SoShapeHints - Online Linux Manual PageSection : 3
Updated : Mon Jan 25 2021
Source : Version 2.5.0
Note : Coin
NAMESoShapeHints − The SoShapeHints class is a node containing hints about how to render geometry.
SYNOPSIS
#include <Inventor/nodes/SoShapeHints.h> Inherits SoNode.
Public Typesenum 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 Member Functionsvirtual SoType getTypeId (void) const
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 Member Functionsstatic SoType getClassTypeId (void)
static void initClass (void)
Public AttributesSoSFEnum vertexOrdering
SoSFEnum shapeType
SoSFEnum faceType
SoSFFloat creaseAngle
Protected Member Functionsvirtual const SoFieldData * getFieldData (void) const
virtual ~SoShapeHints ()
Static Protected Member Functionsstatic const SoFieldData ** getFieldDataPtr (void)
Additional Inherited Members
Detailed DescriptionThe 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 or COUNTERCLOCKWISE, shapeType == SOLID: causes primitives to be backface culled and rendered with one-sided lighting. • vertexOrdering == CLOCKWISE or COUNTERCLOCKWISE, shapeType == UNKNOWN_SHAPE_TYPE: primitives are not backface culled, and they are rendered with two-sided lighting. • vertexOrdering == UNKNOWN_ORDERING, any shapeType: primitives are not backface culled, and they are rendered with one-sided lighting. The OpenGL vertex ordering will be set to counter clockwise ordering. The UNKNOWN_ORDERING enum has a special and non-intuitive meaning. The ordering is really set to counter clockwise -- in OpenGL and when generating normals. However, if you want to render your geometry with one-sided lighting and backface culling disabled, you have to use this enum value, and your polygons need to be in counter clockwise ordering. FILE FORMAT/DEFAULTS: ShapeHints {
vertexOrdering UNKNOWN_ORDERING
shapeType UNKNOWN_SHAPE_TYPE
faceType CONVEX
creaseAngle 0
}
Member Enumeration Documentation
enum SoShapeHints::VertexOrderingEnumeration of available ways to specify ordering of vertices for a polygon. Enumerator 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::ShapeTypeEnumeration of different shape types. Enumerator 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. Backface culling will be done if vertexOrdering is known.
enum SoShapeHints::FaceTypeEnumeration of polygon face types. Enumerator UNKNOWN_FACE_TYPE Signifies: nothing is known about subsequent polygon data, be conservative when rendering. All polygons in the scene will be analyzed to see if they needs to be tessellated (broken up) into triangles before passed on to the underlying immediate mode rendering system. The OpenGL rendering system handles most complex polygon types, but not all: it can for instance have problems with many-sided, concave polygons (concave polygons are 'hollow', that is: rounded inwards). Coin's internal tessellator will most often handle the cases that OpenGL fails on. So if you are seeing weird artifacts in how complex polygons are rendered, try to change the SoShapeHints::faceType field to this value and see if they are then rendered correctly. Beware that turning on this functionality might have the effect of making the rendering performance worse. If it has a noticable effect on your particular scenegraph, we advise that you investigate whether you could change how the polygons are generated for Coin rendering and then avoid using this flag. CONVEX Subsequent faces are all convex, so turn off the check for and tessellation of inconvex faces. Subsequent polygons from faceset-type nodes (like SoFaceSet and SoIndexedFaceSet) will be sent unmodified to OpenGL, thereby assuming that the polygons are in a form handled by OpenGL.
Constructor & Destructor Documentation
SoShapeHints::SoShapeHints (void)Constructor. References CLOCKWISE, CONVEX, COUNTERCLOCKWISE, creaseAngle, faceType, shapeType, SOLID, UNKNOWN_FACE_TYPE, UNKNOWN_ORDERING, UNKNOWN_SHAPE_TYPE, and vertexOrdering.
SoShapeHints::~SoShapeHints () [protected], [virtual]Destructor.
Member Function Documentation
SoType SoShapeHints::getTypeId (void) const [virtual]Returns the type identification of an object derived from a class inheriting SoBase. This is used for run-time type checking and 'downward' casting. Usage example: void foo(SoNode * node)
{
if (node->getTypeId() == SoFile::getClassTypeId()) {
SoFile * filenode = (SoFile *)node; // safe downward cast, knows the type
}
else if (node->getTypeId().isOfType(SoGroup::getClassTypeId())) {
SoGroup * group = (SoGroup *)node; // safe downward cast, knows the type
}
}For application programmers wanting to extend the library with new nodes, engines, nodekits, draggers or others: this method needs to be overridden in all subclasses. This is typically done as part of setting up the full type system for extension classes, which is usually accomplished by using the pre-defined macros available through for instance Inventor/nodes/SoSubNode.h (SO_NODE_INIT_CLASS and SO_NODE_CONSTRUCTOR for node classes), Inventor/engines/SoSubEngine.h (for engine classes) and so on. For more information on writing Coin extensions, see the class documentation of the toplevel superclasses for the various class groups. Implements SoBase.
const SoFieldData * SoShapeHints::getFieldData (void) const [protected], [virtual]Returns a pointer to the class-wide field data storage object for this instance. If no fields are present, returns NULL. Reimplemented from SoFieldContainer.
void SoShapeHints::doAction (SoAction * action) [virtual]This function performs the typical operation of a node for any action. Reimplemented from SoNode. References creaseAngle, faceType, SoAction::getState(), SoField::isDefault(), SoField::isIgnored(), SoNode::isOverride(), SoOverrideElement::setCreaseAngleOverride(), SoOverrideElement::setShapeHintsOverride(), shapeType, vertexOrdering, and SoNode::VRML1. Referenced by callback(), getBoundingBox(), GLRender(), and pick().
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. References doAction().
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. References doAction().
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. References doAction().
void SoShapeHints::pick (SoPickAction * action) [virtual]Action method for SoPickAction. Does common processing for SoPickAction action instances. Reimplemented from SoNode. References doAction().
Member Data Documentation
SoSFEnum SoShapeHints::vertexOrderingSpecifies 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. Referenced by doAction(), and SoShapeHints().
SoSFEnum SoShapeHints::shapeTypeHint about whether or not shapes are known to be 'closed'. Default value is SoShapeHints::UNKNOWN_SHAPE_TYPE. Referenced by doAction(), and SoShapeHints().
SoSFEnum SoShapeHints::faceTypeHint about whether or not polygon faces are known to be convex. Default value is SoShapeHints::CONVEX. Referenced by doAction(), and SoShapeHints().
SoSFFloat SoShapeHints::creaseAngleWhen 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. Referenced by doAction(), and SoShapeHints().
AuthorGenerated automatically by Doxygen for Coin from the source code. 0
Johanes Gumabo
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