Iso-Surfaces

To add a rendered iso-surface to the 3-D display, select Load Iso-Surface ... from the File menu of the 3-D Viewer: 3d_file_iso_surface

A dialog will now appear, from which you can select the image from which the iso-surface will be extracted and displayed.

3d_iso_surface_dialog

First, select the image you want to work with by clicking on the open icon, by typing in the folder (directory) and file name of the image, or by pressing the right mouse button and selecting from the menu of recently-used images.

input_image

This will automatically generate and display an iso-surface at an intensity level that is automatically selected. You can now make the following adjustments to change how the iso-surface is displayed.

  • Iso-surface intensity threshold. This sets the intensity level at which the iso-surface is extracted.

    3d_threshold_slider

    Move the slider to the left and right to set the iso-surface intensity to a different value. Note that calculation of the iso-surface and redisplay may take a few seconds after you adjust the threshold slider.

  • Surface opacity. The surface opacity has a value between 0 (completely transparent) and 1 (completely opaque). Change the opacity using the opacity slider.

    Opacity slider

  • Surface colour. The default colour with which the iso-surface is rendered is grey. To change the colour, click on the 3d_colour_button button and select the new colour from the colour chooser that will pop up.

    Note: if the loaded image is a colour image, then an additional option will appear:

    Checkbox to set per-vertex colours for colour image isosurfaces

    When selected, the colour of each triangle vertex in the iso-surface will be set from the colour of the image at that point, rather than the iso-surface having a uniform colour.

  • Surface shininess. The surface shininess has a value between 1 and 128. Change the shininess using the 3d_shininess_spinner spinner.

  • Render mode. The surface is defined by an array of linked triangles, and can be rendered as:

    • A solid surface. Select a render mode of "Fill".
    • A triangulated mesh. Select a render mode of "Wire frame".
    • A cloud of points. Select a render mode of "Points".

    The images below show the same 3-D iso-surface rendered in these three modes.

    An iso-surface rendered using the three modes.
    3d_fill 3d_wire_frame 3d_points
    Fill Wire frame Points

  • Surface fidelity. Setting the surface fidelity determines the number of triangles that will be calculated to define the surface - the greater the number of triangles, better will be the fidelity. However, the better the surface fidelity, the more time will be required to compute and display the surface. The images below show the same a 3-D dataset rendered with the three levels of fidelity.

    An iso-surface generated with three levels of fidelity.
    3d_fidelity_low 3d_fidelity_medium 3d_fidelity_high
    Low Medium High

    Using a low or medium surface fidelity setting causes the original dataset to be re-sampled to a lower spatial resolution so that the number of surface triangles is reduced. This has the effect of smoothing the iso-surface.

The effect of selecting the cut_away_checkbox check-box is dealt with in the section about general controls.

If you click the done_button button, the iso-surface will be removed from the 3-D viewer.