Class SoCircularExtrusion

  • All Implemented Interfaces:

    public class SoCircularExtrusion
    extends SoBaseExtrusion
    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:

    • DEFAULT : Every point in the generated geometry is scaled.
    • SPINE_ONLY : Only the spine points are scaled. The cross section points are not scaled, so the cross section shape is undistorted even is scaling is non-uniform.
    • SECTION_ONLY : Only the cross section points are scaled. Not currently implemented.
    • NONE : SoExtrusion ignores the scaling state. Not currently implemented.

    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

    Open Inventor 8.6 File format/default:

    CircularExtrusion {
      beginCap true
      endCap true
      spine [ 0 0 0, 0 1 0 ]
      scaleMode DEFAULT
      extrusionMode SMOOTH
      radius [ 1 ]
      activeSection [ 0, 1 ]

    See Also:
    SoExtrusion, SoComplexity, SoBaseExtrusion
    • Field Detail

      • radius

        public final SoSFFloat radius
        Radius of the circular cross-section. The default value is 1.
      • activeSection

        public final SoSFVec2f activeSection
        Defines the visible section of the spine in normalized coordinates. The default is (0,1) meaning that the entire spine is rendered.
      • spineSimplificationMode

        public final SoSFEnum<SoCircularExtrusion.SpineSimplificationModes> spineSimplificationMode
        Defines the spine simplification behavior of the extrusion. . 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.
    • Constructor Detail

      • SoCircularExtrusion

        public SoCircularExtrusion()