Ogre::TangentSpaceCalc Class Reference

Class for calculating a tangent space basis. More...

#include <OgreTangentSpaceCalc.h>

Classes
struct	IndexRemap
	Information about a remapped index. More...
struct	Result
	The result of having built a tangent space basis. More...

Public Types
typedef std::list< IndexRemap >	IndexRemapList
	List of indexes that were remapped (split vertices). More...
typedef std::pair< size_t, size_t >	VertexSplit
typedef std::list< VertexSplit >	VertexSplits

Public Member Functions
	TangentSpaceCalc ()
void	addIndexData (IndexData *i_in, RenderOperation::OperationType opType=RenderOperation::OT_TRIANGLE_LIST)
	Add a set of index data that references the vertex data. More...
Result	build (VertexElementSemantic targetSemantic=VES_TANGENT, unsigned short sourceTexCoordSet=0, unsigned short index=1)
	Build a tangent space basis from the provided data. More...
void	clear ()
	Reset the calculation object. More...
bool	getSplitMirrored () const
	Gets whether or not to split vertices when a mirrored tangent space transition is detected. More...
bool	getSplitRotated () const
	Sets whether or not to split vertices when tangent space rotates more than 90 degrees around a vertex. More...
bool	getStoreParityInW () const
	Gets whether to store tangent space parity in the W of a 4-component tangent or not. More...
void	setSplitMirrored (bool split)
	Sets whether or not to split vertices when a mirrored tangent space transition is detected (matrix parity differs). More...
void	setSplitRotated (bool split)
	Sets whether or not to split vertices when tangent space rotates more than 90 degrees around a vertex. More...
void	setStoreParityInW (bool enabled)
	Sets whether to store tangent space parity in the W of a 4-component tangent or not. More...
void	setVertexData (VertexData *v_in)
	Set the incoming vertex data (which will be modified) More...

Detailed Description

Class for calculating a tangent space basis.

Member Typedef Documentation

VertexSplit

typedef std::pair<size_t, size_t> Ogre::TangentSpaceCalc::VertexSplit

IndexRemapList

typedef std::list<IndexRemap> Ogre::TangentSpaceCalc::IndexRemapList

List of indexes that were remapped (split vertices).

VertexSplits

typedef std::list<VertexSplit> Ogre::TangentSpaceCalc::VertexSplits

Constructor & Destructor Documentation

TangentSpaceCalc()

Ogre::TangentSpaceCalc::TangentSpaceCalc

(

)

Member Function Documentation

clear()

void Ogre::TangentSpaceCalc::clear

(

)

Reset the calculation object.

setVertexData()

void Ogre::TangentSpaceCalc::setVertexData

(

VertexData *

v_in

)

Set the incoming vertex data (which will be modified)

addIndexData()

void Ogre::TangentSpaceCalc::addIndexData	(	IndexData *	i_in,
		RenderOperation::OperationType	opType = RenderOperation::OT_TRIANGLE_LIST
	)

Add a set of index data that references the vertex data.

This might be modified if there are vertex splits.

setStoreParityInW()

void Ogre::TangentSpaceCalc::setStoreParityInW ( bool  enabled )

inline

Sets whether to store tangent space parity in the W of a 4-component tangent or not.

Remarks

The default element format to use is VET_FLOAT3 which is enough to accurately deal with tangents that do not involve any texture coordinate mirroring. If you wish to allow UV mirroring in your model, you must enable 4-component tangents using this method, and the 'w' co-ordinate will be populated with the parity of the triangle (+1 or -1), which will allow you to generate the bitangent properly.

Parameters

enabled

true to enable 4-component tangents (default false). If you enable this, you will probably also want to enable mirror splitting (see setSplitMirrored), and your shader must understand how to deal with the parity.

getStoreParityInW()

bool Ogre::TangentSpaceCalc::getStoreParityInW ( ) const

inline

Gets whether to store tangent space parity in the W of a 4-component tangent or not.

setSplitMirrored()

void Ogre::TangentSpaceCalc::setSplitMirrored ( bool  split )

inline

Sets whether or not to split vertices when a mirrored tangent space transition is detected (matrix parity differs).

Remarks

This defaults to 'off' because it's the safest option; tangents will be interpolated in all cases even if they don't agree around a vertex, so artefacts will be smoothed out. When you're using art assets of unknown quality this can avoid extra seams on the visible surface. However, if your artists are good, they will be hiding texture seams in folds of the model and thus you can turn this option on, which will prevent the results of those seams from getting smoothed into other areas, which is exactly what you want.

Note

This option is automatically disabled if you provide any strip or fan based geometry.

getSplitMirrored()

bool Ogre::TangentSpaceCalc::getSplitMirrored ( ) const

inline

Gets whether or not to split vertices when a mirrored tangent space transition is detected.

setSplitRotated()

void Ogre::TangentSpaceCalc::setSplitRotated ( bool  split )

inline

Sets whether or not to split vertices when tangent space rotates more than 90 degrees around a vertex.

Remarks

This defaults to 'off' because it's the safest option; tangents will be interpolated in all cases even if they don't agree around a vertex, so artefacts will be smoothed out. When you're using art assets of unknown quality this can avoid extra seams on the visible surface. However, if your artists are good, they will be hiding texture inconsistencies in folds of the model and thus you can turn this option on, which will prevent the results of those seams from getting smoothed into other areas, which is exactly what you want.

Note

This option is automatically disabled if you provide any strip or fan based geometry.

getSplitRotated()

bool Ogre::TangentSpaceCalc::getSplitRotated ( ) const

inline

Sets whether or not to split vertices when tangent space rotates more than 90 degrees around a vertex.

References Ogre::TangentSpaceCalc::IndexRemap::faceIndex, Ogre::TangentSpaceCalc::Result::indexesRemapped, Ogre::TangentSpaceCalc::IndexRemap::indexSet, Ogre::TangentSpaceCalc::IndexRemap::splitVertex, and Ogre::VES_TANGENT.

build()

Result Ogre::TangentSpaceCalc::build	(	VertexElementSemantic	targetSemantic = VES_TANGENT,
		unsigned short	sourceTexCoordSet = 0,
		unsigned short	index = 1
	)

Build a tangent space basis from the provided data.

Remarks

Only indexed triangle lists are allowed. Strips and fans cannot be supported because it may be necessary to split the geometry up to respect deviances in the tangent space basis better.

Parameters

targetSemantic	The semantic to store the tangents in. Defaults to the explicit tangent binding, but note that this is only usable on more modern hardware (Shader Model 2), so if you need portability with older cards you should change this to a texture coordinate binding instead.
sourceTexCoordSet	The texture coordinate index which should be used as the source of 2D texture coordinates, with which to calculate the tangents.
index	The element index, ie the texture coordinate set which should be used to store the 3D coordinates representing a tangent vector per vertex, if targetSemantic is VES_TEXTURE_COORDINATES. If this already exists, it will be overwritten.

Returns

A structure containing the results of the tangent space build. Vertex data will always be modified but it's also possible that the index data could be adjusted. This happens when mirroring is used on a mesh, which causes the tangent space to be inverted on opposite sides of an edge. This is discontinuous, therefore the vertices have to be split along this edge, resulting in new vertices.

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

• OgreTangentSpaceCalc.h