btHeightfieldTerrainShape simulates a 2D heightfield terrain More...

#include <btHeightfieldTerrainShape.h>

Inheritance diagram for btHeightfieldTerrainShape:

Public Member Functions
	btHeightfieldTerrainShape (int heightStickWidth, int heightStickLength, void *heightfieldData, btScalar heightScale, btScalar minHeight, btScalar maxHeight, int upAxis, PHY_ScalarType heightDataType, bool flipQuadEdges)
	preferred constructor
	btHeightfieldTerrainShape (int heightStickWidth, int heightStickLength, void *heightfieldData, btScalar maxHeight, int upAxis, bool useFloatData, bool flipQuadEdges)
	legacy constructor
virtual	~btHeightfieldTerrainShape ()
void	setUseDiamondSubdivision (bool useDiamondSubdivision=true)
virtual void	getAabb (const btTransform &t, btVector3 &aabbMin, btVector3 &aabbMax) const
	getAabb returns the axis aligned bounding box in the coordinate frame of the given transform t.
virtual void	processAllTriangles (btTriangleCallback *callback, const btVector3 &aabbMin, const btVector3 &aabbMax) const
	process all triangles within the provided axis-aligned bounding box
virtual void	calculateLocalInertia (btScalar mass, btVector3 &inertia) const
virtual void	setLocalScaling (const btVector3 &scaling)
virtual const btVector3 &	getLocalScaling () const
virtual const char *	getName () const
Protected Member Functions
virtual btScalar	getRawHeightFieldValue (int x, int y) const
void	quantizeWithClamp (int *out, const btVector3 &point, int isMax) const
	given input vector, return quantized version
void	getVertex (int x, int y, btVector3 &vertex) const
	this returns the vertex in bullet-local coordinates
void	initialize (int heightStickWidth, int heightStickLength, void *heightfieldData, btScalar heightScale, btScalar minHeight, btScalar maxHeight, int upAxis, PHY_ScalarType heightDataType, bool flipQuadEdges)
	protected initialization
Protected Attributes
btVector3	m_localAabbMin
btVector3	m_localAabbMax
btVector3	m_localOrigin
int	m_heightStickWidth
	terrain data
int	m_heightStickLength
btScalar	m_minHeight
btScalar	m_maxHeight
btScalar	m_width
btScalar	m_length
btScalar	m_heightScale
union {
unsigned char * m_heightfieldDataUnsignedChar
short * m_heightfieldDataShort
btScalar * m_heightfieldDataFloat
void * m_heightfieldDataUnknown
};
PHY_ScalarType	m_heightDataType
bool	m_flipQuadEdges
bool	m_useDiamondSubdivision
int	m_upAxis
btVector3	m_localScaling

Detailed Description

btHeightfieldTerrainShape simulates a 2D heightfield terrain

The caller is responsible for maintaining the heightfield array; this class does not make a copy.

The heightfield can be dynamic so long as the min/max height values capture the extremes (heights must always be in that range).

The local origin of the heightfield is assumed to be the exact center (as determined by width and length and height, with each axis multiplied by the localScaling).

NOTE: be careful with coordinates. If you have a heightfield with a local min height of -100m, and a max height of +500m, you may be tempted to place it at the origin (0,0) and expect the heights in world coordinates to be -100 to +500 meters. Actually, the heights will be -300 to +300m, because bullet will re-center the heightfield based on its AABB (which is determined by the min/max heights). So keep in mind that once you create a btHeightfieldTerrainShape object, the heights will be adjusted relative to the center of the AABB. This is different to the behavior of many rendering engines, but is useful for physics engines.

Most (but not all) rendering and heightfield libraries assume upAxis = 1 (that is, the y-axis is "up"). This class allows any of the 3 coordinates to be "up". Make sure your choice of axis is consistent with your rendering system.

The heightfield heights are determined from the data type used for the heightfieldData array.

PHY_UCHAR: height at a point is the uchar value at the grid point, multipled by heightScale. uchar isn't recommended because of its inability to deal with negative values, and low resolution (8-bit).

PHY_SHORT: height at a point is the short int value at that grid point, multipled by heightScale.

PHY_FLOAT: height at a point is the float value at that grid point. heightScale is ignored when using the float heightfield data type.

Whatever the caller specifies as minHeight and maxHeight will be honored. The class will not inspect the heightfield to discover the actual minimum or maximum heights. These values are used to determine the heightfield's axis-aligned bounding box, multiplied by localScaling.

For usage and testing see the TerrainDemo.

Definition at line 71 of file btHeightfieldTerrainShape.h.

Constructor & Destructor Documentation

btHeightfieldTerrainShape::btHeightfieldTerrainShape	(	int	heightStickWidth,
		int	heightStickLength,
		void *	heightfieldData,
		btScalar	heightScale,
		btScalar	minHeight,
		btScalar	maxHeight,
		int	upAxis,
		PHY_ScalarType	heightDataType,
		bool	flipQuadEdges
	)

preferred constructor

This constructor supports a range of heightfield data types, and allows for a non-zero minimum height value. heightScale is needed for any integer-based heightfield data types.

Definition at line 23 of file btHeightfieldTerrainShape.cpp.

References iTaSC::initialize().

btHeightfieldTerrainShape::btHeightfieldTerrainShape	(	int	heightStickWidth,
		int	heightStickLength,
		void *	heightfieldData,
		btScalar	maxHeight,
		int	upAxis,
		bool	useFloatData,
		bool	flipQuadEdges
	)

legacy constructor

The legacy constructor assumes the heightfield has a minimum height of zero. Only unsigned char or floats are supported. For legacy compatibility reasons, heightScale is calculated as maxHeight / 65535 (and is only used when useFloatData = false).

Definition at line 36 of file btHeightfieldTerrainShape.cpp.

References initialize(), PHY_FLOAT, and PHY_UCHAR.

btHeightfieldTerrainShape::~btHeightfieldTerrainShape ( ) [virtual]

Definition at line 122 of file btHeightfieldTerrainShape.cpp.

Member Function Documentation

void btHeightfieldTerrainShape::calculateLocalInertia	(	btScalar	mass,
		btVector3 &	inertia
	)		const `[virtual]`

Implements btCollisionShape.

Definition at line 397 of file btHeightfieldTerrainShape.cpp.

void btHeightfieldTerrainShape::getAabb	(	const btTransform &	t,
		btVector3 &	aabbMin,
		btVector3 &	aabbMax
	)		const `[virtual]`

getAabb returns the axis aligned bounding box in the coordinate frame of the given transform t.

Implements btCollisionShape.

Definition at line 128 of file btHeightfieldTerrainShape.cpp.

References btMatrix3x3::absolute(), dot(), btTransform::getBasis(), btConcaveShape::getMargin(), btTransform::getOrigin(), m_localAabbMax, m_localAabbMin, m_localScaling, m_maxHeight, m_minHeight, and m_upAxis.

const btVector3 & btHeightfieldTerrainShape::getLocalScaling ( ) const [virtual]

Implements btCollisionShape.

Definition at line 408 of file btHeightfieldTerrainShape.cpp.

References m_localScaling.

virtual const char* btHeightfieldTerrainShape::getName ( void ) const [inline, virtual]

Implements btCollisionShape.

Definition at line 157 of file btHeightfieldTerrainShape.h.

btScalar btHeightfieldTerrainShape::getRawHeightFieldValue	(	int	x,
		int	y
	)		const `[protected, virtual]`

This returns the "raw" (user's initial) height, not the actual height. The actual height needs to be adjusted to be relative to the center of the heightfield's AABB.

Definition at line 152 of file btHeightfieldTerrainShape.cpp.

References btAssert, m_heightDataType, m_heightfieldDataFloat, m_heightfieldDataShort, m_heightfieldDataUnsignedChar, m_heightScale, m_heightStickWidth, PHY_FLOAT, PHY_SHORT, PHY_UCHAR, and simple_enum_gen::val.

Referenced by getVertex().

void btHeightfieldTerrainShape::getVertex	(	int	x,
		int	y,
		btVector3 &	vertex
	)		const `[protected]`

this returns the vertex in bullet-local coordinates

Definition at line 190 of file btHeightfieldTerrainShape.cpp.

References btAssert, getRawHeightFieldValue(), m_heightStickLength, m_heightStickWidth, m_length, m_localOrigin, m_localScaling, m_upAxis, and m_width.

Referenced by processAllTriangles().

void btHeightfieldTerrainShape::initialize	(	int	heightStickWidth,
		int	heightStickLength,
		void *	heightfieldData,
		btScalar	heightScale,
		btScalar	minHeight,
		btScalar	maxHeight,
		int	upAxis,
		PHY_ScalarType	heightDataType,
		bool	flipQuadEdges
	)		`[protected]`

protected initialization

Handles the work of constructors so that public constructors can be backwards-compatible without a lot of copy/paste.

Definition at line 55 of file btHeightfieldTerrainShape.cpp.

References btAssert, PHY_FLOAT, PHY_SHORT, PHY_UCHAR, and TERRAIN_SHAPE_PROXYTYPE.

Referenced by btHeightfieldTerrainShape().

void btHeightfieldTerrainShape::processAllTriangles	(	btTriangleCallback *	callback,
		const btVector3 &	aabbMin,
		const btVector3 &	aabbMax
	)		const `[virtual]`

process all triangles within the provided axis-aligned bounding box

basic algorithm:

convert input aabb to local coordinates (scale down and shift for local origin)
convert input aabb to a range of heightfield grid points (quantize)
iterate over all triangles in that subset of the grid

Implements btConcaveShape.

Definition at line 284 of file btHeightfieldTerrainShape.cpp.

References btAssert, getVertex(), i, m_flipQuadEdges, m_heightStickLength, m_heightStickWidth, m_localOrigin, m_localScaling, m_upAxis, m_useDiamondSubdivision, btTriangleCallback::processTriangle(), and quantizeWithClamp().

void btHeightfieldTerrainShape::quantizeWithClamp	(	int *	out,
		const btVector3 &	point,
		int	isMax
	)		const `[protected]`

given input vector, return quantized version

This routine is basically determining the gridpoint indices for a given input vector, answering the question: "which gridpoint is closest to the provided point?".

"with clamp" means that we restrict the point to be in the heightfield's axis-aligned bounding box.

Definition at line 263 of file btHeightfieldTerrainShape.cpp.

References getQuantized(), m_localAabbMax, and m_localAabbMin.

Referenced by processAllTriangles().

void btHeightfieldTerrainShape::setLocalScaling ( const btVector3 & scaling ) [virtual]

Implements btCollisionShape.

Definition at line 404 of file btHeightfieldTerrainShape.cpp.

References m_localScaling.

void btHeightfieldTerrainShape::setUseDiamondSubdivision ( bool useDiamondSubdivision = true ) [inline]

Definition at line 143 of file btHeightfieldTerrainShape.h.

References m_useDiamondSubdivision.