SoDepthOffset Class Reference
[Properties]

VSG extension Property node that applies a depth offset. More...

#include <Inventor/nodes/SoDepthOffset.h>

Inheritance diagram for SoDepthOffset:
SoNode SoFieldContainer SoBase SoRefCounter SoTypedObject

List of all members.

Public Member Functions

virtual SoType getTypeId () const
 SoDepthOffset ()

Static Public Member Functions

static SoType getClassTypeId ()

Public Attributes

SoSFFloat offset
SoSFBool on

Detailed Description

VSG extension Property node that applies a depth offset.

This node can be used to offset shapes that are co-planar, in order to resolve depth buffer artifacts, commonly called z-buffer "stitching".

The effect is similar to SoPolygonOffset but this node uses a different algorithm (based on Lengyel's method from Game Programming Gems and improved by VSG) in which the projection matrix is modified to offset subsequent geometry. As a result it has advantages over SoPolygonOffset in some cases. Specifically, SoDepthOffset applies its offset value to all types of geometry, not just polygons, and does not require any additional per-vertex calculations on the GPU.

The offset value is accumulated in the traversal state. For example:

depthOffsetState.png

Note that if the accumulation of offset values during the traversal is greater than 1, the accumulated offset value is normalized so that, in this case, the offset values are not absolute but relative to each other.

SoDepthOffset has two limitations. First, since it modifies the projection matrix during traversal, it may prevent building a render cache for part of the scene graph. Second, the offset does not take into account the depth slope of the geometry (as SoPolygonOffset does), so a larger offset may be required for geometry that is not perpendicular to the view vector (facing the camera).

The presence of a SoDepthOffset node in the scene graph causes depth buffer values to be different, even if 'offset' is equal to 0.

The render caching issue is easily handled, by adjusting your scene graph structure, just as you would for any non-cacheable node, to ensure that the actual shape nodes are cached even if the parent group node cannot cache:
For example, using this scene graph structure:

depthOffsetCache.png

instead of this one:

depthOffsetNoCache.png

FILE FORMAT/DEFAULT

ACTION BEHAVIOR

SEE ALSO

SoPolygonOffset, SoDepthBuffer

See related examples:

DepthBuffer, DepthOffset, PolygonOffset, CellShapeConnectedFromSkin


Constructor & Destructor Documentation

SoDepthOffset::SoDepthOffset (  ) 

Constructor.


Member Function Documentation

static SoType SoDepthOffset::getClassTypeId (  )  [static]

Returns the type identifier for this class.

Reimplemented from SoNode.

virtual SoType SoDepthOffset::getTypeId (  )  const [virtual]

Returns the type identifier for this specific instance.

Reimplemented from SoNode.


Member Data Documentation

Offset to apply to the projection matrix.


Positive values move geometry toward the camera (the opposite of SoPolygonOffset). Offset value must be in the range [-0.5 .. 0.5] (normalized depth coordinates). Default is 0.001

Enables depth offset. NOTE: field available since Open Inventor 8.1


The documentation for this class was generated from the following file:

Open Inventor Toolkit reference manual, generated on 28 Oct 2019
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