SoVolumeRender - Man Page

enum Interpolation { NEAREST, LINEAR }
enum Composition { MAX_INTENSITY, SUM_INTENSITY, ALPHA_BLENDING }
enum NumSlicesControl { ALL, MANUAL, AUTOMATIC }
enum AbortCode { CONTINUE, ABORT, SKIP }
typedef AbortCode SoVolumeRenderAbortCB(int totalslices, int thisslice, void *userdata)

void setAbortCallback (SoVolumeRenderAbortCB *func, void *userdata=NULL)

static void initClass (void)

SoSFEnum interpolation
SoSFEnum composition
SoSFBool lighting
SoSFVec3f lightDirection
SoSFFloat lightIntensity
SoSFEnum numSlicesControl
SoSFInt32 numSlices
SoSFBool viewAlignedSlices

virtual void GLRender (SoGLRenderAction *action)
virtual void rayPick (SoRayPickAction *action)
virtual void generatePrimitives (SoAction *action)
virtual void computeBBox (SoAction *action, SbBox3f &box, SbVec3f &center)

class SoVolumeRenderP

The function signature for callback function pointers to be passed in to SoVolumeRender::setAbortCallback().

totalslices is the total number of textured slices that is expected to be rendered, unless the callback choose to abort or skip any of them.

thisslice is the index number of the next slice to render. Note that they are rendered back-to-front, and that they are numbered from 1 to totalslices.

userdata is the second argument given to SoVolumeRender::setAbortCallback() when the callback was set up.

Enumeration of available types of voxel colors interpolation.

Enumerator

NEAREST

For 'in between' pixels of the screen rasterization, pick the color of the nearest voxel. Will give sharp edges and a distinct blocky look.

LINEAR

For 'in between' pixels of the screen rasterization, interpolate by averaging the colors of several of the nearest voxels. Will give a smoother appearance, but sacrifies some 'correctness' for appearance.

Enumeration of available types of composition for partly translucent volumes.

Enumerator

MAX_INTENSITY

For each on-screen projected pixel, the voxel with the highest alpha intensity along that projection ray will be rendered.

This is for instance useful in medical imaging as a contrast enhancing operator for visualizing blood-flows.

Note that the availability of this composition mode for rendering with 2D- and 3D-textureslices will be dependent on features of the underlying rendering library.

(Specifically, the OpenGL driver must support glBlendEquation(), which is part of the optional 'imaging' API-subset of OpenGL version 1.2 and later.)

SUM_INTENSITY

For each on-screen projected pixel, the intensity of all voxels along that projection ray will be summed up before rendering.

This gives an appearance similar to medical X-ray images. The blending function is known as the 'attenuate' operator.

Note that the availability of this composition mode for rendering with 2D- and 3D-textureslices will be dependent on features of the underlying rendering library.

(Specifically, the OpenGL driver must support glBlendEquation(), which is part of the optional 'imaging' API-subset of OpenGL version 1.2 and later.)

ALPHA_BLENDING

Composes volume by rendering voxels with higher opacity such that they progressively obscures voxels behind them.

This is an approximation of the visual appearance of the penetration and reflection of light through a transparent material.

The blending function for this is known as the 'over' operator.

Enumeration of strategies for how to render the slices of the volume.

Enumerator

ALL

Always render as many slices as there are voxels in the depth dimension. This is the default value.

Please note that SoVolumeRender::NumSlicesControl will always be considered as SoVolumeRender::ALL if the SoVolumeRender::numSlices field is less or equal to 0.

MANUAL

Render as many slices as given by the SoVolumeRender::numSlices field.

AUTOMATIC

The number of slices to render will be calculated as follows:

unsigned int numslices = complexity * 2.0f * this->numSlices;

Where 'complexity' is the current SoComplexity::value setting in the scene graph traversal state. The default complexity value for a scene graph with no SoComplexity node(s) is 0.5.

For 'this->numSlices', see SoVolumeRender::numSlices.

The set of valid values that should be returned from a function set up in SoVolumeRender::setAbortCallback().

Enumerator

CONTINUE

Continue rendering in the usual manner.

ABORT

Don't render any more textured slices of the volume.

SKIP

Skip the next textured slice, and resume rendering on the next after that. (The abort callback function will still be called again.)

Lets the application programmer supply a callback function, by which it will be possible to either prematurely abort the rendering of a set of slices, or to skip certain slices.

Both of these measures are of course optimizations of rendering performance controlled from client code.

Picking of a volume doesn't work in quite the same manner as picking polygon geometry: the SoPickedPoint set up in the SoRayPickAction class will only contain the entry point of the ray into the volume.

For further picking information, grab the detail object and cast it to an SoVolumeRenderDetail (after first checking that it is of this type, of course).

References SoVolumeDetail::setDetails().

How to interpolate color values when rendering 'in between' voxels. See SoVolumeRender::Interpolation.

Default value is SoVolumeRender::LINEAR.

How to compose the projected volume rendering. See SoVolumeRender::Composition.

Default value is SoVolumeRender::ALPHA_BLENDING.

Specifies a strategy to use for calculating the number of slices to use for the visualization. The more slicer, the better quality and more correct the visualization will be, but the trade-off is that it will also influence the rendering performance.

The default value is SoVolumeRender::ALL.

(The rendering performance can be severly improved by changing this field's value to either SoVolumeRender::MANUAL or SoVolumeRender::AUTOMATIC, and then tuning the SoVolumeRender::numSlices field.)

Decides how many slices to render if SoVolumeRender::numSlicesControl is set to either SoVolumeRender::MANUAL or SoVolumeRender::AUTOMATIC.

For MANUAL, it sets an absolute number. For AUTOMATIC, a calculation will be done based on the value of this field and the current SoComplexity::value setting in the scene graph traversal state.

Note that the default value of the field is 0.