public class SoExtrusion extends SoBaseExtrusion
SoExtrusionnode 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.
SoExtrusion is defined by:
orientationvalues, The cross-section 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 cross-section 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 cross-section 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 cross-section is then connected to the following instance.
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:
SoExtrusionignores 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 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
SoExtrusion 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).
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).
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
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.
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.
|spine||[ 0 0 0, 0 1 0 ]|
|crossSection||[ 1 1, 1 -1, -1 -1, -1 1, 1 1 ]|
|orientation||0 0 1 0|
|Modifier and Type||Field and Description|
The shape that will be extruded, defined by a 2D piecewise linear curve in the XZ plane (described as a series of connected vertices).
The cross-section 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 cross-section curve.
The cross-section 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
|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 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