LINEAR_INTERPOLATION,
                                        color=color_transfer_function, scalar_opacity=scalar_opacity)

    volume = vtkVolume(mapper=mapper, property=volume_property)

    renderer = vtkRenderer(background=colors.GetColor3d('cornflower'))
    renderer.AddVolume(volume)
    renderer.ResetCamera()

    render_window = vtkRenderWindow(size=(800, 600), window_name='RayCastIsosurface')
    render_window.AddRenderer(renderer)

    style = vtkInteractorStyleTrackballCamera()

    interactor = vtkRenderWindowInteractor()
    interactor.render_window = render_window
    interactor.interactor_style = style

    # Add some contour values to draw iso-surfaces.
    volume_property.iso_surface_values.SetValue(0, iso1)
    volume_property.iso_surface_values.SetValue(1, iso2)

    # Generate a good view.
    camera = vtkCamera()
    camera.view_up = (0, 0, -1)
    camera.position = (0, -1, 0)
    camera.focal_point = (0, 0, 0)

    renderer.active_camera = camera
    renderer.ResetCamera()

    camera.Azimuth(30.0)
    camera.Elevation(30.0)
    camera.Dolly(1.5)
    renderer.ResetCameraClippingRange()

    render_window.Render()

    interactor.Start()


@dataclass(frozen=True)
class VolumeProperty:
    @dataclass(frozen=True)
    class InterpolationType:
        VTK_NEAREST_INTERPOLATION: int = 0
        VTK_LINEAR_INTERPOLATION: int = 1
        VTK_CUBIC_INTERPOLATION: int = 2


if __name__ == '__main__':
    main()