MIndexBuffer Class Reference


Detailed Description

Index buffer for use with MGeometry.

This class represents an index buffer with a specific data type.

When retrieving an index buffer for binding to custom shaders (MPxShaderOverride), resourceHandle() may be called to get the device dependent handle to the index buffer on the GPU.

When creating an index buffer to supply geometric data to Maya (MPxGeometryOverride), acquire() may be called to get a pointer to a block of memory to fill with said data. Once filled, commit() must be called to apply the data to the buffer.

Examples:

cgfxShaderNode.cpp, hwColorPerVertexShader.cpp, and hwPhongShader.cpp.

#include <MHWGeometry.h>

List of all members.

Public Member Functions

 MIndexBuffer (MGeometry::DataType type)
 Constructor.
 ~MIndexBuffer ()
 Destructor.
MGeometry::DataType dataType () const
 Get the data type of the buffer.
unsigned int size () const
 Get the size of the buffer in units of dataType().
void * resourceHandle () const
 Gets a graphics device dependent handle to the vertex indexing data.
void resourceHandle (void *handle, unsigned int size)
 Directly set the graphics-device-dependent hardware buffer resource handle.
bool hasCustomResourceHandle () const
 Returns true if this index buffer is using a custom resource handle set by the plugin using MIndexBuffer::resourceHandle(void*, unsigned int).
void * acquire (unsigned int size, bool writeOnly)
 Get a pointer to memory for the buffer.
void commit (void *buffer)
 Commit the data stored in the memory given by acquire() to the buffer.
void * map ()
 Get a read-only pointer to the existing content of the buffer.
void unmap ()
 Release the data exposed by map().
void * acquire (unsigned int size)
 This method is obsolete.

Static Public Member Functions

static const char * className ()
 Returns the name of this class.

Friends

class MGeometry

Constructor & Destructor Documentation

Constructor.

Parameters:
[in]typeThe data type for the index buffer

Destructor.

Note that it is an error to delete MIndexBuffer objects that are owned by or in use by an MGeometry object. Such actions may cause instability.


Member Function Documentation

MGeometry::DataType dataType ( ) const

Get the data type of the buffer.

Returns:
The data type of the buffer
Examples:
cgfxShaderNode.cpp, hwColorPerVertexShader.cpp, and hwPhongShader.cpp.
unsigned int size ( ) const

Get the size of the buffer in units of dataType().

Returns 0 if unallocated.

Returns:
Size of the buffer
Examples:
cgfxShaderNode.cpp, hwColorPerVertexShader.cpp, and hwPhongShader.cpp.
void * resourceHandle ( ) const

Gets a graphics device dependent handle to the vertex indexing data.

For OpenGL the return value is a pointer to an OpenGL identifier (GLuint) for a vertex buffer containing the indexing data. (e.g. using glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, handle)).

The index buffer identifier can be used to perform drawing of vertex buffer data identified by handles returned from MVertexBuffer::hwBuffer().

An example setup could be:

  1. For each vertex buffer query the handle.
  2. For each data handle set it up using the vertex buffer information (mapped to the draw API).
  3. Query the index handle.
  4. Use the index handle and index buffer information (mapped to the draw API) to perform drawing.

A NULL pointer will be returned if the graphics device dependent handle is not yet available.

If the pointer is not NULL, the value is only guaranteed to exist during the current draw. The value should never be cached or modified.

Returns:
A pointer to device dependent indexing data.
Examples:
cgfxShaderNode.cpp, hwColorPerVertexShader.cpp, and hwPhongShader.cpp.
void resourceHandle ( void *  handle,
unsigned int  size 
)

Directly set the graphics-device-dependent hardware buffer resource handle.

This will result in the creation of a custom user index buffer. Maya can render it, but the plugin owns the underlying device resource. When the Maya buffer is deleted, the actual hardware buffer will not be deleted. These buffers cannot be filled with Acquire or read-back with Map. They must be created and pre-filled, by the plugin.

Not currently supported in DirectX.

Parameters:
[in]handleFor OpenGL, handle is a pointer to a GLuint resource identifier for a vertex buffer object. This pointer must remain valid after MPxGeometryOverride::populateGeometry() returns, though not indefinitely after that.
[in]sizeThe number of indices in the indicated buffer.
bool hasCustomResourceHandle ( ) const

Returns true if this index buffer is using a custom resource handle set by the plugin using MIndexBuffer::resourceHandle(void*, unsigned int).

Returns:
True if this index buffer is using a custom resource handle.
void * acquire ( unsigned int  size,
bool  writeOnly 
)

Get a pointer to memory for the buffer.

This method is meant to be used in MPxGeometryOverride::populateGeometry() in order to provide data to Maya for drawing the associated object. The size of the buffer returned will be (size * sizeof(dataType())) bytes. The memory for the buffer is managed internally.

Note that not all data types are currently supported for index buffers. If the data type for this buffer is not supported this method will return NULL.

Parameters:
[in]sizeThe size of the buffer to acquire
[in]writeOnlySpecified if the returned memory should be uninitialized or filled with actual buffer content. When the current buffer content is not needed, it is preferable to set the writeOnly flag to true for better performance.
Returns:
A pointer to memory for the buffer, or NULL on failure
void commit ( void *  buffer)

Commit the data stored in the memory given by acquire() to the buffer.

If this method is not called, the acquired buffer will not be used in drawing. The pointer must be the same pointer returned from acquire().

Parameters:
[in]bufferA pointer to the data.
void * map ( )

Get a read-only pointer to the existing content of the buffer.

Writing new content in this memory block is not supported and can lead to unexpected behavior.

Returns:
A pointer to memory for the buffer, or NULL on failure
void unmap ( )

Release the data exposed by map().

If this method is not called, the buffer will not be recycled.

const char * className ( ) [static]

Returns the name of this class.

Returns:
The name of this class.
void * acquire ( unsigned int  size)

This method is obsolete.

Deprecated:
Please use acquire(unsigned int size, bool writeOnly) instead.

Get a pointer to memory for the buffer. This method is meant to be used in MPxGeometryOverride::populateGeometry() in order to provide data to Maya for drawing the associated object. The size of the buffer returned will be (size * sizeof(dataType())) bytes. The memory for the buffer is managed internally.

Note that not all data types are currently supported for index buffers. If the data type for this buffer is not supported this method will return NULL.

Parameters:
[in]sizeThe size of the buffer to acquire
Returns:
A pointer to memory for the buffer, or NULL on failure

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