SoBufferObject Class Reference
[Devices]

Abstract base class for buffer object management More...

#include <Inventor/devices/SoBufferObject.h>

Inheritance diagram for SoBufferObject:

Public Types
enum	AccessMode { READ_ONLY, SET, READ_WRITE }
Public Member Functions
void	lockBuffer ()
void	unlockBuffer ()
virtual bool	setSize (size_t size)
virtual size_t	getSize () const
virtual void *	map (AccessMode accessMode, size_t offset=0, size_t count=SO_BUFFER_SIZE_ALL)
virtual void	unmap ()
virtual void	map (SoBufferObject *targetBufferObject, AccessMode accessMode, size_t startPosition=0, size_t mappingSize=SO_BUFFER_SIZE_ALL)
virtual void	unmap (SoBufferObject *bufferObject)
virtual void	memcpy (SoBufferObject *sourceBufferObject, size_t destOffset=0, size_t sourceOffset=0, size_t copySize=SO_BUFFER_SIZE_ALL)
virtual void	memset (void *value, size_t valueSize=1, size_t offset=0, size_t count=SO_BUFFER_SIZE_ALL)
virtual SoBufferObject *	createInstance () const =0
virtual void	clearInstance ()=0
SoDeviceContext *	getContext () const
SoBufferObject *	getMappedBufferObject ()
AccessMode	getMappedBufferObjectAccessMode ()
size_t	getMappedBufferObjectPosition () const
size_t	getMappedBufferObjectSize () const
Static Public Member Functions
static SoCpuBufferObjectCache *	getBufferObjectCache ()
Friends
class	SoCpuBufferObject

Detailed Description

Abstract base class for buffer object management

This class provides generic functions to manage buffer objects.

There are specific implementations of this class for buffer objects on each type of device:

SoCpuBufferObject: A buffer in CPU system memory.
SoGpuBufferObject: A buffer in GPU memory.
SoGLBufferObject: A buffer in GPU memory managed through the OpenGL API.

In many cases the abstract SoBufferObject methods allow the application to handle buffer objects without knowing the specific type of the buffer. This is very convenient when computation is implemented on multiple devices.

Since version 8.0, some Open Inventor classes take or return data using an SoBufferObject (or derived class). For example texture images (see SoSFImage), geometry data (see SoBufferedShape) and tiles of volume data (see SoLDMDataAccess).

Creating a buffer object

: Before creating a non-CPU buffer object you must bind (then unbind) a valid context for the target device. For example, to create a GPU buffer object (SoGpuBufferObject) you can bind the viewer's context using methods in the view class or you can use the class SoGLContext. See the example on the SoGpuBuffer page. For an existing buffer object you can use the buffer's bind()/unbind() methods or get a valid context to bind using the getContext() method. Binding this context is necessary before changing buffer properties or calling setSize(), memcpy(), memset(), etc.

SoBufferObject classes are reference counted objects (just like nodes, paths, etc). Therefore you cannot create an SoBufferObject on the stack. And to delete an SoBufferObject you must ref and unref the object. The SoRef smart pointer is a safe and convenient way to create buffer objects. For example, the following code will NOT compile:

    {
      SoCpuBufferObject cpuObj; // ILLEGAL
      . . .
    }
    // OR...
    {
      SoCpuBufferObject* cpuObj = new SoCpuBufferObject;
      cpuObj->map(SoBufferObject::READ_ONLY);
      . . .
      cpuObj->unmap();
      delete cpuObj;  // ILLEGAL
    }

Use the following code instead:

    {
      SoRef<SoCpuBufferObject> cpuObj = new SoCpuBufferObject;
      cpuObj->map(SoBufferObject::READ_ONLY);
      . . .
      cpuObj->unmap();
    }
    // OR...
    {
      SoCpuBufferObject* cpuObj = new SoCpuBufferObject;
      cpuObj->ref();
      cpuObj->map(SoBufferObject::READ_ONLY);
      . . .
      cpuObj->unmap();
      cpuObj->unref();
    }

Allocating memory in a buffer object:

: Use the setSize() method to allocate memory in a buffer object. (Note that you must bind a valid context before calling this method on non-CPU buffer objects.) Generally buffer objects have zero size when created. However some buffer object classes have a constructor that takes an existing block of memory as a parameter. In that case the initial size is non-zero. You must allocate memory before copying data into a buffer object using either the memcpy() method or a direct pointer . Memory is automatically allocated, if necessary, when a buffer object is mapped into another buffer object.

Loading data and retrieving data:

Some buffer objects, e.g. SoCpuBufferObject, have a constructor that takes an existing block of memory as a parameter. In this case the buffer object is automatically set to the necessary size to contain the specified data. Creating an SoCpuBufferObect that "wraps" the existing data is usually the first step in loading data into a non-CPU buffer using memcpy() or map().

The memcpy() methods copy data into a buffer object from another buffer object. For example to copy data into an OpenGL buffer from a CPU buffer. Before using these methods on a non-CPU buffer object, you must bind (then unbind) a valid context for the target device. The buffer object must be large enough (have enough memory allocated) to hold the data. See the allocating memory topic above.

The memset() methods fill a buffer object with a specified value. Before using these methods on a non-CPU buffer object, you must bind (then unbind) a valid context for the target device. The buffer object must be large enough (have enough memory allocated) to hold the data. See the allocating memory topic above.

The map() methods that have a buffer object parameter "map" one buffer object into another, usually to allow the data to be accessed on a different device. When the access mode is READ_ONLY or READ_WRITE, the contents of the source buffer are available through the target buffer object after the map() call. If necessary, Open Inventor will automatically do an inter-device transfer of the data. When the access mode is SET or READ_WRITE, the contents of the modified target buffer object are available through the source buffer object after the unmap() call. If necessary, Open Inventor will automatically do an inter-device data transfer.

Some buffer object classes provide a map() method that maps the buffer's data into CPU memory and returns a pointer. If necessary, Open Inventor will automatically do an inter-device transfer of the data. While the buffer is mapped the application can directly modify its data using the returned pointer. If the access mode is SET or READ_WRITE, the modified data will be available through the buffer object after the unmap() call. If necessary, Open Inventor will automatically do an inter-device data transfer.

Member Enumeration Documentation

enum SoBufferObject::AccessMode

This enum provides the possible access modes for a mapped buffer object.

Enumerator:

READ_ONLY	The target buffer initially has the same contents as the source buffer.
SET	The target buffer contents are initially undefined (although they may be the same as the source buffer) but the source buffer will contain the contents of the target buffer after the unmap.
READ_WRITE	The target buffer initially has the same contents as the source buffer and the source buffer will contain the contents of the target buffer after the unmap.

Member Function Documentation

virtual void SoBufferObject::clearInstance ( ) [pure virtual]

Free the memory allocated by the buffer object.

Implemented in SoCpuBufferObject, SoGLBufferObject, SoGpuBufferObject, and SoInteropBufferObject.

virtual SoBufferObject* SoBufferObject::createInstance ( ) const [pure virtual]

Create a new buffer with the same properties as the current one.

The new instance will have the same context or device properties, but no memory is allocated.

Implemented in SoCpuBufferObject, SoGLBufferObject, SoGpuBufferObject, SoInteropBufferObject, and SoCpuBufferBitSet.

static SoCpuBufferObjectCache* SoBufferObject::getBufferObjectCache ( ) [static]

Returns the cache manager object.

This object manages a cache of SoCpuBufferObject objects. SoBufferObject creates an instance of this class that is primarily used for the LDM tile cache (see SoLDMGlobalResourceParameters for more information). The buffer object cache can be accessed using the SoBufferObject static method getBufferObjectCache. Default size is 50 or the value of OIV_BUFFER_OBJECT_CACHE_SIZE.

SoDeviceContext* SoBufferObject::getContext ( ) const

Returns the device context where this buffer is valid.

Returns:: A device context.

SoBufferObject* SoBufferObject::getMappedBufferObject ( )

Returns a pointer to the buffer object which is mapped by the actual object.

AccessMode SoBufferObject::getMappedBufferObjectAccessMode ( )

Returns the access mode used for the buffer mapping.

size_t SoBufferObject::getMappedBufferObjectPosition ( ) const

Returns the position in the source buffer mapped in this buffer.

Returns:: Returns a position in bytes.

size_t SoBufferObject::getMappedBufferObjectSize ( ) const

Returns the size of the mapped area in bytes.

Returns:: The size of the mapped area.

virtual size_t SoBufferObject::getSize ( ) const [virtual]

Returns the size, in bytes, of the buffer object.

Returns:: The size in bytes of the buffer object.

void SoBufferObject::lockBuffer ( )

Locks the buffer against concurrent calls from different threads.

This is a blocking call. In other words it will not return immediately if another thread currently has the buffer locked.

virtual void SoBufferObject::map	(	SoBufferObject *	targetBufferObject,
		AccessMode	accessMode,
		size_t	startPosition = `0`,
		size_t	mappingSize = `SO_BUFFER_SIZE_ALL`
	)			`[virtual]`

Maps the current buffer object into the specified buffer object.

This is useful in order to use a buffer in multiple contexts. The default is to map the entire contents of this buffer, but it is also possible to map a subset of this buffer's memory using the startPosition and mappingSize parameters.

A source buffer may be mapped into multiple target buffers. However a target buffer can only be mapped from one source buffer at a time. If a different source buffer is currently mapped into the target buffer, it is automatically unmapped and may be left in an undefined state.

Note: If the current buffer is empty or startPosition is beyond the end of the managed memory, the buffer is not mapped (and an error message is issued in debug builds).

Parameters:

	targetBufferObject	The buffer object which will be the mapped version of this buffer.
	accessMode	The access mode used for the mapping.
	startPosition	Offset (in bytes) in source buffer to map from (default is start of buffer).
	mappingSize	Size (in bytes) from the startPosition, if SO_BUFFER_SIZE_ALL then the whole buffer is mapped.

virtual void* SoBufferObject::map	(	AccessMode	accessMode,
		size_t	offset = `0`,
		size_t	count = `SO_BUFFER_SIZE_ALL`
	)			`[virtual]`

Map the buffer to a system memory address and allows the mapping of a sub part of the buffer object into CPU memory.

Notes:

The unmap() method must be called before using the buffer.

Returns:: Pointer to data in the mapped region of the buffer memory.

Reimplemented in SoGLBufferObject, SoCpuBufferBitSet, SoCpuBufferCompressed, SoCpuBufferFromVolumeReader, and SoCpuBufferUniform.

virtual void SoBufferObject::memcpy	(	SoBufferObject *	sourceBufferObject,
		size_t	destOffset = `0`,
		size_t	sourceOffset = `0`,
		size_t	copySize = `SO_BUFFER_SIZE_ALL`
	)			`[virtual]`

Copies data from the specified buffer object into this buffer object.

If the size or the offset are not valid an error is reported (SoDebugError). This buffer is not resized, if it is too small an error is reported.

Warning:: Source and destination overlaping support is implementation dependent, if not supported an error is reported.

Parameters:

	sourceBufferObject	The buffer object to be copied.
	destOffset	The starting offset in the destination buffer object, useful for data subsets.
	sourceOffset	The starting offset in the source buffer object, useful for data subsets.
	copySize	The number of bytes to copy from the source buffer object (SO_BUFFER_SIZE_ALL means all).

virtual void SoBufferObject::memset	(	void *	value,
		size_t	valueSize = `1`,
		size_t	offset = `0`,
		size_t	count = `SO_BUFFER_SIZE_ALL`
	)			`[virtual]`

This function sets the contents of (or a portion of) this buffer object to the specified value.

The valueSize parameter provides a way to do a memset with float, short, byte, etc values. The number of bytes set in this buffer object is exactly valueSize*count. The first byte changed in this buffer is given by the offset argument.

Parameters:

	value	is a pointer to the value to set in the buffer.
	valueSize	The size in bytes of the value. Default is 1 byte.
	offset	The offset in bytes (where to start setting values). Default is 0.
	count	The number of values to set. Default is number of bytes in buffer.

EXAMPLE

   unsigned char memset_value = 0;
   buffer->memset( &memset_value );

Reimplemented in SoCpuBufferBitSet, and SoCpuBufferUniform.

virtual bool SoBufferObject::setSize ( size_t size ) [virtual]

Sets the size in bytes of the buffer object.

If the requested size is the same as the current size, this method does nothing and returns true. If there is existing memory that is owned by the buffer object, that memory is released. If the requested size is zero, the buffer object is now empty.

Parameters:

size

The requested size in bytes.

Returns:: true if the operation was successful.

Reimplemented in SoGLBufferObject, and SoGpuBufferObject.

void SoBufferObject::unlockBuffer ( )

Unlocks the buffer object.

If a thread calls lockBuffer() then it must call unlockBuffer() to allow other threads to lock the buffer.

virtual void SoBufferObject::unmap ( SoBufferObject * bufferObject ) [virtual]

Unmap this buffer from the specified buffer object.

In other words, remove the specified target buffer from the list of buffers which this buffer is mapped to. If the access mode supports writing, the specified buffer is sync'd with the current buffer. An error is reported (in debug builds) if the buffer is not mapped to the specified buffer

Parameters:

bufferObject

Buffer to be unmapped.

virtual void SoBufferObject::unmap ( ) [virtual]

Unmaps the buffer from CPU address space.

Reimplemented in SoGLBufferObject, SoCpuBufferBitSet, SoCpuBufferCompressed, SoCpuBufferFromVolumeReader, and SoCpuBufferUniform.

Friends And Related Function Documentation

friend class SoCpuBufferObject [friend]

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

Inventor/devices/SoBufferObject.h

SoBufferObject Class Reference [Devices]

Public Types

Public Member Functions

Static Public Member Functions

Friends

Detailed Description

SEE ALSO

Member Enumeration Documentation

Member Function Documentation

Friends And Related Function Documentation

SoBufferObject Class Reference
[Devices]