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SoShapeHints(3) | Coin | SoShapeHints(3) |
NAME¶
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.SYNOPSIS¶
#include <Inventor/nodes/SoShapeHints.h> Inherits SoNode.Public Types¶
enum VertexOrdering { UNKNOWN_ORDERING = SoShapeHintsElement::UNKNOWN_ORDERING, CLOCKWISE = SoShapeHintsElement::CLOCKWISE, COUNTERCLOCKWISE = SoShapeHintsElement::COUNTERCLOCKWISE }
Public Member Functions¶
virtual SoType getTypeId (void) const
Static Public Member Functions¶
static SoType getClassTypeId (void)
Public Attributes¶
SoSFEnum vertexOrdering
Protected Member Functions¶
virtual const SoFieldData * getFieldData (void) const
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; root->addChild(drawStyle); // back-face culling SoShapeHints * shapeHints = new SoShapeHints; shapeHints->vertexOrdering = SoShapeHints::COUNTERCLOCKWISE; shapeHints->shapeType = SoShapeHints::SOLID; root->addChild(shapeHints); // keep a solid color SoLightModel * lightModel = new SoLightModel; lightModel->model = SoLightModel::BASE_COLOR; root->addChild(lightModel); // a cone SoCone * cone = new SoCone; root->addChild(cone); // set up a window SoWinExaminerViewer * viewer = new SoWinExaminerViewer(window); SbViewportRegion vpRegion = viewer->getViewportRegion(); viewer->setSceneGraph(root); viewer->show(); SoWin::mainLoop(); 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 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:
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- vertexOrdering == CLOCKWISE or COUNTERCLOCKWISE, shapeType == SOLID: causes primitives to be backface culled and rendered with one-sided lighting.
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- vertexOrdering == CLOCKWISE or COUNTERCLOCKWISE, shapeType == UNKNOWN_SHAPE_TYPE: primitives are not backface culled, and they are rendered with two-sided lighting.
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- 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.
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. 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::ShapeType¶
Enumeration 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::FaceType¶
Enumeration of polygon face types. Enumerator- UNKNOWN_FACE_TYPE
- Signifies: nothing is known about subsequent polygon data, be conservative when rendering.
- CONVEX
- Subsequent faces are all convex, so turn off the check for and tessellation of inconvex faces.
Constructor & Destructor Documentation¶
SoShapeHints::SoShapeHints (void)¶
Constructor.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 } }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 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. The angle is specified in radians, and the default value is 0.0, meaning no smoothing will be done by default.Author¶
Generated automatically by Doxygen for Coin from the source code.Thu May 29 2014 | Version 4.0.0a |