public class SoShapeHints extends SoNode
SoShapeHints
node to indicate that vertex-based shapes (those derived from SoVertexShape
) are solid, contain ordered vertices, or contain convex faces. For fastest rendering, specify SOLID, COUNTERCLOCKWISE, CONVEX shapes.
These hints allow Open Inventor to optimize certain rendering features. Optimizations that may be performed include enabling back-face culling and disabling two-sided lighting. For example, if an object is solid and has ordered vertices, Open Inventor turns on backface culling and turns off two-sided lighting. If the object is not solid but has ordered vertices, it turns off backface culling and turns on two-sided lighting. In all other cases, both backface culling and two-sided lighting are off.
Summary:
vertexOrdering
to COUNTERCLOCKWISE (usually) or CLOCKWISE.
shapeType
to SOLID.
Note: Two-sided lighting is automatically enabled for VolumeViz "slice" primitives, such as SoOrthoSlice
and SoVolumeSkin
.
This node allows the creation of polygons with holes. See the windingType
field description, SoIndexedFaceSet
, and SoFaceSet
for details.
The SoShapeHints
node also affects how default normals are generated. When a node derived from SoVertexShape
has to generate default normals, it uses the creaseAngle
field to determine which edges should be smooth-shaded and which ones should have a sharp crease. The crease angle is the angle between surface normals on adjacent polygons. For example, a crease angle of .5 radians means that an edge between two adjacent polygonal faces will be smooth shaded if the normals to the two faces form an angle that is less than .5 radians (about 30 degrees). Otherwise, it will be faceted.
creaseAngle = 0 | creaseAngle = 0.5 | creaseAngle = PI |
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Normal averaging |
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creaseAngle
is 0 (the default), producing one normal per facet. However, if a vertex is shared by two (or more) faces that should be faceted, the result of normal generation will be multiple normal vectors (one for each face) associated with that vertex. This is in conflict with using OpenGL Vertex Buffer Objects (VBO), which usually provide the best performance. VBO rendering only allows per-vertex (not per-face) normal vectors and only one normal vector per vertex. Some high-level shapes, like SoIndexedFaceSet
, will automatically reorganize the geometry data to produce the requested appearance and still use VBOs for rendering. Lower level shapes like SoBufferedShape
will ignore the creaseAngle field and compute normals using a crease angle of Pi in order to use VBOs for rendering. A creaseAngle
of Pi produces one averaged normal per vertex.
See SoVertexShape
for more information about Vertex Buffer Objects and shape rendering.
File format/default:
ShapeHints {
vertexOrdering | UNKNOWN_ORDERING |
shapeType | UNKNOWN_SHAPE_TYPE |
faceType | CONVEX |
windingType | NO_WINDING_TYPE |
creaseAngle | 0 |
neighborTolerance | 1e-6 |
useVBO | true |
Action behavior:
SoGLRenderAction
, SoCallbackAction
, SoRayPickAction
, SoGetBoundingBoxAction
Sets the state to contain the hints; sets up optimizations based on the hints. Sets: SoShapeHintsElement
, SoCreaseAngleElement
, SoNeighborToleranceElement
See also:
Modifier and Type | Class and Description |
---|---|
static class |
SoShapeHints.FaceTypes
Hints about faces of shape: if all faces are known to be convex or not.
|
static class |
SoShapeHints.ShapeTypes
Hints about entire shape: if shape is known to be a solid object, as opposed to a surface.
|
static class |
SoShapeHints.VertexOrderings
Hints about ordering of face vertices: if ordering of all vertices of all faces is known to be consistent when viewed from "outside" shape or not.
|
static class |
SoShapeHints.WindingTypes
Winding type possible values.
|
SoNode.RenderModes
Inventor.ConstructorCommand
Modifier and Type | Field and Description |
---|---|
SoSFFloat |
creaseAngle
Indicates the minimum angle (in radians) between two adjacent face normals required to form a sharp crease at the edge when normal vectors are computed automatically by Open Inventor.
|
SoSFEnum<SoShapeHints.FaceTypes> |
faceType
Indicates whether each face is convex.
|
SoSFFloat |
neighborTolerance
Specifies the tolerance value to use when default normals are computed.
|
SoSFEnum<SoShapeHints.ShapeTypes> |
shapeType
Indicates whether the shape is known to enclose a volume (SOLID) or not.
|
SoSFBool |
useVBO
This field controls whether subsequent shapes in the scene graph can use OpenGL Vertex Buffer Objects (VBO) to speed up rendering.
|
SoSFEnum<SoShapeHints.VertexOrderings> |
vertexOrdering
Indicates how the vertices of faces are ordered.
|
SoSFEnum<SoShapeHints.WindingTypes> |
windingType
Indicates the winding rule used to define holes in a polygon.
|
VERBOSE_LEVEL, ZeroHandle
Constructor and Description |
---|
SoShapeHints()
Creates a shape hints node with default settings.
|
Modifier and Type | Method and Description |
---|---|
static boolean |
isVBOSupported()
Indicates if Vertex Buffer Object (VBO) is supported by your graphics board.
|
affectsState, callback, copy, copy, distribute, doAction, getAlternateRep, getBoundingBox, getByName, getMatrix, getPrimitiveCount, getRenderEngineMode, 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, getName, isDisposable, isSynchronizable, setName, setSynchronizable
getNativeResourceHandle
public final SoSFEnum<SoShapeHints.VertexOrderings> vertexOrdering
VertexOrdering
. Default is UNKNOWN_ORDERING.public final SoSFEnum<SoShapeHints.ShapeTypes> shapeType
ShapeType
. Default is UNKNOWN_SHAPE_TYPE.public final SoSFEnum<SoShapeHints.FaceTypes> faceType
FaceType
. Default is CONVEX.public final SoSFEnum<SoShapeHints.WindingTypes> windingType
SoIndexedFaceSet
and SoFaceSet
to determine which parts of the polygon are on the interior and which are on the exterior and should not be filled. By default this field value is NO_WINDING_TYPE, that is, no winding rules are used, so there are no holes. Use enum WindingType
.
For a single contour, the winding number of a point is the signed number of revolutions we make around that point while traveling once around the contour (where a counterclockwise revolution is positive and a clockwise revolution is negative). When there are several contours, the individual winding numbers are summed. This procedure associates a signed integer value with each point in the plane. Note that the winding number is the same for all points in a single region.
The following figure shows three sets of contours and winding numbers for points inside those contours. In the left set, all three contours are counterclockwise, so each nested interior region adds one to the winding number. For the middle set, the two interior contours are drawn clockwise, so the winding number decreases and actually becomes negative.
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NOTE: In LINES drawing style (see SoDrawStyle
), if windingType
is not NO_WINDING_TYPE, or if faceType
is UNKNOWN_FACE_TYPE, the edges of the tessellated triangles will be drawn.
public final SoSFBool useVBO
SoPreferences
).
In most cases there is no reason to set this field. Open Inventor will automatically choose the best rendering strategy. For example, VBOs generally provide the best performance for large shapes (many vertices), but not necessarily for small shapes. In specific cases it may be useful to influence these decisions using this field and/or the related environment variables including OIV_MIN_VERTEX_VBO and OIV_MIN_VERTEX_VAVBO_NOCACHE. See SoVertexShape
for more discussion about shape rendering strategy.
public final SoSFFloat creaseAngle
public final SoSFFloat neighborTolerance
Specifically it determines which (other) points in the shape are close enough to influence the normal at each vertex. Setting a smaller tolerance value will select a smaller number of points and can reduce the time required for computing normals on very large, very dense geometry.
If the OIV_NORMGEN_TOLERANCE environment variable is set, the default is 1/OIV_NORMGEN_TOLERANCE.
Generated on July 31, 2019, Copyright © Thermo Fisher Scientific. All rights reserved. http://www.openinventor.com