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       SoShapeHints -

       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.


       #include <Inventor/nodes/SoShapeHints.h>

       Inherits SoNode.

   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 }
       enum WindingType { NO_WINDING_TYPE = 0 }

   Public Member Functions
       virtual SoType getTypeId (void) const
           Returns the type identification of an object derived from a class inheriting SoBase.
           This is used for run-time type checking and 'downward' casting.
       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 Functions
       static SoType getClassTypeId (void)
       static void initClass (void)

   Public Attributes
       SoSFEnum vertexOrdering
       SoSFEnum shapeType
       SoSFEnum faceType
       SoSFEnum windingType
       SoSFBool useVBO
       SoSFFloat creaseAngle

   Protected Member Functions
       virtual const SoFieldData * getFieldData (void) const
       virtual ~SoShapeHints ()

   Static Protected Member Functions
       static const SoFieldData ** getFieldDataPtr (void)

   Additional Inherited Members

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.

       Here is an example on how to display a scene in wireframe mode which only shows the
       triangles facing towards the camera.

       #include <Inventor/nodes/SoCone.h>
       #include <Inventor/nodes/SoDrawStyle.h>
       #include <Inventor/nodes/SoLightModel.h>
       #include <Inventor/nodes/SoSeparator.h>
       #include <Inventor/nodes/SoShapeHints.h>
       #include <Inventor/Win/SoWin.h>
       #include <Inventor/Win/viewers/SoWinExaminerViewer.h>

       int main(int, char * argv[])
         HWND window = SoWin::init(argv[0]);

         SoSeparator * root = new SoSeparator;

         // wireframe
         SoDrawStyle * drawStyle = new SoDrawStyle;
         drawStyle->style = SoDrawStyle::LINES;

         // back-face culling
         SoShapeHints * shapeHints = new SoShapeHints;
         shapeHints->vertexOrdering = SoShapeHints::COUNTERCLOCKWISE;
         shapeHints->shapeType = SoShapeHints::SOLID;

         // keep a solid color
         SoLightModel * lightModel = new SoLightModel;
         lightModel->model = SoLightModel::BASE_COLOR;

         // a cone
         SoCone * cone = new SoCone;

         // set up a window
         SoWinExaminerViewer * viewer = new SoWinExaminerViewer(window);
         SbViewportRegion vpRegion = viewer->getViewportRegion();

         delete viewer;
         return 0;

       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

       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.
       ShapeHints {
           vertexOrdering UNKNOWN_ORDERING
           shapeType UNKNOWN_SHAPE_TYPE
           faceType CONVEX
           creaseAngle 0

Member Enumeration Documentation

   enum SoShapeHints::VertexOrdering
       Enumeration of available ways to specify ordering of vertices for a polygon.
              Ordering not known, render both sides of the polygon.
              Vertices are specified in a clockwise order.
              Vertices are specified in a counter-clockwise order.
   enum SoShapeHints::ShapeType
       Enumeration of different shape types.
              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::FaceType
       Enumeration of polygon face types.
              Signifies: nothing is known about subsequent polygon data, be conservative when
       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
       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

Constructor & Destructor Documentation

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

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
       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.
   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.

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
   SoSFEnum SoShapeHints::faceType
       Hint about whether or not polygon faces are known to be convex. Default value is
   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
       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.
       The angle is specified in radians, and the default value is 0.0, meaning no smoothing will
       be done by default.


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