GPUHydraulicErosionParticle Class Reference

Hydraulic erosion simulation on the GPU. More...

#include <gputerrainsimu.h>

Public Member Functions
	GPUHydraulicErosionParticle ()
	Constructor. Initialize everthing to zero.
	~GPUHydraulicErosionParticle ()
	Destructor. Destroys OpenGl buffers and shader program.
void	Init (const HeightField &hf)
	Initialize the erosion engine from a heightfield. Must be called before any Step().
void	Step (int n)
	Performs N step of hydraulic erosion on the underlying heightfield.
void	SetUniforms (float inertia, float sedimentCapacity, float depositSpeed, float evaporateSpeed, float erodeSpeed, int maxLifetime, int erosionBrushRadius)
	Set the uniforms in the shader.
void	SetUniforms (float depositSpeed, float erosionSpeed, float evaporationSpeed, float randomSedimentation, float randomSedFreq, float randomSedAmp)
	Set the uniforms in the shader.
void	SetUniforms (float depositSpeed, float erosionSpeed, float evaporationSpeed, int erosionBrushRadius, int maxLifeTime)
	Set the uniforms in the shader.
void	SetGlobalSpeed (float globalSpeed)
	Set the global erosion speed uniform which affects both erosion and deposition.
void	SetHardnessAlpha (const ScalarField2 &hardness)
	Set the hardness alpha map in a buffer.
void	UseHardness (bool use=true)
	Flag for using the hardness alpha map or not.
void	SetHardnessFunction (int index)
	Set the hardness function to use in the shader. See function GetHardness in the shader for more details.
void	UsePrecipitation (bool use=true)
	Flag for using the precipitation map or not.
void	SetPrecipitation (const ScalarField2 &precipitation)
	Set the precipitation map.
void	GetData (ScalarField2 &hf)
	Reads back newest bedrock and sediment elevation from the GPU, into initialized scalarfields.
void	GetData (ScalarField2 &bedrock, ScalarField2 &sediments)
	Reads back newest bedrock and sediment elevation from the GPU, into initialized scalarfields. The sediment scalarfield is normalized.
void	GetDataHardness (ScalarField2 &hardness)
	Get hardness data back from the GPU and store it in a scalar field.

Protected Attributes
GLShader	simulationShader
	Compute shader.
GLBuffer	bedrockBuffer
	Bedrock buffer.
GLBuffer	sedimentBuffer
	Sediment buffer.
GLBuffer	randomIndicesBuffer
	Random number buffer. Easier than generating random number on the GPU.
GLBuffer	brushIndicesBuffer
	Compute buffer.
GLBuffer	brushWeightsBuffer
	Compute buffer.
GLOptionalStorageBuffer	hardnessBuffer
	Optional Hardness buffer.
GLBuffer	outHardnessBuffer
	Output hardness buffer (useful if we use the GPU function to generate hardness on the fly)
GLOptionalStorageBuffer	precipitationBuffer
	Precipitation buffer.
int	totalBufferSize
	Total buffer size defined as nx * ny.
int	dispatchSize
	Single dispatch size.
int	nx
	Heightfield dimension.
int	ny
	Heightfield dimension.
double	scaleZa
	Heightfield min elevation.
double	scaleZb
	Heightfield max elevation.
std::vector< int >	randomIndices
	Random indices for the algorithm.
std::vector< float >	tmpData
	Temporary array for retreiving GPU data.

Detailed Description

Hydraulic erosion simulation on the GPU.

The algorithm uses a particle-based approach all simulated independently on the terrain.

The implementation is based on https://github.com/SebLague/Hydraulic-Erosion It has a race condition: multiple threads can be writing to the elevation buffer at the same time, Thus making some operations not taken into account. The original shader suffers from the same issue.

AXEL : this doesn't work anymore, have to figure it out. Weird buffer issue ?

Member Function Documentation

GetDataHardness()

void GPUHydraulicErosionParticle::GetDataHardness

(

ScalarField2 &

hardness

)

Get hardness data back from the GPU and store it in a scalar field.

Parameters

hardness

the returned hardness data

Init()

void GPUHydraulicErosionParticle::Init

(

const HeightField &

hf

)

Initialize the erosion engine from a heightfield. Must be called before any Step().

Parameters

hf	heightfield

SetGlobalSpeed()

void GPUHydraulicErosionParticle::SetGlobalSpeed

(

float

globalSpeed

)

Set the global erosion speed uniform which affects both erosion and deposition.

Parameters

globalSpeed

speed, should be between [0, 1]

SetHardnessAlpha()

void GPUHydraulicErosionParticle::SetHardnessAlpha

(

const ScalarField2 &

hardness

)

Set the hardness alpha map in a buffer.

Parameters

hardness

hardness alpja.

SetHardnessFunction()

void GPUHydraulicErosionParticle::SetHardnessFunction

(

int

index

)

Set the hardness function to use in the shader. See function GetHardness in the shader for more details.

Parameters

index

0 = Simple strata 1 = Warped strata 2 = 3D noise 3 = Faulting The hardness function can be combined with an alpha map

SetPrecipitation()

void GPUHydraulicErosionParticle::SetPrecipitation

(

const ScalarField2 &

precipitation

)

Set the precipitation map.

Parameters

precipitation

the map

SetUniforms() [1/3]

void GPUHydraulicErosionParticle::SetUniforms	(	float	depositSpeed,
		float	erosionSpeed,
		float	evaporationSpeed,
		float	randomSedimentation,
		float	randomSedFreq,
		float	randomSedAmp )

Set the uniforms in the shader.

Parameters

depositSpeed
erosionSpeed
evaporationSpeed
randomSedimentation
randomSedFreq
randomSedAmp

SetUniforms() [2/3]

void GPUHydraulicErosionParticle::SetUniforms	(	float	depositSpeed,
		float	erosionSpeed,
		float	evaporationSpeed,
		int	erosionBrushRadius,
		int	maxLifeTime )

Set the uniforms in the shader.

Parameters

depositSpeed
erosionSpeed
evaporationSpeed
erosionBrushRadius
maxLifeTime

SetUniforms() [3/3]

void GPUHydraulicErosionParticle::SetUniforms	(	float	inertia,
		float	sedimentCapacity,
		float	depositSpeed,
		float	evaporateSpeed,
		float	erodeSpeed,
		int	maxLifetime,
		int	erosionBrushRadius )

Set the uniforms in the shader.

Parameters

inertia
sedimentCapacity
depositSpeed
evaporateSpeed
erodeSpeed
maxLifetime
erosionBrushRadius

Step()

void GPUHydraulicErosionParticle::Step

(

int

n

)

Performs N step of hydraulic erosion on the underlying heightfield.

Parameters

n	step count

UseHardness()

void GPUHydraulicErosionParticle::UseHardness

(

bool

use = true

)

Flag for using the hardness alpha map or not.

Parameters

use

UsePrecipitation()

void GPUHydraulicErosionParticle::UsePrecipitation

(

bool

use = true

)

Flag for using the precipitation map or not.

Parameters

use