SoCircularExtrusion Class Reference

VSG extension Geometric shape formed by extruding a circle along a 3D spine. More...

#include <Inventor/nodes/SoCircularExtrusion.h>

Inheritance diagram for SoCircularExtrusion:
SoBaseExtrusion SoShape SoNode SoFieldContainer SoBase SoRefCounter SoTypedObject

List of all members.

Public Types

enum  SpineSimplificationMode {

Public Member Functions

virtual SoType getTypeId () const
 SoCircularExtrusion ()

Static Public Member Functions

static SoType getClassTypeId ()

Public Attributes

SoSFFloat radius
SoSFVec2f activeSection
SoSFEnum spineSimplificationMode

Detailed Description

VSG extension Geometric shape formed by extruding a circle along a 3D spine.

The SoCircularExtrusion node is a geometric shape based on a constant radius circle cross section extruded along a three-dimensional polyline (spine). The circle center lies on the spine and the circle lies on the plane normal to the spine at each point. This is similar to specifying an SoExtrusion with a circle cross-section, which is convenient for many applications, but this node has additional advantages because it responds to the SoComplexity value.

The application can specify which caps are created using the fields beginCap and endCap. By default both caps are visible.

The application can specify the visible portion of the shape along the spine using normalized curvilinear coordinates (activeSection). By default the entire spine is visible.

The SoCircularExtrusion representation is dependent on SoComplexity::value. The shape is always simplified when the SoComplexity value is less than 1. Both the cross section (number of segments used for the circle) and the spine (number of points used for the spine) are affected by the simplification. The simplification algorithm approximates the spine by taking into account its curvature. The cross section circle is approximated by at least 10 points. With a SoComplexity value of 0 the extruded shape has the roughest representation.

Approximately the same geometry could be defined using an SoExtrusion node, but that node does not currently respond the SoComplexity value. Likewise the clipping behavior could be obtained using two SoClipPlane nodes, but SoCircularExtrusion uses less memory when the activeSection is a subset of the full spine. These two features make SoCircularExtrusion valuable when a large number of cylindrical objects must be displayed.

The scaleMode field (inherited from SoBaseExtrusion) is used to select the points that will be scaled by the current transformation (for example SoTransform), if any. Translation and rotation are applied in all cases. The options are:

The extrusionMode field (inherited from SoBaseExtrusion) is used to select the extrusion algorithm.

The spine polyline segments must be C0 continous, that is, the spine must be connected at joints. The following segments may be C1 discontinous but be aware that very narrow angles between consecutive polyline semgments can produce odd results with SMOOTH extrusionMode modes. This is especially noticeable when the angles between segments are very small with respect to the radius. In the following images the consecutive points A, B, C in the spine show one of these cases. The problem is at point B whose cross sections are abnormally large.

Spine Wireframe Shaded
NOTE: node available since Open Inventor 8.6



SoExtrusion, SoComplexity, SoBaseExtrusion

See related examples:

MedicalVolumePipeClipping, VolumePipeClipping

Member Enumeration Documentation


The spine simplification is done based only on geometric data.

This is sufficient if there is a single material applied to the entire extrusion, but may produce incorrect results if multiple materials are applied.


The spine simplification is done preserving the materials applied to the spine.

Constructor & Destructor Documentation

SoCircularExtrusion::SoCircularExtrusion (  ) 


Member Function Documentation

static SoType SoCircularExtrusion::getClassTypeId (  )  [static]

Returns the type identifier for this class.

Reimplemented from SoBaseExtrusion.

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

Returns the type identifier for this specific instance.

Reimplemented from SoBaseExtrusion.

Member Data Documentation

Defines the visible section of the spine in normalized coordinates.

The default is (0,1) meaning that the entire spine is rendered.

Radius of the circular cross-section.

The default value is 1.

Defines the spine simplification behavior of the extrusion.

Use enum SpineSimplificationMode. Default is DEFAULT. DEFAULT means spine simplification depends only on geometry. This is appropriate in the typical case where a single material is applied to the entire extrusion. RESPECT_MATERIALS means spine simplification preserves multiple materials (if any) applied to the extrusion. This could reduce rendering performance.

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

Open Inventor Toolkit reference manual, generated on 25 Feb 2021
Copyright © Thermo Fisher Scientific All rights reserved.