# SoGLRenderAction Class Reference
[Actions]

`#include <Inventor/actions/SoGLRenderAction.h>`

Inheritance diagram for SoGLRenderAction:

List of all members.

## Detailed Description

The SoGLRenderAction class renders the scene graph with OpenGL calls.

Applying this method at a root node for a scene graph, path or pathlist will render all geometry contained within that instance to the current OpenGL context.

## Public Types

typedef AbortCode | SoGLRenderAbortCB (void *userdata)
enum | TransparencyType { SCREEN_DOOR, ADD, DELAYED_ADD, SORTED_OBJECT_ADD, BLEND, DELAYED_BLEND, SORTED_OBJECT_BLEND, SORTED_OBJECT_SORTED_TRIANGLE_ADD, SORTED_OBJECT_SORTED_TRIANGLE_BLEND, NONE }
enum | AbortCode { CONTINUE, ABORT, PRUNE, DELAY }

## Public Member Functions

| SoGLRenderAction (const SbViewportRegion &viewportregion)
virtual | ~SoGLRenderAction ()
void | setViewportRegion (const SbViewportRegion &newregion)
const SbViewportRegion & | getViewportRegion (void) const
void | setUpdateArea (const SbVec2f &origin, const SbVec2f &size)
void | getUpdateArea (SbVec2f &origin, SbVec2f &size) const
void | setAbortCallback (SoGLRenderAbortCB *const func, void *const userdata)
void | setTransparencyType (const TransparencyType type)
TransparencyType | getTransparencyType (void) const
void | setSmoothing (const SbBool smooth)
SbBool | isSmoothing (void) const
void | setNumPasses (const int num)
int | getNumPasses (void) const
void | setPassUpdate (const SbBool flag)
SbBool | isPassUpdate (void) const
void | setPassCallback (SoGLRenderPassCB *const func, void *const userdata)
void | setCacheContext (const uint32_t context)
uint32_t | getCacheContext (void) const
void | addDelayedPath (SoPath *path)
SbBool | isRenderingDelayedPaths (void) const
SbBool | handleTransparency (SbBool istransparent=FALSE)
int | getCurPass (void) const
SbBool | abortNow (void)
void | setRenderingIsRemote (SbBool isremote)
SbBool | getRenderingIsRemote (void) const
virtual void | invalidateState (void)
void | addPreRenderCallback (SoGLPreRenderCB *func, void *userdata)
void | removePreRenderCallback (SoGLPreRenderCB *func, void *userdata)

## Static Public Member Functions

void | initClass (void)

## Protected Member Functions

virtual void | beginTraversal (SoNode *node)
virtual void | endTraversal (SoNode *node)

## Friends

class | SoGLRenderActionP

## Member Typedef Documentation

typedef SoGLRenderAction::SoGLRenderAbortCB

Abort callbacks should be of this type.

See also:
  setAbortCallback()

## Member Enumeration Documentation

enum SoGLRenderAction::TransparencyType

Various settings for how to do rendering of transparent objects in the scene. Some of the settings will provide faster rendering, while others gives you better quality rendering.

Note that doing correct rendering of multiple transparent objects often fails, because to be 100% correct, all polygons needs to be rendered in sorted order, and polygons can't intersect each other. In a dynamic scene graph it is often impossible to guarantee that no polygons intersect, and finding an algorithm that does correct sorting of polygons for all possible cases is very hard and time-consuming.

The highest quality transparency mode in the original SGI / TGS Open Inventor is SoGLRenderAction::SORTED_OBJECT_BLEND, where all transparent objects are rendered in sorted order in a rendering pass after all opaque objects. However, this mode does not sort the polygons, and if you have an object where some polygon A is behind some other polygon B, the transparency will only be correct if A happens to be rendered before B. For other camera angles, where B is behind A, the transparency will not be correct.

In Coin we have a new transparency mode that solves some of these problems: SoGLRenderAction::SORTED_OBJECT_SORTED_TRIANGLE_BLEND. In addition to sorting the objects, all polygons inside each object is also sorted back-to-front when rendering. But, if you have intersecting objects and/or intersecting polygons, even this transparency mode will fail. Also, because of the polygon sorting, this transparency mode is quite slow. It is possible to speed things up using the SoTransparencyType node, though, which enables you to set different transparency modes for different parts of the scene graph. If you have only have a few objects where you need to sort the polygons, you can use SoGLRenderAction::SORTED_OBJECT_SORTED_TRIANGLE_BLEND for those, and for instance SoGLRenderAction::SORTED_OBJECT_BLEND for all other transparent objects.

See also:
  SoTransparencyType

Enumeration values:

  SCREEN_DOOR

  Transparent triangles are rendered with a dither pattern. This is a fast (on most GFX cards) but not-so-high-quality transparency mode.

  One particular feature of this mode is that you are guaranteed that it always renders the transparent parts of the scene correct with regard to internal depth ordering of objects / polygons, something which is not the case for any other transparency mode.

  ADD | Transparent objects are rendered using additive alpha blending. Additive blending is probably mostly used to create special transparency effects. The new pixel color is calculated as the current pixel color plus the source pixel color multiplied with the source pixel alpha value.
  DELAYED_ADD | SoGLRenderAction::DELAYED_ADD Transparent objects are rendered using additive alpha blending, in a second rendering pass with depth buffer updates disabled.
  SORTED_OBJECT_ADD | Transparent objects are rendered using additive alpha blending. Opaque objects are rendered first, and transparent objects are rendered back to front with z-buffer updates disabled.

  BLEND

  Transparent objects are rendered using multiplicative alpha blending.

  Multiplicative alpha blending is the blending type that is most often used to render transparent objects. The new pixel value is calculated as the old pixel color multiplied with one minus the source alpha value, plus the source pixel color multiplied with the source alpha value.

  We recommend that you use this transparency mode if you have only one transparent object in your scene, and you know that it will be rendered after the opaque objects.

  DELAYED_BLEND

  Transparent objects are rendered using multiplicative alpha blending, in a second rendering pass with depth buffer updates disabled.

  Use this transparency type when you have one transparent object, or several transparent object that you know will never overlap (when projected to screen). Since the transparent objects are rendered after opaque ones, you'll not have to worry about putting the transparent objects at the end of your scene graph. It will not be as fast as the BLEND transparency type, of course, since the scene graph is traversed twice.

  SORTED_OBJECT_BLEND

  Transparent objects are rendered using multiplicative alpha blending, Opaque objects are rendered first, and transparent objects are rendered back to front with z-buffer updates disabled.

  Use this transparency mode when you have several transparent object that you know might overlap (when projected to screen). This method will require 1 + num_transparent_objects rendering passes. Path traversal is used when rendering transparent objects, of course, but it might still be slow if you have lots of state changes before your transparent object. When using this mode, we recommend placing the transparent objects as early as possible in the scene graph to minimize traversal overhead.

  SORTED_OBJECT_SORTED_TRIANGLE_ADD | This transparency type is a Coin extension versus the original SGI Open Inventor API. Transparent objects are rendered back to front, and triangles in each object are sorted back to front before rendering. See description for SORTED_OBJECT_SORTED_TRIANGLE_BLEND for more information about this transparency type.

  SORTED_OBJECT_SORTED_TRIANGLE_BLEND

  This transparency type is a Coin extension versus the original SGI Open Inventor API.

  Transparent objects are rendered back to front, and triangles in each object are sorted back to front before rendering.

  Use this transparency type when you have one (or more) transparent object(s) where you know triangles might overlap inside the object. This transparency type might be very slow if you have an object with lots of triangles, since all triangles have to be sorted before rendering, and an unoptimized rendering loop is used when rendering. Lines and points are not sorted before rendering. They are rendered as in the normal SORTED_OBJECT_BLEND transparency type.

  Please note that this transparency mode does not guarantee "correct" transparency rendering. It is almost impossible to find an algorithm that will sort triangles correctly in all cases, and intersecting triangles are not handled. Also, since each object is handled separately, two intersecting object will lead to incorrect transparency.

  NONE | This transparency type is a Coin extension versus the Open Inventor API. Turns off transparency for objects, even if transparency is set using an SoMaterial node.

enum SoGLRenderAction::AbortCode

The return codes which an SoGLRenderAbortCB callback function should use.

See also:
  setAbortCallback()

Enumeration values:

  CONTINUE | Continue rendering as usual.
  ABORT | Abort the rendering action immediately.
  PRUNE | Do not render the current node or any of its children, but continue the rendering traversal.
  DELAY | Delay rendering of the current node (and its children) until the next rendering pass.

## Constructor & Destructor Documentation

SoGLRenderAction::SoGLRenderAction | ( | const SbViewportRegion & | viewportregion | ) |

| Constructor. Sets up the render action for rendering within the given viewportregion.

SoGLRenderAction::~SoGLRenderAction | ( |  | ) | `[virtual]`

| Destructor, frees up all internal resources for action instance.

## Member Function Documentation

void SoGLRenderAction::initClass | ( | void |  | ) | `[static]`

| Initializes the run-time type system for this class, and sets up the enabled elements and action method list. Reimplemented from SoAction. Reimplemented in SoBoxHighlightRenderAction, and SoLineHighlightRenderAction.

void SoGLRenderAction::setViewportRegion | ( | const SbViewportRegion & | newregion | ) |

| Sets the viewport region for rendering. This will then override the region passed in with the constructor.

const SbViewportRegion & SoGLRenderAction::getViewportRegion | ( | void |  | ) | const

| Returns the viewport region for the rendering action.

void SoGLRenderAction::setUpdateArea | ( | const SbVec2f & | origin,
|  | const SbVec2f & | size
| ) |

| Sets the area of the OpenGL context canvas we should render into. The coordinates for origin and size should be normalized to be within [0.0, 1.0]. The default settings are <0.0, 0.0> for the origin and <1.0, 1.0> for the size, using the full size of the rendering canvas.

void SoGLRenderAction::getUpdateArea | ( | SbVec2f & | origin,
|  | SbVec2f & | size
| ) | const

| Returns information about the area of the rendering context window to be updated.

void SoGLRenderAction::setAbortCallback | ( | SoGLRenderAbortCB *const | func,
|  | void *const | userdata
| ) |

Sets the abort callback. The abort callback is called by the action for each node during traversal to check for abort conditions.

The callback method should return one of the SoGLRenderAction::AbortCode enum values to indicate how the action should proceed further.

Since the client SoGLRenderAbortCB callback function only has a single void* argument for the userdata, one has to do some additional work to find out which node the callback was made for. One can do this by for instance passing along the action pointer as userdata, and then call the SoGLRenderAction::getCurPath() method. The tail of the path will then be the last traversed node. Like this:

      // set up so we can abort or otherwise intervene with the render
      // traversal:
      myRenderAction->setAbortCallback(MyRenderCallback, myRenderAction);

      // [...]

      SoGLRenderAction::AbortCode
      MyRenderCallback(void * userdata)
      {
        SoGLRenderAction * action = (SoGLRenderAction *)userdata;
        SoNode * lastnode = action->getCurPath()->getTail();

        // [...]
        return SoGLRenderAction::CONTINUE;
      }

See also:
  SoGLRenderAction::AbortCode

void SoGLRenderAction::setTransparencyType | ( | const TransparencyType | type | ) |

Sets the transparency rendering method for transparent objects in the scene graph.

See also:
  SoGLRenderAction::TransparencyType

SoGLRenderAction::TransparencyType SoGLRenderAction::getTransparencyType | ( | void |  | ) | const

| Returns the transparency rendering type.

void SoGLRenderAction::setSmoothing | ( | const SbBool | smooth | ) |

| Sets (or unsets) smoothing. If the smoothing flag is `on`, Coin will try to use built-in features from the OpenGL implementation to smooth the appearance of otherwise jagged borders. This is a simple (and computationally non-intensive) way of doing anti-aliasing. Default value for this flag is to be `off`.

SbBool SoGLRenderAction::isSmoothing | ( | void |  | ) | const

| Returns whether smoothing is set or not.

void SoGLRenderAction::setNumPasses | ( | const int | num | ) |

| Sets the number of rendering passes. Default is 1, anything greater will enable antialiasing.

int SoGLRenderAction::getNumPasses | ( | void |  | ) | const

| Returns the number of rendering passes done on updates.

void SoGLRenderAction::setPassUpdate | ( | const SbBool | flag | ) |

| Sets whether each pass should render to screen or not.

SbBool SoGLRenderAction::isPassUpdate | ( | void |  | ) | const

Returns the value of the "show intermediate updates" flag.

See also:
  setPassUpdate()

void SoGLRenderAction::setPassCallback | ( | SoGLRenderPassCB *const | func,
|  | void *const | userdata
| ) |

| Sets the pass callback. The callback is called between each rendering pass.

void SoGLRenderAction::setCacheContext | ( | const uint32_t | context | ) |

Sets the OpenGL cache context key, which is used for deciding when to share OpenGL display lists.

Each SoGLRenderAction has a cache context id. This can be set using SoGLRenderAction::setCacheContext(). The cache context id must be unique, so that different texture objects and display lists are created for uncompatible GL contexts. For instance, when SoGLRenderAction traverses an SoTexture2 node, the node checks if it has a texture object created for the cache context. If not, a new texture object will be created and used when rendering.

See also:
  SoGLCacheContextElement::getUniqueCacheContext()

uint32_t SoGLRenderAction::getCacheContext | ( | void |  | ) | const

| Returns the cache context key for this rendering action instance.

void SoGLRenderAction::addDelayedPath | ( | SoPath * | path | ) |

| Adds a path to the list of paths to render after the current pass.

SbBool SoGLRenderAction::isRenderingDelayedPaths | ( | void |  | ) | const

| Returns a flag indicating whether or not we are currently rendering from the list of delayed paths of the scene graph.

SbBool SoGLRenderAction::handleTransparency | ( | SbBool | istransparent = FALSE | ) |

| Used by shape nodes or others which need to know whether or not they should immediately render themselves or if they should wait until the next pass.

int SoGLRenderAction::getCurPass | ( | void |  | ) | const

| Returns the number of the current rendering pass.

SbBool SoGLRenderAction::abortNow | ( | void |  | ) |

Returns `TRUE` if the render action should abort now based on user callback.

See also:
  setAbortCallback()

void SoGLRenderAction::setRenderingIsRemote | ( | SbBool | isremote | ) |

Let SoGLRenderAction instance know if application is running on the local machine or if the rendering instructions are sent over the network.

The flag is used to optimize rendering. For instance should the displaylist caching strategy be influenced by this flag to be more aggressive with the caching when rendering instructions are passed over the network.

Default value is `FALSE`. The value of the flag will not be changed internally from the Coin library code, as it is meant to be controlled from client code -- typically from the SoQt / SoXt / SoWin / SoGtk libraries.

See also:
  getRenderingIsRemote()

SbBool SoGLRenderAction::getRenderingIsRemote | ( | void |  | ) | const

Returns whether or not the application is running remotely.

See also:
  setRenderingIsRemote()

void SoGLRenderAction::invalidateState | ( | void |  | ) | `[virtual]`

| Invalidates the state, forcing it to be recreated at the next apply() invocation. Reimplemented from SoAction.

void SoGLRenderAction::addPreRenderCallback | ( | SoGLPreRenderCB * | func,
|  | void * | userdata
| ) |

Adds a callback which is invoked right before the scene graph traversal starts. All necessary GL initialization is then done (e.g. the viewport is correctly set), and this callback can be useful to, for instance, clear the viewport before rendering, or draw a bitmap in the background before rendering etc.

The callback is only invoked once (before the first rendering pass) when multi pass rendering is enabled.

Please note that SoSceneManager usually adds a callback to clear the GL buffers in SoSceneManager::render(). So, if you plan to for instance draw an image in the color buffer using this callback, you should make sure that the scene manager doesn't clear the buffer. This can be done either by calling SoSceneManager::render() with both arguments FALSE, or, if you're using one of our GUI toolkits (SoXt/SoQt/SoGtk/SoWin), call setClearBeforeRender() on the viewer.

This method is an extension versus the Open Inventor API.

See also:
  removePreRenderCallback().

void SoGLRenderAction::removePreRenderCallback | ( | SoGLPreRenderCB * | func,
|  | void * | userdata
| ) |

Removed a callback added with the addPreRenderCallback() method.

This method is an extension versus the Open Inventor API.

See also:
  addPreRenderCallback()

void SoGLRenderAction::beginTraversal | ( | SoNode * | node | ) | `[protected, virtual]`

This virtual method is called from SoAction::apply(), and is the entry point for the actual scenegraph traversal.

It can be overridden to initialize the action at traversal start, for specific initializations in the action subclasses inheriting SoAction.

Default method just calls traverse(), which any overridden implementation of the method must do too (or call SoAction::beginTraversal()) to trigger the scenegraph traversal.

Reimplemented from SoAction.

void SoGLRenderAction::endTraversal | ( | SoNode * | node | ) | `[protected, virtual]`

| This virtual method can be overridden to execute code after the scene graph traversal. Default method does nothing. Reimplemented from SoAction.

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

- SoGLRenderAction.h
- SoGLRenderAction.cpp