Provided by: libcoin60-doc_3.1.3-2_all bug

NAME

       SoShadowGroup -

       The SoShadowGroup node is a group node used for shadow rendering.

       Children of this node can recieve shadows, and cast shadows on other children. Use the
       SoShadowStyle node to control shadow casters and shadow receivers.

SYNOPSIS

       #include <FXViz/nodes/SoShadowGroup.h>

       Inherits SoSeparator.

   Public Types
       enum VisibilityFlag { ABSOLUTE_RADIUS, LONGEST_BBOX_EDGE_FACTOR,
           PROJECTED_BBOX_DEPTH_FACTOR }

   Public Member Functions
       SoShadowGroup (void)
       virtual void GLRenderBelowPath (SoGLRenderAction *action)
       virtual void GLRenderInPath (SoGLRenderAction *action)
       virtual void notify (SoNotList *nl)
       void enableSubgraphSearchOnNotify (const SbBool onoff)

   Static Public Member Functions
       static void initClass (void)
       static void init (void)
       static SbBool isSupported (void)

   Public Attributes
       SoSFBool isActive
       SoSFFloat intensity
       SoSFFloat precision
       SoSFFloat quality
       SoSFFloat smoothBorder
       SoSFBool shadowCachingEnabled
       SoSFFloat visibilityNearRadius
       SoSFFloat visibilityRadius
       SoSFEnum visibilityFlag
       SoSFFloat epsilon
       SoSFFloat threshold

   Protected Member Functions
       virtual ~SoShadowGroup ()

Detailed Description

       The SoShadowGroup node is a group node used for shadow rendering.

       Children of this node can recieve shadows, and cast shadows on other children. Use the
       SoShadowStyle node to control shadow casters and shadow receivers.

       Please note that all shadow casters will be rendered twice. Once to create the shadow map,
       and once for normal rendering. If you're having performance issues, you should consider
       reducing the number of shadow casters.

       The algorithm used to render the shadows is Variance Shadow Maps
       (http://www.punkuser.net/vsm/). As an extra bonus, all geometry rendered with shadows can
       also be rendered with per fragment phong lighting.

       This node will search its subgraph and calculate shadows for all SoSpotLight nodes. The
       node will use one texture unit for each spot light, so for this node to work 100%, you
       need to have num-spotlights free texture units while rendering the subgraph.

       Currently, we only support scenes with maximum two texture units active while doing shadow
       rendering (unit 0 and unit 1). This is due to the fact that we emulate the OpenGL shading
       model in a shader program, and we're still working on creating a solution that updates the
       shader program during the scene graph traversal. Right now a shader program is created
       when entering the SoShadowGroup node, and this is used for the entire subgraph.

       FILE FORMAT/DEFAULTS:

           SoShadowGroup {
             isActive TRUE
             intensity 0.5
             precision 0.5
             quality 0.5
             shadowCachingEnabled TRUE
             visibilityRadius -1.0
             visibilityFlag LONGEST_BBOX_EDGE_FACTOR

             epsilon 0.00001
             threshold 0.1
             smoothBorder 0.0

           }

       Example scene graph:

         #Inventor V2.1 ascii

         # to get some lighting when headlight is turned off in the viewer
         DirectionalLight { direction 0 0 -1 intensity 0.2 }

         ShadowGroup {
           quality 1 # to get per pixel lighting

           ShadowStyle { style NO_SHADOWING }

           SpotLight {
             location -8 -8 8.0
             direction 1 1 -1
             cutOffAngle 0.35
             dropOffRate 0.7
           }

           ShadowStyle { style CASTS_SHADOW_AND_SHADOWED }

           Separator {
             Complexity { value 1.0 }
             Material { diffuseColor 1 1 0 specularColor 1 1 1 shininess 0.9 }
             Shuttle { translation0 -3 1 0 translation1 3 -5 0 speed 0.25 on TRUE }
             Translation { translation -5 0 2 }
             Sphere { radius 2.0 }
           }

           Separator {
             Material { diffuseColor 1 0 0 specularColor 1 1 1 shininess 0.9 }
             Shuttle { translation0 0 -5 0 translation1 0 5 0 speed 0.15 on TRUE }
             Translation { translation 0 0 -3 }
             Cube { depth 1.8 }
           }
           Separator {
             Material { diffuseColor 0 1 0 specularColor 1 1 1 shininess 0.9 }
             Shuttle { translation0 -5 0 0 translation1 5 0 0 speed 0.3 on TRUE }
             Translation { translation 0 0 -3 }
             Cube { }
           }

           ShadowStyle { style SHADOWED }
           Coordinate3 { point [ -10 -10 -3, 10 -10 -3, 10 10 -3, -10 10 -3 ] }
           Material { specularColor 1 1 1 shininess 0.9 }

           Complexity { textureQuality 0.1 }
           Texture2 { image 2 2 3 0xffffff 0x225588 0x225588 0xffffff }
           Texture2Transform { scaleFactor 4 4 }
           FaceSet { numVertices 4 }
         }

       Since:
           Coin 2.5

Constructor & Destructor Documentation

   SoShadowGroup::SoShadowGroup (void) Default constructor.
   SoShadowGroup::~SoShadowGroup () [protected, virtual] Destructor.

Member Function Documentation

   void SoShadowGroup::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 SoSeparator.

   SbBool SoShadowGroup::isSupported (void) [static] Reports whether or not the shadow nodes can
       be used successfully on the current system.
       The result will depend on the specific qualities of the graphics card and OpenGL driver on
       the system.

       An important note about this function:

       The API design of this function has a serious shortcoming, as features of OpenGL should be
       tested within an OpenGL context, and this function does not provide any means of
       specifying the context. It is implemented in this manner to match the function signature
       in TGS Inventor, for compatibility reasons.

       (A temporary offscreen OpenGL context is set up for the feature tests. This should usually
       be sufficient to decide whether or not the graphics driver / card supports the features
       needed for rendering shadows.)

       Since:
           Coin 3.1

   void SoShadowGroup::GLRenderBelowPath (SoGLRenderAction *action) [virtual] SGI Open Inventor
       v2.1 obsoleted support for SoGLRenderAction::addMethod(). Instead, GLRender() might be
       called directly, and to optimize traversal, the SoSeparator node calls GLRenderBelowPath
       whenever the path code is BELOW_PATH or NO_PATH (path code is guaranteed not to change).
       To be compatible with SGI's Inventor (and thereby also TGS') we have chosen to follow
       their implementation in this respect.
       SoSeparator::GLRenderBelowPath() do not traverse its children using
       SoChildList::traverse(), but calls GLRenderBelowPath() directly for all its children.

       Reimplemented from SoSeparator.

   void SoShadowGroup::GLRenderInPath (SoGLRenderAction *action) [virtual] Implements the
       SoAction::IN_PATH traversal method for the rendering action.
       Reimplemented from SoSeparator.

   void SoShadowGroup::notify (SoNotList *l) [virtual] Notifies all auditors for this instance
       when changes are made.
       Reimplemented from SoSeparator.

   void SoShadowGroup::enableSubgraphSearchOnNotify (const SbBoolonoff) By default, the
       SoShadowGroup node will search its subgraph for new spot lights whenever a group node
       under it is touched. However, this might lead to bad performance in some cases so it's
       possible to disable this feature using this method. If you do disable this feature, make
       sure you enable it again before inserting a new spot light, or insert all spot lights in
       the scene graph before you render the scene once, and just set 'on' to FALSE if you want
       to toggle spot lights on/off on the fly.
       Since:
           Coin 2.6

Member Data Documentation

   SoSFBool SoShadowGroup::isActive Use this field to turn shadow rendering for the subgraph
       on/off. Default value is TRUE.
   SoSFFloat SoShadowGroup::intensity Not used yet. Provided for TGS Inventor compatibility.
   SoSFFloat SoShadowGroup::precision Use to calculate the size of the shadow map. A precision of
       1.0 means the maximum shadow buffer size will be used (typically 2048x2048 on current
       graphics cards). Default value is 0.5.
   SoSFFloat SoShadowGroup::quality Can be used to tune the shader program complexity. A higher
       value will mean that more calculations are done per-fragment instead of per-vertex.
       Default value is 0.5.
   SoSFInt32 SoShadowGroup::smoothBorder SoShadowGroup::VisibilityFlag
       SoShadowGroup::ABSOLUTE_RADIUS
       The absolute values of visibilityNearRadius and visibilityRadius will be used.

       SoShadowGroup::VisibilityFlag SoShadowGroup::LONGEST_BBOX_EDGE_FACTOR

       The longest bbox edge will be used to determine near and far clipping planes.

       SoShadowGroup::VisibilityFlag SoShadowGroup::PROJECTED_BBOX_DEPTH_FACTOR

       The bbox depth (projected to face the camera) will be used to calculate the clipping
       planes.

       We have some problems with this feature so it's not supported at the moment.

       Used to add shadow border smoothing. This is currently done as a post processing step on
       the shadow map. The algorithm used is Gauss Smoothing, but in the future we'll probably
       change this, and use a summed area sampling merhod instead. The value should be a number
       between 0 (no smoothing), and 1 (max smoothing).

       If you want to enable smoothing, choosing a low value (~0.1) works best in the current
       implementation.

       Default value is 0.0.

   SoSFBool SoShadowGroup::shadowCachingEnabled Not used yet. Provided for TGS Inventor
       compatibility.
   SoSFFloat SoShadowGroup::visibilityNearRadius Can be used to manually set the near clipping
       plane of the shadow maps. If a negative value is provided, the group will calculate a near
       plane based on the bounding box of the children. Default value is -1.0.
       See also:
           visibilityFlag

   SoSFFloat SoShadowGroup::visibilityRadius Can be used to manually set the far clipping plane
       of the shadow maps. If a negative value is provided, the group will calculate a near plane
       based on the bounding box of the children. Default value is -1.0.
       See also:
           visibilityFlag

   SoSFEnum SoShadowGroup::visibilityFlag Determines how visibilityRadius and visibilitNearRadius
       is used to calculate near and far clipping planes for the shadow volume.
   SoSFFloat SoShadowGroup::epsilon Epsilon is used to offset the shadow map depth from the model
       depth. Should be set to as low a number as possible without causing flickering in the
       shadows or on non-shadowed objects. Default value is 0.00001.
   SoSFFloat SoShadowGroup::threshold Can be used to avoid light bleeding in merged shadows cast
       from different objects.
       A threshold to completely eliminate all light bleeding can be computed from the ratio of
       overlapping occluder distances from the light's perspective. See
       http://forum.beyond3d.com/showthread.php?t=38165 for a discussion about this problem.

Author

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