SoShapeHints

InventorModule

genre	InventorNodesAutomatic
author	Silicon Graphics Inc
package	MeVisLab/Standard
definition	inventor.def

Purpose

By default, Inventor assumes very little about the shapes it renders. You can use the SoShapeHints node to indicate that vertex-based shapes are solid, contain ordered vertices, or contain convex faces. For fastest rendering, specify SOLID, COUNTERCLOCKWISE, CONVEX shapes.

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.

The SoShapeHints node also affects how default normals are generated. When a node derived from SoVertexShape has to generate default normals, it uses the Crease Angle 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 Crease Angle is 0 (the default), producing one normal per facet. A Crease Angle of PI produces one averaged normal per vertex.

Windows

Default Panel

Output Fields

self

name: self, type: SoNode

Parameter Fields

Field Index

Crease Angle: Float

Face Type: Enum

Shape Type: Enum

Use VBO: Bool

Vertex Ordering: Enum

Visible Fields

Vertex Ordering

name: vertexOrdering, type: Enum, default: UNKNOWN_ORDERING

Indicates how the vertices of faces are ordered. CLOCKWISE 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).

Values:

Title	Name	Description
Unknown Ordering	UNKNOWN_ORDERING	Ordering of vertices is unknown.
Clockwise	CLOCKWISE	Face vertices are ordered clockwise (from the outside).
Counterclockwise	COUNTERCLOCKWISE	Face vertices are ordered counterclockwise (from the outside).

Shape Type

name: shapeType, type: Enum, default: UNKNOWN_SHAPE_TYPE

Indicates whether the shape is known to enclose a volume (SOLID) 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.

Values:

Title	Name	Description
Unknown Shape Type	UNKNOWN_SHAPE_TYPE	Unknown shape type.
Solid	SOLID	Solid shape type.

Face Type

name: faceType, type: Enum, default: CONVEX

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 UNKNOWN_FACE_TYPE.

Values:

Title	Name	Description
Unknown Face Type	UNKNOWN_FACE_TYPE	Nothing is known about faces.
Convex	CONVEX	All faces are convex.

Crease Angle

name: creaseAngle, type: Float, default: 0

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.

Use VBO

name: useVBO, type: Bool, default: TRUE