public class SoVRMLExtrusion extends SoVRMLGeometry
SoVRMLExtrusionnode specifies geometric shapes based on a two-dimensional cross section extruded along a three-dimensional spine. The cross section can be scaled and rotated at each spine point to produce a wide variety of shapes.
<font color="#0000FF">NOTE:</font> This class does not exist in Open Inventor 10.0 and later.
This section describes the expected behavior of the node in a conforming VRML97 browser application. In some cases, the application is responsible for implementing portions of the expected behavior. Open Inventor viewer classes and IVF classes implement some of the application behaviors.
This section may reference portions of the VRML97 specification that are not present in this help file. The complete VRML97 spec is available at
SoVRMLExtrusion node specifies geometric shapes based on a two-dimensional cross section extruded along a three-dimensional spine. The cross section can be scaled and rotated at each spine point to produce a wide variety of shapes.
SoVRMLExtrusion is defined by a 2D
crossSection piecewise linear curve (described as a series of connected vertices), a 3D
spine piecewise linear curve (also described as a series of connected vertices), a list of 2D
scale parameters, and a list of 3D
orientation parameters. Shapes are constructed as follows: The cross-section curve, which starts as a curve in the XZ plane, is first scaled about the origin by the first
scale parameter (first value scales in X, second value scales in Z). It is then rotated about the origin by the first
orientation parameter, and translated by the vector given as the first vertex of the
spine curve. It is then extruded through space along the first segment of the
spine curve. Next, it is scaled and rotated by the second
orientation parameters and extruded by the second segment of the
spine, and so on. The number of
orientation values must equal the number of spine points, or contain one value that is applied to all points. The
scale values must be > 0.
A transformed cross section is found for each joint (that is, at each vertex of the
spine curve, where segments of the extrusion connect), and the joints and segments are connected to form the surface. No check is made for self-penetration. Each transformed cross section is determined as follows:
scalegiven for the current joint.
If the spine curve is closed: The first and last points need to have the same tangent. This tangent is found as above, but using the points
i +1] and
n -2] for
i -1], where
n -2] is the next to last point on the curve. The last point in the curve,
n -1], is the same as the first,
If the spine curve is not closed: The tangent used for the first point is just the direction from
spine, and the tangent used for the last is the direction from
n -2] to
In the simple case where the spine curve is flat in the XY plane, these rotations are all just rotations about the Z axis. In the more general case where the spine curve is any 3D curve, you need to find the destinations for all 3 of the local X, Y, and Z axes so you can completely specify the rotation. The Z axis is found by taking the cross product of:
If the three points are collinear then this value is zero, so take the value from the previous point. Once you have the Z axis (from the cross product) and the Y axis (from the approximate tangent), calculate the X axis as the cross product of the Y and Z axes.
orientationto the cross-section relative to this new plane. Rotate it counterclockwise about the axis and by the angle specified in the
orientationfield at that joint.
Surfaces of revolution: If the cross section is an approximation of a circle and the spine is straight, then the
SoVRMLExtrusion is equivalent to a surface of revolution, where the
scale parameters define the size of the cross section along the spine.
Cookie-cutter extrusions: If the scale is 1, 1 and the spine is straight, then the cross section acts like a cookie cutter, with the thickness of the cookie equal to the length of the spine.
Bend/twist/taper objects: These shapes are the result of using all fields. The spine curve bends the extruded shape defined by the cross section, the orientation parameters twist it around the spine, and the scale parameters taper it (by scaling about the spine).
SoVRMLExtrusion has three parts: the sides , the
beginCap (the surface at the initial end of the spine) and the
endCap (the surface at the final end of the spine). The caps have an associated SFBool field that indicates whether it exists (true) or doesn't exist (false).
endCap fields are specified as true, planar cap surfaces will be generated regardless of whether the
crossSection is a closed curve. (If
crossSection isn't a closed curve, the caps are generated as if it were
crossSection that's equal to the initial point. Note that an open surface can still have a cap, resulting (for a simple case) in a shape something like a soda can sliced in half vertically.) These surfaces are generated even if
spine is also a closed curve. If a field value is false, the corresponding cap is not generated.
SoVRMLExtrusion automatically generates its own normals. Orientation of the normals is determined by the vertex ordering of the triangles generated by
SoVRMLExtrusion. The vertex ordering is in turn determined by the
crossSection curve. If the
crossSection is counterclockwise when viewed from the +Y axis, then the polygons will have counterclockwise ordering when viewed from 'outside' of the shape (and
vice versa for clockwise ordered
Texture coordinates are automatically generated by extrusions. Textures are mapped so that the coordinates range in the U direction from 0 to 1 along the
crossSection curve (with 0 corresponding to the first point in
crossSection and 1 to the last) and in the V direction from 0 to 1 along the
spine curve (again with 0 corresponding to the first listed
spine point and 1 to the last). When
crossSection is closed, the texture has a seam that follows the line traced by the
crossSection's start/end point as it travels along the
spine. If the
beginCap exist, the
crossSection curve is uniformly scaled and translated so that the largest dimension of the cross-section (X or Z) produces texture coordinates that range from 0.0 to 1.0. The
endCap textures' S and T directions correspond to the X and Z directions in which the
crossSection coordinates are defined.
NOTE: If your extrusion appears to twist unexpectedly, try setting environment variable OIV_EXTRUSION_EPSILON to a value slightly smaller number than the default, which is .998.
|crossSection||[ 1 1, 1 -1, -1 -1, -1 1, 1 1 ]|
|orientation||0 0 1 0|
|spine||[ 0 0 0, 0 1 0 ]|
|Modifier and Type||Field and Description|
The surface at the initial end of the spine.
Indicates whether the vertices are ordered in a counterclockwise direction when viewed from the outside (true) or in a clockwise direction (false).
Indicates whether faces of a shape are convex (true).
Indicates the minimum angle (in radians) between two adjacent face normals required to form a sharp crease at the edge when default normals are computed and used.
A 2D crossSection piecewise linear curve (described as a series of connected vertices);.
The surface at the final end of the spine.
The orientation of the crossSection at each spine point.
The scale factor of the crossSection at each spine point.
If you know that the shape encloses a volume, set this value to true.
A 3D spine piecewise linear curve (also described as a series of connected vertices);.
boundingBoxIgnoring, LINES, POINTS, POLYGONS, TEXT
|Constructor and Description|
getShapeType, isPrimitiveRestartAvailable, isPrimitiveRestartAvailable
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
copyFieldValues, copyFieldValues, enableNotify, fieldsAreEqual, get, getAllFields, getEventIn, getEventOut, getField, getFieldName, hasDefaultValues, isNotifyEnabled, set, setToDefaults
dispose, getEXTERNPROTO, getName, getPROTO, isDisposable, isSynchronizable, setName, setSynchronizable
getAddress, getNativeResourceHandle, startInternalThreads, stopInternalThreads
public final SoSFBool beginCap
public final SoSFBool ccw
public final SoSFBool solid
public final SoSFBool convex
public final SoSFFloat creaseAngle
public final SoMFVec2f crossSection
public final SoSFBool endCap
public final SoMFRotation orientation
public final SoMFVec2f scale
public final SoMFVec3f spine
Generated on March 25, 2020, Copyright © Thermo Fisher Scientific. All rights reserved. http://www.openinventor.com