GrassyTerrain Class Reference

#include <src/GrassyTerrain.h>

Inheritance diagram for GrassyTerrain:

[legend]Collaboration diagram for GrassyTerrain:

[legend]List of all members.

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Detailed Description

Adds grass to the terrain.

Grass is modelled as an energy density per surface. It can grow with a given rate, and be eaten.

Author:

Nicolas Brodu

Public Member Functions
	GrassyTerrain (double worldSize, double maxHeight, int level, double persistance=0.5, double power=1.0)
virtual double	getGrassDensity (const double x, const double y)
	Gets the current grass density at the given location.
virtual double	getNormalizedGrassDensity (const double x, const double y)
	Same as above, but normalized between 0 and 1.
virtual double	graze (const double x, const double y, const double amount)
	Tries to eat a certain amount of grass at the given location the real amount eaten, if the desired amount is more than the current grass density.
void	setMaximumGrassDensity (const double density)
	Maximum grass density = maximum energy per terrain square unit. Note this is really per square unit, whatever the discretization of the grid: It uses the worldsize argument in the constructor, not the level one. Default is a completely arbitrary 10.0.
double	getMaximumGrassDensity ()
void	setGrassDensity (const double density)
	Give an initial grass density. Default is 5.0.
void	setGrassGrowthRate (const double rate)
	The rate at which grass regenerates, in density per time unit. This is constant growth, not exponential, and clamped at MaximumGrassDensity. Default is a completely arbitrary 1.0.
double	getGrassGrowthRate ()
virtual void	scheduleForGrowth (double integrationTimeStep)
Protected Member Functions
virtual void	grow ()
	Integration step: grass grows till.
virtual void	updateColors ()
	update the colors, but only when necessary (no useless polling)
Protected Attributes
double *	grass
double *	grassEnd
double	maximumGrassDensity
double	maximumGrassDensityPerGridPoint
double	invMaximumGrassDensityPerGridPoint
double	grassGrowthRate
double	grassGrowthRatePerGridPoint
double	timeStep
double	gcoef
bool	cleanVisualState

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Member Function Documentation

double GrassyTerrain::getGrassDensity (  const double  x, const double  y )  [virtual]

Gets the current grass density at the given location. The grass is considered a discrete grid, like for numerical integration. Unlike altitude (in parent Terrain), the grass density is not interpolated. Instead, the closest discrete grid cell is used. The reason for this is to avoid problems when eating the grass: Example: Suppose a request is made for a point C between A and B, with respective distance ratio 2/5 and 3/5. Now suppose we interpolate the values at A=2 and B=7. Then C would have interpolated value of 4. Now an agent request to eat 4 grass units at C. How do we split this request among the points A & B? Suppose we remove some amount from both A and B. Then since neither A and B can be negative, the value at C will be positive too. Thus, after removing 4 units at a place where the agent saw 4 units, grass still remains... till both A and B are consumed entirely, for a grand total of 9 units, thus miserably destroying the initial intent of the interpolation. Using only the closest value corrects this problem, and is consistent with numerical integration schemes anyway.

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

• GrassyTerrain.h
• GrassyTerrain.cpp

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