Substance Class Reference

Physical substance definition, used for collision detection/treatment What we need is mu, slip and kp,kd parameter for the collision Definition of substance parameters: More...

#include <substance.h>

Inherited by DebugSubstance.

List of all members.

Public Member Functions
	Substance ()
	Substance (float roughness, float slip, float hardness, float elasticity)
void	setCollisionCallback (CollisionCallback func, void *userdata)
void	toDefaultSubstance ()
void	toMetal (float roughness)
	very hard and elastic with slip roughness [0.1-1]
void	toRubber (float hardness)
	high roughness, no slip, very elastic, hardness : [5-50]
void	toPlastic (float roughness)
	medium slip, a bit elastic, medium hardness, roughness [0.5-2]
void	toFoam (float _hardness)
	large slip, not elastic, low hardness [1-30], high roughness
void	toSnow (float _slip)
	variable slip and roughness, not elastic, high hardness for solid snow slip = 1 <--> roughness=0.0, slip = 0 <--> roughnes=1.0
void	toNoContact ()
	set the collsion callback to ignores everything Usually it is better to use the "ignorePairs" from odeHandle but if this particular one substance should not collide with any other, this is easier.
void	toAnisotropFriction (double ratio, const Axis &axis)
	enables anisotrop friction.
Static Public Member Functions
static void	getSurfaceParams (dSurfaceParameters &sp, const Substance &s1, const Substance &s2, double stepsize)
	Combination of two surfaces.
static void	printSurfaceParams (const dSurfaceParameters &surfParams)
static Substance	getDefaultSubstance ()
	default substance is plastic with roughness=0.8
static Substance	getMetal (float roughness)
	very hard and elastic with slip roughness [0.1-1]
static Substance	getRubber (float hardness)
	high roughness, no slip, very elastic, hardness : [5-50]
static Substance	getPlastic (float roughness)
	medium slip, a bit elastic, medium hardness, roughness [0.5-2]
static Substance	getFoam (float _hardness)
	large slip, not elastic, low hardness [1-30], high roughness
static Substance	getSnow (float _slip)
	variable slip and roughness [0-1], not elastic, high hardness for solid snow slip = 1 <--> roughness=0.0, slip = 0 <--> roughnes=1.0
static Substance	getNoContact ()
Public Attributes
float	roughness
float	slip
float	hardness
float	elasticity
CollisionCallback	callback
void *	userdata

Detailed Description

Physical substance definition, used for collision detection/treatment What we need is mu, slip and kp,kd parameter for the collision Definition of substance parameters:

       Parameter    interval  collision_parameter
       roughness:  [0-]      mu   = roughness1*roughness2 
       slip:       [0-]      slip = slip1+slip2
       hardness:   [0-]      kp   = hardness1 * hardness2 / (hardness1 + hardness2) (two springs serial)
       elasticity: [0-1]     kd   = (1-elasticity1) * s2.hardness + (1-elasticity2) * s1.hardness) / 
                                    (s1.hardness + s2.hardness);

For the calculation of the spring/damping constant we use the following schema: The collision can be considered as 2 springs serially connected. The spring constant of each collision side is given by hardness (here kp). The spring constant of the entire spring is given by

$1/kp = 1/kp_1 + 1/kp_2$

. The damping (kd) is derived from the elasticity (e), but it is more difficult to compute. Consider the damping in form of energy lost. We can write the energy or work done by each spring as:

$W_i = F*s_i = F^2/p$

with

$s_i=F*kp_i$

. The energy lost though damping is

$W_1^D = W_i*(1-e_i)$

. The final damping is now:

$kd = (1-e) = W^D/W = \frac{(1-e_1)/kp_1 + (1-e_2)/kp_2}{1/kp_1 + 1/kp_2} = \frac{(1-e_1)kp_2 + (1-e_2)kp_1}{kp_1+kp_2}$

.

Note that you cannot add any member variables to derived classes since they do not fit into the substance object in OdeHandle!

Constructor & Destructor Documentation

Substance ( )

Substance	(	float	roughness,
		float	slip,
		float	hardness,
		float	elasticity
	)

Member Function Documentation

Substance getDefaultSubstance ( ) [static]

default substance is plastic with roughness=0.8

Substance getFoam ( float _hardness ) [static]

large slip, not elastic, low hardness [1-30], high roughness

Substance getMetal ( float roughness ) [static]

very hard and elastic with slip roughness [0.1-1]

Substance getNoContact ( ) [static]

See also:: toNoContact()

Substance getPlastic ( float roughness ) [static]

medium slip, a bit elastic, medium hardness, roughness [0.5-2]

Substance getRubber ( float hardness ) [static]

high roughness, no slip, very elastic, hardness : [5-50]

Substance getSnow ( float _slip ) [static]

variable slip and roughness [0-1], not elastic, high hardness for solid snow slip = 1 <--> roughness=0.0, slip = 0 <--> roughnes=1.0

void getSurfaceParams	(	dSurfaceParameters &	sp,
		const Substance &	s1,
		const Substance &	s2,
		double	stepsize
	)			`[static]`

Combination of two surfaces.

void printSurfaceParams ( const dSurfaceParameters & surfParams ) [static]

void setCollisionCallback	(	CollisionCallback	func,
		void *	userdata
	)

void toAnisotropFriction	(	double	ratio,
		const Axis &	axis
	)

enables anisotrop friction.

The friction along the given axis is ratio fold of the friction in the other directions. If ratio = 0.1 and axis=Axis(0,0,1) then the fiction along the z-axis is 1/10th of the normal friction. Useful to mimic scales of snakes or the like. WARNING: this sets the collisionCallback! To disable the collisionCallback has to set to 0 manually

void toDefaultSubstance ( )

void toFoam ( float _hardness )

large slip, not elastic, low hardness [1-30], high roughness

void toMetal ( float roughness )

very hard and elastic with slip roughness [0.1-1]

void toNoContact ( )

set the collsion callback to ignores everything Usually it is better to use the "ignorePairs" from odeHandle but if this particular one substance should not collide with any other, this is easier.

WARNING: this sets the collisionCallback. This will not convert to other substances without manually setting the callback to 0

void toPlastic ( float roughness )

medium slip, a bit elastic, medium hardness, roughness [0.5-2]

void toRubber ( float hardness )

high roughness, no slip, very elastic, hardness : [5-50]

void toSnow ( float _slip )

variable slip and roughness, not elastic, high hardness for solid snow slip = 1 <--> roughness=0.0, slip = 0 <--> roughnes=1.0