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SoShapeHints Class Reference

The SoShapeHints class is a node containing hints about how to render geometry. More...

#include <Inventor/nodes/SoShapeHints.h>

Inheritance diagram for SoShapeHints::

List of all members.

Public Types
enum	VertexOrdering { UNKNOWN_ORDERING = SoShapeHintsElement::UNKNOWN_ORDERING, CLOCKWISE = SoShapeHintsElement::CLOCKWISE, COUNTERCLOCKWISE = SoShapeHintsElement::COUNTERCLOCKWISE }
enum	ShapeType { UNKNOWN_SHAPE_TYPE = SoShapeHintsElement::UNKNOWN_SHAPE_TYPE, SOLID = SoShapeHintsElement::SOLID }
enum	FaceType { UNKNOWN_FACE_TYPE = SoShapeHintsElement::UNKNOWN_FACE_TYPE, CONVEX = SoShapeHintsElement::CONVEX }
Public Methods
	SoShapeHints (void)
virtual void	doAction (SoAction *action)
virtual void	GLRender (SoGLRenderAction *action)
virtual void	callback (SoCallbackAction *action)
virtual void	getBoundingBox (SoGetBoundingBoxAction *action)
virtual void	pick (SoPickAction *action)
Static Public Methods
void	initClass (void)
Public Attributes
SoSFEnum	vertexOrdering
SoSFEnum	shapeType
SoSFEnum	faceType
SoSFFloat	creaseAngle
Protected Methods
virtual	~SoShapeHints ()

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Detailed Description

The SoShapeHints class is a node containing hints about how to render geometry.

The SoShapeHints node is used to set up clues to the rendering subsystem about how particular aspects of the subsequent geometry in the scene graph should be drawn.

The default settings of the rendering system is tuned towards programmer convenience. For instance, the default is to render both sides of all polygons to make sure we avoid any "holes" in the geometry if the vertex ordering should happen to differ for different polygons.

If the programmer gives up some of this convenience and uses SoShapeHints nodes to more closely specify information about the scene graph geometry, the clues given by the SoShapeHints node(s) will then be used by the rendering subsystem to avoid certain costly operations. Significant gains in rendering speed could be seen as a result.

Be aware that the way backface culling and two-sided lighting is decided by the rendering system is not at all intuitive. Here are the common rules of how primitive shapes will render themselves with regard to how the SoShapeHints::vertexOrdering and SoShapeHints::shapeType fields are set:

• vertexOrdering == CLOCKWISE | COUNTERCLOCKWISE, shapeType == SOLID: causes primitives to be backface culled and rendered with one-sided lighting.

• vertexOrdering == CLOCKWISE | COUNTERCLOCKWISE, shapeType == UNKNOWN_SHAPE_TYPE: primitives are not backface culled and rendered with two-sided lighting.

• vertexOrdering == UNKNOWN_ORDERING, any shapeType: primitives are not backface culled and rendered with one-sided lighting.

(We find this strategy quite odd. It seems more sensible behavior that when vertexordering is unknown, two-sided lighting should be enabled, since it will be difficult to know if a normal points in or out of a polygon. But for compatibility reasons we are of course sticking to the same behavior as the Inventor library.)

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Member Enumeration Documentation

enum SoShapeHints::VertexOrdering

Enumeration of available ways to specify ordering of vertices for a polygon. Enumeration values: UNKNOWN_ORDERING   Ordering not known, render both sides of the polygon. CLOCKWISE   Vertices are specified in a clockwise order. COUNTERCLOCKWISE   Vertices are specified in a counter-clockwise order.

enum SoShapeHints::ShapeType

Enumeration of different shape types. Enumeration values: UNKNOWN_SHAPE_TYPE   Nothing known about the shape, be conservative when rendering. SOLID   The subsequent shapes in the graph are all known to be completely "closed", solid 3D shapes.

enum SoShapeHints::FaceType

Enumeration of polygon face types. Enumeration values: UNKNOWN_FACE_TYPE   Nothing known about subsequent polygon data, be conservative when rendering. CONVEX   Subsequent faces are all convex, so turn off the check for and tesselation of inconvex faces.

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Constructor & Destructor Documentation

SoShapeHints::SoShapeHints (  void )

Constructor.

SoShapeHints::~SoShapeHints (  )  [protected, virtual]

Destructor.

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Member Function Documentation

void SoShapeHints::initClass (  void )  [static]

Sets up initialization for data common to all instances of this class, like submitting necessary information to the Coin type system. Reimplemented from SoNode.

void SoShapeHints::doAction (  SoAction * action )  [virtual]

This function performs the typical operation of a node for any action. Reimplemented from SoNode.

void SoShapeHints::GLRender (  SoGLRenderAction * action )  [virtual]

Action method for the SoGLRenderAction. This is called during rendering traversals. Nodes influencing the rendering state in any way or who wants to throw geometry primitives at OpenGL overrides this method. Reimplemented from SoNode.

void SoShapeHints::callback (  SoCallbackAction * action )  [virtual]

Action method for SoCallbackAction. Simply updates the state according to how the node behaves for the render action, so the application programmer can use the SoCallbackAction for extracting information about the scene graph. Reimplemented from SoNode.

void SoShapeHints::getBoundingBox (  SoGetBoundingBoxAction * action )  [virtual]

Action method for the SoGetBoundingBoxAction. Calculates bounding box and center coordinates for node and modifies the values of the action to encompass the bounding box for this node and to shift the center point for the scene more towards the one for this node. Nodes influencing how geometry nodes calculates their bounding box also overrides this method to change the relevant state variables. Reimplemented from SoNode.

void SoShapeHints::pick (  SoPickAction * action )  [virtual]

Action method for SoPickAction. Does common processing for SoPickAction action instances. Reimplemented from SoNode.

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Member Data Documentation

SoSFEnum SoShapeHints::vertexOrdering

Specifies how vertices are ordered for polygon faces. Set this field to SoShapeHints::CLOCKWISE or SoShapeHints::COUNTERCLOCKWISE if possible to turn on backface culling and thereby optimize rendering. Default value is SoShapeHints::UNKNOWN_ORDERING.

SoSFEnum SoShapeHints::shapeType

Hint about whether or not shapes are known to be "closed". Default value is SoShapeHints::UNKNOWN_SHAPE_TYPE.

SoSFEnum SoShapeHints::faceType

Hint about whether or not polygon faces are known to be convex. Default value is SoShapeHints::CONVEX.

SoSFFloat SoShapeHints::creaseAngle

When normals are automatically generated by Coin (i.e. SoNormal nodes are not used), this is the smallest angle between two faces where we would still calculate normals to do flatshading. If the angle between the normals of two neighboring faces is less than the value of this field, the faces will be smoothshaded around their common edge.

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The documentation for this class was generated from the following files:

• SoShapeHints.cpp
• SoShapeHints.h

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