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NAME SoShapeHints SoShapeHints "" { node that provides hints about shapes }
INCLUDE nodes/SoShapeHints.h
DESC {
By default, Inventor assumes very little about the shapes it renders.
You can use the \cSoShapeHints\. node to indicate that vertex-based
shapes (those derived from \cSoVertexShape\.) are solid, contain
ordered vertices, or contain convex faces. For fastest rendering,
specify SOLID, COUNTERCLOCKWISE, CONVEX shapes.
\p
These hints allow 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, 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.
\p
The \cSoShapeHints\. node also affects how default normals are
generated. When a node derived from \cSoVertexShape\. has to generate
default normals, it uses the \vcreaseAngle\. 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. Normal generation is fastest when the creaseAngle is 0
(the default), producing one normal per facet. A creaseAngle of pi
produces one averaged normal per vertex.
}
ENUM VertexOrdering {
UNKNOWN_ORDERING "Ordering of vertices is unknown",
CLOCKWISE "Face vertices are ordered clockwise
(from the outside)",
COUNTERCLOCKWISE "Face vertices are ordered counterclockwise
(from the outside)"
}
ENUM ShapeType {
UNKNOWN_SHAPE_TYPE "Nothing is known about the shape",
SOLID "The shape encloses a volume"
}
ENUM FaceType {
UNKNOWN_FACE_TYPE "Nothing is known about faces",
CONVEX "All faces are convex"
}
FIELD vertexOrdering {
Indicates how the vertices of faces are ordered. \kCLOCKWISE\.
ordering means that the vertices of each face form a clockwise loop
around the face, when viewed from the outside (the side toward which
the normal points).
}
FIELD shapeType {
Indicates whether the shape is known to enclose a volume (\kSOLID\.)
or not. If the inside (the side away from the surface normal) of any
part of the shape is visible, the shape is not solid.
}
FIELD faceType {
Indicates whether each face is convex. Because the penalty for
non-convex faces is very steep (faces must be triangulated
expensively), the default assumes all faces are convex. Therefore,
shapes with concave faces may not be displayed correctly unless this
hint is set to \kUNKNOWN_FACE_TYPE\..
}
FIELD creaseAngle {
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.
}
METHOD "" SoShapeHints() {
Creates a shape hints node with default settings.
}
METHOD "" static SoType getClassTypeId() {
Returns type identifier for this class.
}
ACTION SoGLRenderAction, SoCallbackAction, SoRayPickAction,
SoGetBoundingBoxAction {
Sets the state to contain the hints; sets up optimizations based on
the hints.
}
ALSO { SoVertexShape }
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