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3D Renderer

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Bernhard Froehler edited this page Sep 4, 2024 · 14 revisions

Up to Core widgets.

This widget shows a 3D rendering of the datasets for which this is activated in the dataset list; rendering settings can be adapted by editing the dataset parameters in the dataset list; for volumes, the transfer functions used for rendering can be specified in the Histogram widget for the dataset.

Navigation works mainly via mouse, you can:

  • Mouse Drag (Left-clicking and then moving) the mouse rotates the view around the dataset center
  • Shift + Mouse Drag moves the camera sideways
  • Ctrl + Mouse Drag rotates the camera around the place where the datasets are shown
  • Mousewheel up/down or Ctrl + Shift + Mouse Drag changes the zoom level

If you have multiple datasets that you want to show in context to one another, you can use the 3D Magic Lens.

In the top section of the rendering widget, there is a button bar:

Via the +X/-X, +Y/-Y, +Z/-Z, Iso buttons you can set the camera direction (the renderer typically starts with camera direction Iso). You can also store a screenshot of the current view, or a movie of the rotation of the shown dataset around one of the three coordinate system axes. The rightmost button enlarges the 3D renderer to take up all the space in the current window.

Key Commands

When the 3D renderer window is highlighted (click on it once to highlight it), several key commands are available:

  • 'r' resets the view
  • 'j' switches to joystick navigation mode
  • 't' switches to trackball navigation mode (the default navigation mode)
  • 'a' switches to actor modification mode (a single volume or polygon will be modified through the interaction)
  • 'c' switches to camera modification mode (interaction will again modify the camera perspective - the default modification mode)

When the "Cut plane" mode is enabled (via the "scissors" symbol in the dataset list):

  • pressing the 'x', 'y' and 'z' keys will switch the cutting direction of the respective axis ('y' will for example switch the slicing direction in the xz-plane).

Settings

You have access to a 3D renderer's settings by right-clicking on the renderer and clicking "Settings" in the appearing context menu. Via Edit-> Default Settings -> View: 3D Renderer you can change the default settings for any 3D render window opened in the future. These are the available settings:

  • Show slice planes (default: false) - determines whether the planes of the three axis aligned slicers are visualized as colored planes in the 3D renderer
  • Slice Plane Opacity (default: 1) - the opacity of the planes shown when checking the box for "Show slice planes".
  • Show Axes Cube (default: true) - determines whether to show the cube indicating axis directions
  • Show Origin Indicator (default true) - determines whether the origin is indicated by colored axes arrows
  • Show position (default: true) - shows a red cube indicating the current position of the mouse in the slicer (only updated when "Link Views" option in slicer settings is also enabled!)
  • Parallel projection (default: false) - whether the 3D renderer uses parallel projection or the standard perspective projection.
  • Background top (default: #7FAAFF), Background bottom (default: #FFFFFF) - colors used for the renderer background (gradient from top to bottom).
  • Use Fast Approximate Anti-Aliasing (default: true) - whether the 3D renderer should use (fast approximate) anti-aliasing (FXAA). This will reduce so-called aliasing effects ("stair-case"-like appearance of straight lines).
  • MultiSamples (default: 0) - number of multi-samples to use for hardware anti-aliasing; needs to be 0 for depth peeling to work!
  • Use Depth Peeling (default: true) - whether rendering of translucent material with the depth peeling technique should be enabled
  • Depth Peels Occlusion Ratio (default: 0) - In case of depth peeling enabled, defines the threshold under which the algorithm stops to iterate over peel layers. This is the ratio of the number of pixels that have been touched by the last layer over the total number of pixels of the viewport area. A value of 0.0 means that rendering has to be exact. Greater values may speed-up the rendering with small impact on the quality.
  • Depth Peels Maximum Number (default: 4) - In case of depth peeling enabled, define the maximum number of peeling layers. A special value of 0 means no maximum limit; it has to be a positive value.
  • Magic Lens Size (default: 120) - the size of the 3D magic lens
  • Magic Lens Frame Width (default: 3) - the width of the border of the 3D magic lens
  • Show Frames Per Second (default: false) - if enabled, every time the render window is updated, a (Debug level) output message is written that gives the the theoretical number of frames per second (if rendering were repeated continuously - currently updates are only triggered when some change requiring a re-rending is detected)
  • Use Screen Space Ambient Occlusion (default: false) - whether to use Screen Space Ambient Occlusion (SSAO). This technique darkens some pixels to improve depth perception.
  • Screen Space Ambient Occlusion Radius (default: 0.5) - SSAO: The hemisphere radius
  • Screen Space Ambient Occlusion Bias (default: 0.01) - SSAO: The bias when comparing samples
  • Screen Space Ambient Occlusion Kernel Size (default: 32) - SSAO: The number of samples
  • Screen Space Ambient Occlusion Blur (default: false) - SSAO: Whether the ambient occlusion should be blurred (can help to improve the result if samples number is low).

For changing aspects about how a specific dataset is shown, see also the dataset parameters available through the dataset list.

open_iA Documentation, licensed under CC BY-NC-SA 4.0

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