com.openinventor.volumeviz.nodes

Class SoVolumeClippingGroup

java.lang.Object

com.openinventor.inventor.Inventor

com.openinventor.inventor.misc.SoBase

com.openinventor.inventor.fields.SoFieldContainer

com.openinventor.inventor.nodes.SoNode

com.openinventor.inventor.nodes.SoGroup

com.openinventor.volumeviz.nodes.SoVolumeClippingGroup

All Implemented Interfaces:

SafeDisposable

public class SoVolumeClippingGroup
extends SoGroup

Clipping a volume with a 3D object. VolumeViz supports clipping a volume against any closed 3D polygonal shape defined by standard Open Inventor geometry. This is done using the SoVolumeClippingGroup node. Polygon clipping can remove the voxels outside the shape or the voxels inside the shape. Polygon clipping can be used in seismic applications to clip outside a fault block or geobody, in medical applications to cut away an arbitrary region, in core sample applications to apply cylindrical clipping and many other uses.

When this node is in the scene graph before a VolumeViz rendering node, all shapes under the SoVolumeClippingGroup will be used to clip the volume. These shapes will not be displayed.

The geometry defined under SoVolumeClippingGroup must represent a set of closed surfaces otherwise the result is unpredictable.

The clipping group may include transform nodes, e.g. SoTransform, to scale, rotate and translate the geometry. The transformed geometry will be used for clipping.

In general, do not put draggers or manipulators, e.g. SoTabBoxDragger, in the clipping group. The geometry of the dragger will also be used for clipping and the results may be unexpected. One exception is if the dragger is configured to use the clipping shape as "proxy" geometry (see SoInteractionKit.setPartAsPath()). A better solution is to put the dragger in the scene graph outside the clipping group, add a transform node to the clipping group and connect the fields of the dragger to the fields of the transform node (see SoField.connectFrom()).

The clipping result is based on the odd-winding rule, so the result is not simply the union or the intersection of the closed surfaces. If the goal is to define a clipping shape which is the result of the intersection/union of multiple closed surfaces, consider using the SoCSGShape node as a child of SoVolumeClippingGroup.

In some cases the number of passes specified may not be enough to clip correctly with the specified geometry. The numPasses field allows you to increase the clipping quality, for example when using shapes with a lot of concavity. To query the maximum allowed number of passes, which depends on your graphics card, use the static method getMaxNumPasses(). The setNotEnoughPassCallback() method allows the application to be notified when numPasses is not sufficient.

Standard clipplanes (see SoClipPlane) affect VolumeViz rendering nodes, but the VolumeViz specific clipping nodes generally provide better performance and allow much more complex clipping. Simple axis-aligned clipping can be done more efficiently using the SoROI node. The SoUniformGridClipping or SoUniformGridProjectionClipping nodes clip against height-field surfaces (e.g. seismic horizons). The SoVolumeMask node clips against a boolean mask volume on a per-voxel basis.

Notes:

When using a custom SoVolumeShader with this node and redefining the main() function, you must call VVizClipVoxel() in the main() function if you are writing a fragment shader. If you don't do this you will get a GLSL compilation error or clipping won't work.

Because this node uses special textures, all texture units between IVVR_FIRST_RESERVED_TEXTURE_UNIT (or SoFragmentShader.getMaxTextureImageUnit()-SoShaderProgram.getNumReservedTextures() if this variable is not set) and :

• IVVR_FIRST_RESERVED_TEXTURE_UNIT-2*numPasses are reserved if GL_EXT_texture_array is not supported.
• IVVR_FIRST_RESERVED_TEXTURE_UNIT-2 are reserved if GL_EXT_texture_array is supported.

SoVolumeClippingGroup requires the following OpenGL extensions. Use the isSupported() static method to check for support on the current graphics board or use the IvReport tool to print a report about the graphics board.

• GL_ARB_depth_texture
• GL_ARB_fragment_program_shadow,
• GL_ARB_framebuffer_object,
• GL_ARB_shading_language_100

Because this node requires closed geometry, clipping planes (SoClipPlane) are automatically disabled when computing the clipping shape.

When used inside an SoOffscreenVolumeRender results might be incorrect. In specific cases geometry might be seen as opened.

EXAMPLE

The following code clips a volume with a cone:

 SoVolumeClippingGroup volClipGroup = new SoVolumeClippingGroup();
   volClipGroup.addChild( new SoCone() );
 
 SoSeparator volSep = new SoSeparator();
   volSep.addChild( volumeData );
   volSep.addChild( transferFunction );
   volSep.addChild( volClipGroup );
   volSep.addChild( volumeRender );
 root.addChild( volSep );

Clipping object	Clipping applied to a volume

File format/default:

VolumeClippingGroup {

numPasses	2
clipOutside	true

}

See also:

SoVolumeRender, SoUniformGridClipping, SoShaderProgram, SoVolumeRenderingQuality, SoVolumeIsosurface, SoCSGShape, SoPreferences

Nested Class Summary

Nested classes/interfaces inherited from class com.openinventor.inventor.Inventor

Inventor.ConstructorCommand

Field Summary

Fields

Modifier and Type	Field and Description
SoSFBool	clipOutside If true, voxels inside the clipping object will be drawn, voxels outside will be clipped.
SoSFInt32	numPasses Number of passes used to do the clipping.

Fields inherited from class com.openinventor.inventor.nodes.SoGroup

boundingBoxIgnoring

Fields inherited from class com.openinventor.inventor.Inventor

VERBOSE_LEVEL, ZeroHandle

Constructor Summary

Constructors

Constructor and Description
SoVolumeClippingGroup() Default constructor.

Method Summary

Modifier and Type	Method and Description
static int	getMaxNumPasses() Calls getMaxNumPasses((com.openinventor.inventor.misc.SoState)null).
static int	getMaxNumPasses(SoState state) Returns the maximum number of passes supported by the hardware.
static boolean	isSupported() Calls isSupported((com.openinventor.inventor.misc.SoState)null).
static boolean	isSupported(SoState state) Indicates if volume clipping is supported by your graphics board.

Methods inherited from class com.openinventor.inventor.nodes.SoGroup

addChild, findChild, getChild, getNumChildren, insertChild, removeAllChildren, removeChild, removeChild, replaceChild, replaceChild

Methods inherited from class com.openinventor.inventor.nodes.SoNode

affectsState, callback, copy, copy, distribute, doAction, getAlternateRep, getBoundingBox, getByName, getMatrix, getPrimitiveCount, getRenderUnitID, GLRender, GLRenderBelowPath, GLRenderInPath, GLRenderOffPath, grabEventsCleanup, grabEventsSetup, handleEvent, isBoundingBoxIgnoring, isOverride, pick, rayPick, search, setOverride, touch, write

Methods inherited from class com.openinventor.inventor.fields.SoFieldContainer

copyFieldValues, copyFieldValues, enableNotify, fieldsAreEqual, get, getAllFields, getEventIn, getEventOut, getField, getFieldName, hasDefaultValues, isNotifyEnabled, set, setToDefaults

Methods inherited from class com.openinventor.inventor.misc.SoBase

dispose, getEXTERNPROTO, getName, getPROTO, isDisposable, isSynchronizable, setName, setSynchronizable

Methods inherited from class com.openinventor.inventor.Inventor

getAddress, getNativeResourceHandle, startInternalThreads, stopInternalThreads

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

numPasses

public final SoSFInt32 numPasses

Number of passes used to do the clipping. Increasing this number increases the image quality but decreases performance. Default is 2 and maximum is SoVolumeClippingGroup.getMaxNumPasses().

clipOutside

public final SoSFBool clipOutside

If true, voxels inside the clipping object will be drawn, voxels outside will be clipped. Default is true. Note that if the VolumeClippingGroup is empty, setting clipOutside to true will clip everything and setting it to false will clip nothing.

Constructor Detail

SoVolumeClippingGroup

public SoVolumeClippingGroup()

Default constructor.

Method Detail

getMaxNumPasses

public static int getMaxNumPasses()

Calls getMaxNumPasses((com.openinventor.inventor.misc.SoState)null).

isSupported

public static boolean isSupported()

Calls isSupported((com.openinventor.inventor.misc.SoState)null).

getMaxNumPasses

public static int getMaxNumPasses(SoState state)

Returns the maximum number of passes supported by the hardware.

isSupported

public static boolean isSupported(SoState state)

Indicates if volume clipping is supported by your graphics board. When using a debug build of Open Inventor, some "no context available" warning messages may be generated. You can ignore them or see SoGLExtension for an example of using SoGLContext to avoid them.