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# MVaryingParameter Class Reference
OpenMayaRender - API module for rendering

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## Detailed Description

Geometric data cache.

The MVaryingParameter class provides a high-level interface to hardware shader varying parameters. By defining your shader's varying data through this class, you allow Maya to handle the attributes, editing, serialisation, requirements setup, and cache management for you in a standard way that ensure you'll be able to leverage future performance and functionlity improvements.

At setup time (either initial load or when the effect/technique is changed), your shader simply creates the list of parameters it requires, specifying the name, type, semantic of the parameters. At render time, you can then use the parameters to directly access the appropriate buffers for that surface data.

If you include a custom Attribute Editor template for your shader node, you can include these surface parameters by calling the AEhwShaderTemplateParameters script function. The following sample code provides a basic template you can modify - however your AE template can use as much or as little of this as you like:

    global int $yourShaderNameTemplateInitialised = 0;

    global proc AEyourShaderNameTemplate ( string $node )
    {
        global int $yourShaderNameTemplateInitialised;
        if( $yourShaderNameTemplateInitialised == 0)
        {
            source "AEhwShaderTemplate.mel";
            $yourShaderNameTemplateInitialised = 1;
        }

        AEhwShaderTemplateHeader( $node);

        // Insert custom attributes between the swatch and the parameters here

        AEhwShaderTemplateParameters( $node);

        // Insert custom attributes after the parameters here

        AEhwShaderTemplateFooter( $node);
    }

Examples:

  hlslShader.cpp, and hlslShader.h.

`#include <MVaryingParameter.h>`

List of all members.

## Public Types
enum | MVaryingParameterType { kInvalidParameter = -1, kStructure = 0, kFloat }
| Parameter types. More...
enum | MVaryingParameterSemantic { kNoSemantic = 0, kPosition, kNormal, kTexCoord, kColor, kWeight, kTangent = kWeight + 2, kBinormal }
| Parameter semantics (i.e. what the parameter represents). More...
## Public Member Functions
| MVaryingParameter ()
| Create an uninitialised (i.e.
| MVaryingParameter (const MString &name, MVaryingParameterType type, int minDimension=1, int maxDimension=1, MVaryingParameterSemantic semantic=kNoSemantic, bool invertTexCoords=false, const MString &semanticName="")
| Create a new varying parameter.
| MVaryingParameter (const MString &name, MVaryingParameterType type, int minDimension, int maxDimension, int dimension, MVaryingParameterSemantic semantic=kNoSemantic, const MString &destinationSet="", bool invertTexCoords=false, const MString &semanticName="")
| Create a new varying parameter.
| ~MVaryingParameter ()
| Class destructor.
const MVaryingParameter & | operator= (const MVaryingParameter &other)
| Assignment operator.
const MString | name () const
| Get the name of this parameter.
MVaryingParameter::MVaryingParameterType | type () const
| Get the type of this parameter.
MVaryingParameter::MVaryingParameterSemantic | semantic () const
| Get the semantic of this parameter.
const MString | semanticName () const
| Get the semantic name assigned to this parameter The semanticName is used to identify a custom vertex stream request in order to fill the stream with the appropriate data requested by a shader override.
MString | destinationSet () const
| Get the destination Set of this parameter.
int | dimension () const
| Get the dimension of this parameter.
MStatus | getBuffer (MGeometry &geometry, const void *&data, unsigned int &elements, unsigned int &count) const
| Get the data for this parameter as a system memory buffer.
MVaryingParameter::MVaryingParameterSemantic | getSourceType () const
| Get the type of data (e.g.
MString | getSourceSetName () const
| If the current data type supports data sets (e.g.
MStatus | setSource (MVaryingParameter::MVaryingParameterSemantic type, const MString &setName)
| While the source of geometry parameters is usually configured by the artist through Maya's user interface, this method allows you to programatically set the source of a geometry parameter, including both the data type (e.g.
unsigned int | getElementSize () const
| Get the size in bytes of one element of this parameter.
unsigned int | getMaximumStride () const
| Get the maximum stride of this parameter in bytes.
MStatus | addElement (const MVaryingParameter &child)
| Add a child element to this parameter.
unsigned int | numElements () const
| Get the number of elements in this structure.
MVaryingParameter | getElement (unsigned int i) const
| Get an element within a structure.
MStatus | removeElements ()
| Remove all child elements from a structure.
unsigned int | getUpdateId () const
| Get the update id.
## Friends
class | MVaryingParameterList Search for all occurrences

## Member Enumeration Documentation

enum MVaryingParameterType

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Parameter types.

Enumerator:

  kInvalidParameter | Search for all occurrences
  kStructure | Search for all occurrences
  kFloat | Search for all occurrences

enum MVaryingParameterSemantic

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Parameter semantics (i.e. what the parameter represents).

Enumerator:

  kNoSemantic | Search for all occurrences
  kPosition | Search for all occurrences
  kNormal | Search for all occurrences
  kTexCoord | Search for all occurrences
  kColor | Search for all occurrences
  kWeight | Search for all occurrences
  kTangent | Search for all occurrences
  kBinormal | Search for all occurrences

## Constructor & Destructor Documentation

MVaryingParameter | ( |  | ) |

Create an uninitialised (i.e.

NULL) varying parameter.

MVaryingParameter | ( | const MString & | name,
|  | MVaryingParameterType | type,
|  | int | minDimension = `1`,
|  | int | maxDimension = `1`,
|  | MVaryingParameterSemantic | semantic = `kNoSemantic`,
|  | bool | invertTexCoords = `false`,
|  | const MString & | semanticName = `""`
| ) |  |

Create a new varying parameter.

Parameters:

  [in] | name | the name of the new parameter. For independently configurable inputs, this must be unique across all parameters on the shader. If multiple parameters share the same name, only a single input will be presented to the user, and the value used to populate the set of commonly named parameters.
  [in] | type | the type of the new parameter. This can either be an atomic type (e.g. float), or a structure containing other parameters. Vectors of atomic types (e.g. float4) are defined by setting the atomic type to kFloat, and specifying the maxDimension value (e.g. 4).
  [in] | minDimension | specifies the minimum vector dimension of the specified atomic type that should be used to populate this parameter. Many hardware channels allow binding of a variable number of elements per value; for example you can bind a stream of float3s or float4s to a color register. In this case, you would specify a minDimension value of 3, and a maxDimension value of 4. This value is ignored for structures and elements inside structures (elements inside a structure are always maxDimension size).
  [in] | maxDimension | specifies the maximum vector dimension of the specified atomic type that should be used to populate this parameter. See minDimension for more information. This value is ignored for structures.
  [in] | semantic | specifies the expected usage of the paramter (e.g. we expect this to be a colour, or a tangent, etc). This gives Maya a hint as to how the input should be presented to the user, and possibly even which input data is valid for this parameter. This value is ignored for structures.
  [in] | invertTexCoords | If true the V texture coordinate will be inverted, so that it begins at the top of the texture rather than the bottom.
  [in] | semanticName | The semanticName is used to identify a custom vertex stream request in order to fill the stream with the appropriate data requested by a shader override.

MVaryingParameter | ( | const MString & | name,
|  | MVaryingParameterType | type,
|  | int | minDimension,
|  | int | maxDimension,
|  | int | dimension,
|  | MVaryingParameterSemantic | semantic = `kNoSemantic`,
|  | const MString & | destinationSet = `""`,
|  | bool | invertTexCoords = `false`,
|  | const MString & | semanticName = `""`
| ) |  |

Create a new varying parameter.

Parameters:

  [in] | name | the name of the new parameter. For independently configurable inputs, this must be unique across all parameters on the shader. If multiple parameters share the same name, only a single input will be presented to the user, and the value used to populate the set of commonly named parameters.
  [in] | type | the type of the new parameter. This can either be an atomic type (e.g. float), or a structure containing other parameters. Vectors of atomic types (e.g. float4) are defined by setting the atomic type to kFloat, and specifying the maxDimension value (e.g. 4).
  [in] | minDimension | specifies the minimum vector dimension of the specified atomic type that should be used to populate this parameter. Many hardware channels allow binding of a variable number of elements per value; for example you can bind a stream of float3s or float4s to a color register. In this case, you would specify a minDimension value of 3, and a maxDimension value of 4. This value is ignored for structures and elements inside structures (elements inside a structure are always maxDimension size).
  [in] | maxDimension | specifies the maximum vector dimension of the specified atomic type that should be used to populate this parameter. See minDimension for more information. This value is ignored for structures.
  [in] | dimension | specifies the preferred dimension of the specified atomic type that should be used to populate this parameter. This value is ignored for structures.
  [in] | semantic | specifies the expected usage of the paramter (e.g. we expect this to be a colour, or a tangent, etc). This gives Maya a hint as to how the input should be presented to the user, and possibly even which input data is valid for this parameter. This value is ignored for structures.
  [in] | destinationSet | specifies the name of the destination data sets (e.g. uv sets 1,2,3,... color sets) we would like this Varying parameter bound to. For instance we could have a kTexCoord semantic with a destination data set of "map2" that would bind to the second uv corrdinate set. Ignored for Vertex and Normals.
  [in] | invertTexCoords | If true the V texture coordinate will be inverted, so that it begins at the top of the texture rather than the bottom.
  [in] | semanticName | The semanticName is used to identify a custom vertex stream request in order to fill the stream with the appropriate data requested by a shader override.

## Member Function Documentation

const MVaryingParameter & operator= | ( | const MVaryingParameter & | src | ) |

Assignment operator.

Parameters:

  [in] | src | Right operand.

const MString name | ( |  | ) | const

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Get the name of this parameter.

Returns:
  The name of this parameter

Examples:
  hlslShader.cpp.

MVaryingParameter::MVaryingParameterType type | ( |  | ) | const

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Get the type of this parameter.

Returns:
  The type of this parameter

MVaryingParameter::MVaryingParameterSemantic semantic | ( |  | ) | const

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Get the semantic of this parameter.

Returns:
  The semantic of this parameter

Examples:
  hlslShader.cpp.

const MString semanticName | ( |  | ) | const

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Get the semantic name assigned to this parameter The semanticName is used to identify a custom vertex stream request in order to fill the stream with the appropriate data requested by a shader override.

Returns:
  The semantic name of this parameter

MString destinationSet | ( |  | ) | const

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Get the destination Set of this parameter.

Returns:
  The destination Set of this parameter

int dimension | ( |  | ) | const

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Get the dimension of this parameter.

Returns:
  The dimension of this parameter

MStatus getBuffer | ( | MGeometry & | geometry,
|  | const void *& | data,
|  | unsigned int & | elements,
|  | unsigned int & | count
| ) |  | const

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Get the data for this parameter as a system memory buffer.

Parameters:

  [in] | geometry | the geometry cache the data should be retrieved from. This corresponds to the shape (e.g. mesh) you want the data for.
  [out] | data | returns a pointer to the data (or NULL if the parameter is not available).
  [in] | elements | the number of elements specified for this parameter (e.g. is it 3 floats or 4 floats?)
  [in] | count | the number of values returned for this parameter (e.g. there are 426 normals)

Returns:
  - MS::kFailure if the parameter could not be retrieved.
  - MS::kSuccess otherwise.

MVaryingParameter::MVaryingParameterSemantic getSourceType | ( |  | ) | const

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Get the type of data (e.g.

position, normal, uv) currently populating this parameter. This method will only return a useful value when called on leaf-level parameters (e.g. structures do not have sources, only the elements of a structure have sources).

Returns:
  The current data type populating of this parameter

MString getSourceSetName | ( |  | ) | const

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If the current data type supports data sets (e.g.

uv sets, color sets), get the name of the data set populating this parameter. This method will only return a useful value when called on leaf-level parameters (e.g. structures do not have sources, only the elements of a structure have sources).

Returns:
  The current source set of this parameter

MStatus setSource | ( | MVaryingParameter::MVaryingParameterSemantic | type,
|  | const MString & | setName
| ) |  |

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While the source of geometry parameters is usually configured by the artist through Maya's user interface, this method allows you to programatically set the source of a geometry parameter, including both the data type (e.g.

position, normal, etc) and an optional set name (e.g. UV set "map1"). This is useful for implementing custom default values or shader operations.

Parameters:

  [in] | type | the type of data to populate this parameter with
  [in] | setName | the specific data set to use for parameter types which support data sets, such as UV and color.

Returns:
  - MS::kFailure if the source could not be set (e.g. the parameter is invalid).
  - MS::kSuccess otherwise.

unsigned int getElementSize | ( |  | ) | const

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Get the size in bytes of one element of this parameter.

Returns:
  The size in bytes of one element of this parameter.

unsigned int getMaximumStride | ( |  | ) | const

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Get the maximum stride of this parameter in bytes.

For parameter that accept a range of element counts, this corresponds to the maximum number of elements the parameter supports.

Returns:
  The maximum stride of this parameter in bytes.

MStatus addElement | ( | const MVaryingParameter & | child | ) |

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Add a child element to this parameter.

This operation is only valid for parameters of type kStructure.

Parameters:

  [in] | child | the parameter to add to the structure.

Returns:
  - MS::kFailure if an error occured (e.g. the parameter is not a structure)
  - MS::kSuccess otherwise.

unsigned int numElements | ( |  | ) | const

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Get the number of elements in this structure.

This operation is only valid for parameters of type kStructure.

Returns:
  The number of elements in this structure.

Examples:
  hlslShader.cpp.

MVaryingParameter getElement | ( | unsigned int | i | ) | const

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Get an element within a structure.

This operation is only valid for parameters of type kStructure.

Parameters:

  [in] | i | The index of the structure element to return.

Returns:
  The structure element. This will be a NULL element if an invalid index was specified.

Examples:
  hlslShader.cpp.

MStatus removeElements | ( |  | ) |

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Remove all child elements from a structure.

This operation is only valid for parameters of type kStructure.

Returns:
  - MS::kFailure if an error occured (e.g. the parameter is not a structure)
  - MS::kSuccess otherwise.

unsigned int getUpdateId | ( |  | ) | const

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Get the update id.

The update id is increased every time the parameter sources or sourceSet are changed. A plugin can compare the update id value between subsequent calls to this function to know if the source has changed since the last call.

Returns:
  The update id

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