public class SoExtrusion extends SoBaseExtrusion
SoExtrusion
node specifies geometric shapes based on a twodimensional cross section extruded along a threedimensional spine. The cross section can be scaled and rotated at each spine point to produce a wide variety of shapes.
An SoExtrusion
is defined by:
crossSection
spine
SoBaseExtrusion
.
scale
values orientation
values, The crosssection curve is rotated by this value relative to a local reference system with origin at the current spine point and X / Z axes in the plane containing the crosssection curve. If one value is specified it applies to every spine point, else there should be as many values as there are points in the spine.
Shapes are constructed as follows  For each point in the spine, the crosssection curve, which is a curve in the XZ plane, is scaled about the origin by the corresponding scale
parameter (first value scales in X, second value scales in Z), rotated about the origin by the corresponding orientation
parameter and translated by the vector defined by the corresponding vertex of the spine
curve. Each instance of the crosssection is then connected to the following instance.
The scaleMode
field 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:
SoExtrusion
ignores the scaling state. Not currently implemented.
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 selfpenetration. Each transformed cross section is determined as follows:
scale
given for the current joint.
For all points other than the first or last: The tangent for spine
[
i ] is found by normalizing the vector defined by (spine
[
i +1]  spine
[
i 1]).
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 spine
[0] for spine
[
i ], spine
[1] for spine
[
i +1] and spine
[
n 2] for spine
[
i 1], where spine
[
n 2] is the next to last point on the curve. The last point in the curve, spine
[
n 1], is the same as the first, spine
[0].
If the spine curve is not closed: The tangent used for the first point is just the direction from spine
[0] to spine
[1], and the tangent used for the last is the direction from spine
[
n 2] to spine
[
n 1].
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:
(spine
[
i 1]  spine
[
i ]) and (spine
[
i +1]  spine
[
i ]).
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.
orientation
to the crosssection relative to this new plane. Rotate it counterclockwise about the axis and by the angle specified in the orientation
field at that joint.
spine
point.
Surfaces of revolution: If the cross section is an approximation of a circle and the spine is straight, then the SoExtrusion
is equivalent to a surface of revolution, where the scale
parameters define the size of the cross section along the spine.
Cookiecutter 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).
SoExtrusion
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).
When the beginCap
or 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.
SoExtrusion
automatically generates its own normals. Orientation of the normals is determined by the vertex ordering of the quads generated by SoExtrusion
. 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 crossSection
curves).
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 endCap
and/or beginCap
exist, the crossSection
curve is uniformly scaled and translated so that the largest dimension of the crosssection (X or Z) produces texture coordinates that range from 0.0 to 1.0. The beginCap
and endCap
textures' S and T directions correspond to the X and Z directions in which the crossSection
coordinates are defined.
Also 3D texture coordinates are automatically generated, in a similar way to 2D textures.
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.
NOTE: If your crossSection
is not convex, you must use a SoShapeHints
and set the faceType field to UNKNOWN_FACE_TYPE.
File format/default:
Extrusion {
beginCap  true 
endCap  true 
spine  [ 0 0 0, 0 1 0 ] 
scaleMode  DEFAULT 
crossSection  [ 1 1, 1 1, 1 1, 1 1, 1 1 ] 
orientation  0 0 1 0 
scale  1 1 
See also:
SoBaseExtrusion.ExtrusionModes, SoBaseExtrusion.ScaleModes
SoShape.ShapeTypes
Inventor.ConstructorCommand
Modifier and Type  Field and Description 

SoMFVec2f 
crossSection
The shape that will be extruded, defined by a 2D piecewise linear curve in the XZ plane (described as a series of connected vertices).

SoMFRotation 
orientation
The crosssection curve is rotated by this value relative to a local reference system with origin at the current spine point and X / Z axes in the plane containing the crosssection curve.

SoMFVec2f 
scale
The crosssection curve is scaled by this value on the X and Z axes.

BASIC, beginCap, DEFAULT, endCap, extrusionMode, NONE, scaleMode, SECTION_ONLY, SMOOTH, SMOOTH_WITHOUT_SELF_INTERSECTIONS, spine, SPINE_ONLY
boundingBoxIgnoring, LINES, POINTS, POLYGONS, TEXT
VERBOSE_LEVEL, ZeroHandle
Constructor and Description 

SoExtrusion()
Constructor.

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 SoMFVec2f crossSection
public final SoMFRotation orientation
public final SoMFVec2f scale
Generated on January 29, 2020, Copyright © Thermo Fisher Scientific. All rights reserved. http://www.openinventor.com