Discussion :

[robinsondesbois]

Bonjour,

Je suis en train de travailler sur les systèmes de particules sur GPU. J'ai donc trouvé ce tuto pour effectuer une simulation uniquement sur GPU.
Je pense que je me mélange un peut les pinceaux entre les buffers.

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GLuint transformFeedbackBuffer;
GLuint particleBuffer[2];
GLuint VAO[2];

Il y a deux type de particules, les génératrices et les autres.
D'après l'objet Query, mon nombre de particules augmentent. Le problème c'est que j'en est qu'une qui est affiché si ma première particule génératrice génère des particules normales. Par contre si elle génère des particules de type génératrice, elles sont affiché mais ne subissent pas le feedback.

Voici le geometry shader du tuto pour l'update des particules :
Je l'ai modifié pour qu'il puisse simplement faire monter les particules.

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void main() 
{ 
  vLocalSeed = vRandomSeed; 
 
  // gl_Position doesn't matter now, as rendering is discarded, so I don't set it at all
 
  vPositionOut = vPositionPass[0] + vec3(0.0, 0.01, 0.0); 
  vVelocityOut = vVelocityPass[0]; 
  if(iTypePass[0] != 0)vPositionOut += /*vVelocityOut*fTimePassed + */vec3(0.0, 0.05, 0.0); 
  if(iTypePass[0] != 0)vVelocityOut += vGenGravityVector*fTimePassed; 
 
  vColorOut = vColorPass[0]; 
  fLifeTimeOut = fLifeTimePass[0]-fTimePassed; 
  fSizeOut = fSizePass[0]; 
  iTypeOut = iTypePass[0]; 
 
  if(iTypeOut == 0) 
  { 
    EmitVertex(); 
    EndPrimitive();
 
    for(int i = 0; i < iNumToGenerate; i++) 
    { 
      vPositionOut = vec3(0.0, -1.0, 0.0);
      vVelocityOut = vGenVelocityMin+vec3(vGenVelocityRange.x*randZeroOne(), vGenVelocityRange.y*randZeroOne(), vGenVelocityRange.z*randZeroOne()); 
	  vVelocityOut = vec3(0.0, 0.1, 0.0);
      vColorOut = vGenColor; 
      fLifeTimeOut = fGenLifeMin+fGenLifeRange*randZeroOne(); 
      fSizeOut = fGenSize; 
      iTypeOut = 1; 
      EmitVertex(); 
      EndPrimitive(); 
    } 
  } 
  else /*if(fLifeTimeOut > 0.0) */
  { 
      EmitVertex(); 
      EndPrimitive();  
  } 
}

Si j'ai bien compris, on génère iNumToGenerate particule de type 1 (donc pas génératrice).

Je vous joint mon code. Je doit vous avouer que je ne vois pas d’où viens le problème.

Le point d'entré de cette classe est la fonction apply qui est appelé à chaque frame.

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#ifndef PARTICLESYSTEMTRANSFORMFEEDBACK_H
#define PARTICLESYSTEMTRANSFORMFEEDBACK_H
 
#include <GL/glew.h>
#include <SFML/OpenGL.hpp>
#include <glm.hpp>
 
#include "Shader.h"
#include "GraphicComponant.h"
 
enum PARTICLETYPE
{
	PARTICLE_TYPE_GENERATOR = 0,
	PARTICLE_TYPE_BASIC
};
 
class ParticleTransformFeedback
{
public:
	glm::vec3 vPosition;
	glm::vec3 vVelocity;
	glm::vec3 vColor;
	float fLifeTime;
	float fSize;
	int iType;
};
 
class ParticleSystemTransformFeedback : public GraphicComponant
{
private:
	bool initialized;
	bool first;
	GLuint transformFeedbackBuffer;
	GLuint particleBuffer[2];
	GLuint VAO[2];
 
	GLuint query;
	GLuint texture;
 
	int currentBuffer;
	int nbParticles;
 
	glm::vec3 quad1, quad2;
 
	float previousTime;
	float elapsedTime;
	float nextGenerationTime;
 
	glm::vec3 genPosition;
	glm::vec3 genVelocityMin, genVelocityRange;
	glm::vec3 genGravity;
	glm::vec3 genColor;
 
	float genLifeMin, genLifeRange;
	float genSize;
 
	int nbToGenerate;
 
	Shader* renderShader;
	Shader* updateShader;
 
public:
	ParticleSystemTransformFeedback();
 
	bool initializeParticleSystem();
 
	void renderParticles(GlobalInformation* globalInformation);
	void updateParticles(float timePassed);
 
	void setGeneratorProperty(glm::vec3 genPosition, glm::vec3 genVelocityMin, glm::vec3 genVelocityMax, glm::vec3 genGravityVector, glm::vec3 genColor, 
							  float genLifeMin, float genLifeMax, float genSize, float every, int numToGenerate);
 
	void clearAllParticles();
	bool releaseParticleSystem();
 
	virtual void apply(float time, glm::vec3* position, glm::mat3* rotation, glm::vec3* scale, GlobalInformation* globalInformation);
 
	int getNbParticles();
 
	~ParticleSystemTransformFeedback();
};
 
#endif

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#include "ParticleSystemTransformFeedback.h"
 
ParticleSystemTransformFeedback::ParticleSystemTransformFeedback()
{
	this->initialized = false;
	this->first = true;
	this->currentBuffer = 0;
	setGeneratorProperty(glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(-0.5, 0, -0.5), glm::vec3(0.5, 0.20, 0.5), glm::vec3(0, -0.0, 0), glm::vec3(0.0f, 0.5f, 1.0f), 2000.0f, 3000.0f, 0.05f, 2000.0f, 30);
}
 
bool ParticleSystemTransformFeedback::initializeParticleSystem()
{
	if (this->initialized)
		return false;
 
	const char* sVaryings[6] =  
	{ 
		"vPositionOut", 
		"vVelocityOut", 
		"vColorOut", 
		"fLifeTimeOut", 
		"fSizeOut", 
		"iTypeOut", 
	}; 
 
	this->updateShader = new Shader("../IN55-Project/res/shaders/particles_update.vert", "../IN55-Project/res/shaders/particles_update.geo", "../IN55-Project/res/shaders/particles_update.frag");
	this->renderShader = new Shader("../IN55-Project/res/shaders/particles_render.vert", "../IN55-Project/res/shaders/particles_render.geo", "../IN55-Project/res/shaders/particles_render.frag");
 
	glTransformFeedbackVaryings(this->updateShader->getProgramID(), 6, sVaryings, GL_INTERLEAVED_ATTRIBS);
	this->updateShader->linkProgram();
 
	glGenTransformFeedbacks(1, &this->transformFeedbackBuffer);
	glGenQueries(1, &this->query);
 
	glGenBuffers(2, this->particleBuffer);
	glGenVertexArrays(2, this->VAO);
 
	ParticleTransformFeedback particleInitialisation[10000];
	memset(particleInitialisation, 0, sizeof(particleInitialisation));
	particleInitialisation[0].iType = PARTICLE_TYPE_GENERATOR;
 
	for (int i=0; i<2; ++i)
	{
		glBindVertexArray(this->VAO[i]);
		glBindBuffer(GL_ARRAY_BUFFER, this->particleBuffer[i]);
		glBufferData(GL_ARRAY_BUFFER, sizeof(particleInitialisation), particleInitialisation, GL_DYNAMIC_DRAW);
 
		for (int j=0; j<6; ++j)
			glEnableVertexAttribArray(j);
 
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(ParticleTransformFeedback), (const GLvoid*)0);
		glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(ParticleTransformFeedback), (const GLvoid*)12);
		glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(ParticleTransformFeedback), (const GLvoid*)24);
		glVertexAttribPointer(3, 1, GL_FLOAT, GL_FALSE, sizeof(ParticleTransformFeedback), (const GLvoid*)36);
		glVertexAttribPointer(4, 1, GL_FLOAT, GL_FALSE, sizeof(ParticleTransformFeedback), (const GLvoid*)40);
		glVertexAttribPointer(5, 1, GL_INT,	  GL_FALSE, sizeof(ParticleTransformFeedback), (const GLvoid*)44);
	}
 
	this->currentBuffer = 0;
	this->nbParticles = 1;
 
	this->initialized = true;
 
	return true;
}
 
void ParticleSystemTransformFeedback::renderParticles(GlobalInformation* globalInformation)
{
	if (!this->initialized)
		return;
 
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE);
	glDepthMask(0);
	glDisable(GL_RASTERIZER_DISCARD);
 
	GLuint programID = this->renderShader->getProgramID();
	glUseProgram(programID);
		glUniformMatrix4fv(glGetUniformLocation(programID, "matrices.mView"), 1, GL_FALSE, &globalInformation->getCurrentCamera()->getView()[0][0]);
		glUniformMatrix4fv(glGetUniformLocation(programID, "matrices.mProj"), 1, GL_FALSE, &globalInformation->getCurrentCamera()->getProjection()[0][0]);
		glUniform3f(glGetUniformLocation(programID, "vQuad1"), this->quad1.x, this->quad1.y, this->quad1.z);
		glUniform3f(glGetUniformLocation(programID, "vQuad2"), this->quad2.x, this->quad2.y, this->quad2.z);
 
		glBindVertexArray(this->VAO[this->currentBuffer]);
		glDisableVertexAttribArray(1);
 
		glDrawTransformFeedback(GL_POINTS, this->transformFeedbackBuffer);
 
		glDepthMask(1);
		glDisable(GL_BLEND);
	glUseProgram(0);
}
 
float grandf(float fMin, float fAdd)
{
	float fRandom = float(rand()%(RAND_MAX+1))/float(RAND_MAX);
	return fMin+fAdd*fRandom;
}
 
void ParticleSystemTransformFeedback::updateParticles(float timePassed)
{
	if (!this->initialized)
		return;
 
	GLuint programID = this->updateShader->getProgramID();
	glUseProgram(programID);
		glUniform1f(glGetUniformLocation(programID, "fTimePassed"), timePassed);
		glUniform3f(glGetUniformLocation(programID, "vGenPosition"), this->genPosition.x, this->genPosition.y, this->genPosition.z);
		glUniform3f(glGetUniformLocation(programID, "vGenVelocityMin"), this->genVelocityMin.x, this->genVelocityMin.y, this->genVelocityMin.z);
		glUniform3f(glGetUniformLocation(programID, "vGenVelocityRange"), this->genVelocityRange.x, this->genVelocityRange.y, this->genVelocityRange.z);
		glUniform3f(glGetUniformLocation(programID, "vGenColor"), this->genColor.x, this->genColor.y, this->genColor.z);
		glUniform3f(glGetUniformLocation(programID, "vGenGravityVector"), this->genGravity.x, this->genGravity.y, this->genGravity.z);
 
		glUniform1f(glGetUniformLocation(programID, "fGenLifeMin"), this->genLifeMin);
		glUniform1f(glGetUniformLocation(programID, "fGenLifeRange"), this->genLifeRange);
 
		glUniform1f(glGetUniformLocation(programID, "fGenSize"), this->genSize);
		glUniform1i(glGetUniformLocation(programID, "iNumToGenerate"), 0);
 
		this->elapsedTime += timePassed;
 
		if (this->elapsedTime > this->nextGenerationTime)
		{
			glUniform1i(glGetUniformLocation(programID, "iNumToGenerate"), this->nbToGenerate);
			this->elapsedTime -= this->nextGenerationTime;
			glm::vec3 randSpeed = glm::vec3(grandf(-0.10f, 0.20f), grandf(-0.10f, 0.20f), grandf(-0.10f, 0.20f));
			glUniform3f(glGetUniformLocation(programID, "vRandomSeed"), randSpeed.x, randSpeed.y, randSpeed.z);
		}
 
		glEnable(GL_RASTERIZER_DISCARD);
		glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, this->transformFeedbackBuffer);
 
		glBindVertexArray(this->VAO[this->currentBuffer]);
		glEnableVertexAttribArray(1);
 
		glBindBufferBase(GL_TRANSFORM_FEEDBACK_BUFFER, 0, this->particleBuffer[1-this->currentBuffer]);
 
		glBeginQuery(GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, this->query);
		glBeginTransformFeedback(GL_POINTS);
 
		if (this->first)
		{
			glDrawArrays(GL_POINTS, 0, this->nbParticles);
			this->first = false;
		}
		else
			glDrawTransformFeedback(GL_POINTS, this->transformFeedbackBuffer);
 
		glEndTransformFeedback();
 
		glEndQuery(GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN);
		glGetQueryObjectiv(this->query, GL_QUERY_RESULT, &this->nbParticles);
 
		std::cout<<this->nbParticles<<std::endl;
 
		this->currentBuffer = 1 - this->currentBuffer;
 
		glBindTransformFeedback(GL_TRANSFORM_FEEDBACK, 0);
	glUseProgram(0);
}
 
void ParticleSystemTransformFeedback::setGeneratorProperty(glm::vec3 genPosition, glm::vec3 genVelocityMin, glm::vec3 genVelocityMax, glm::vec3 genGravityVector, glm::vec3 genColor, 
							float genLifeMin, float genLifeMax, float genSize, float every, int numToGenerate)
{
	this->genPosition = genPosition;
	this->genVelocityMin = genVelocityMin;
	this->genVelocityRange = genVelocityMax - genVelocityMin;
	this->genGravity = genGravity;
	this->genColor = genColor;
	this->genSize = genSize;
	this->genLifeMin = genLifeMin;
	this->genLifeRange = genLifeMax - genLifeMin;
	this->nextGenerationTime = every;
	this->elapsedTime = 0.8f;
	this->nbToGenerate = numToGenerate;
}
 
void ParticleSystemTransformFeedback::clearAllParticles()
{
 
}
 
bool ParticleSystemTransformFeedback::releaseParticleSystem()
{
	return true;
}
 
void ParticleSystemTransformFeedback::apply(float time, glm::vec3* position, glm::mat3* rotation, glm::vec3* scale, GlobalInformation* globalInformation)
{
	this->updateParticles(time - previousTime);
	this->previousTime = time;
	glm::vec3 view = globalInformation->getCurrentCamera()->getFocus() - globalInformation->getCurrentCamera()->getPostion();
	view = glm::normalize(view);
 
	this->quad1 = glm::cross(view, globalInformation->getCurrentCamera()->getUpVector());
	this->quad1 = glm::normalize(this->quad1);
 
	this->quad2 = glm::cross(view, this->quad1);
	this->quad2 = glm::normalize(this->quad2);
 
	renderParticles(globalInformation);
}
 
int ParticleSystemTransformFeedback::getNbParticles()
{
	return this->nbParticles;
}
 
ParticleSystemTransformFeedback::~ParticleSystemTransformFeedback()
{
 
}

Update Shader :

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#version 330 
 
layout (location = 0) in vec3 vPosition; 
layout (location = 1) in vec3 vVelocity; 
layout (location = 2) in vec3 vColor; 
layout (location = 3) in float fLifeTime; 
layout (location = 4) in float fSize; 
layout (location = 5) in int iType; 
 
out vec3 vPositionPass; 
out vec3 vVelocityPass; 
out vec3 vColorPass; 
out float fLifeTimePass; 
out float fSizePass; 
out int iTypePass; 
 
void main() 
{ 
  vPositionPass = vPosition; 
  vVelocityPass = vVelocity; 
  vColorPass = vColor; 
  fLifeTimePass = fLifeTime; 
  fSizePass = fSize; 
  iTypePass = iType; 
}

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#version 330 
 
layout(points) in; 
layout(points) out; 
layout(max_vertices = 40) out; 
 
// All that we get from vertex shader
 
in vec3 vPositionPass[]; 
in vec3 vVelocityPass[]; 
in vec3 vColorPass[]; 
in float fLifeTimePass[]; 
in float fSizePass[]; 
in int iTypePass[]; 
 
// All that we send further
 
out vec3 vPositionOut; 
out vec3 vVelocityOut; 
out vec3 vColorOut; 
out float fLifeTimeOut; 
out float fSizeOut; 
out int iTypeOut; 
 
uniform vec3 vGenPosition; // Position where new particles are spawned
uniform vec3 vGenGravityVector; // Gravity vector for particles - updates velocity of particles 
uniform vec3 vGenVelocityMin; // Velocity of new particle - from min to (min+range)
uniform vec3 vGenVelocityRange; 
 
uniform vec3 vGenColor; 
uniform float fGenSize;  
 
uniform float fGenLifeMin, fGenLifeRange; // Life of new particle - from min to (min+range)
uniform float fTimePassed; // Time passed since last frame
 
uniform vec3 vRandomSeed; // Seed number for our random number function
vec3 vLocalSeed; 
 
uniform int iNumToGenerate; // How many particles will be generated next time, if greater than zero, particles are generated
 
// This function returns random number from zero to one
float randZeroOne() 
{ 
    uint n = floatBitsToUint(vLocalSeed.y * 214013.0 + vLocalSeed.x * 2531011.0 + vLocalSeed.z * 141251.0); 
    n = n * (n * n * 15731u + 789221u); 
    n = (n >> 9u) | 0x3F800000u; 
 
    float fRes =  2.0 - uintBitsToFloat(n); 
    vLocalSeed = vec3(vLocalSeed.x + 147158.0 * fRes, vLocalSeed.y*fRes  + 415161.0 * fRes, vLocalSeed.z + 324154.0*fRes); 
    return fRes; 
} 
 
void main() 
{ 
  vLocalSeed = vRandomSeed; 
 
  // gl_Position doesn't matter now, as rendering is discarded, so I don't set it at all
 
  vPositionOut = vPositionPass[0] + vec3(0.0, 0.01, 0.0); 
  vVelocityOut = vVelocityPass[0]; 
  if(iTypePass[0] != 0)vPositionOut += /*vVelocityOut*fTimePassed + */vec3(0.0, 0.05, 0.0); 
  if(iTypePass[0] != 0)vVelocityOut += vGenGravityVector*fTimePassed; 
 
  vColorOut = vColorPass[0]; 
  fLifeTimeOut = fLifeTimePass[0]-fTimePassed; 
  fSizeOut = fSizePass[0]; 
  iTypeOut = iTypePass[0]; 
 
  if(iTypeOut == 0) 
  { 
    EmitVertex(); 
    EndPrimitive();
 
    for(int i = 0; i < iNumToGenerate; i++) 
    { 
      vPositionOut = vec3(0.0, -1.0, 0.0);
      vVelocityOut = vGenVelocityMin+vec3(vGenVelocityRange.x*randZeroOne(), vGenVelocityRange.y*randZeroOne(), vGenVelocityRange.z*randZeroOne()); 
	  vVelocityOut = vec3(0.0, 0.1, 0.0);
      vColorOut = vGenColor; 
      fLifeTimeOut = fGenLifeMin+fGenLifeRange*randZeroOne(); 
      fSizeOut = fGenSize; 
      iTypeOut = 1; 
      EmitVertex(); 
      EndPrimitive(); 
    } 
  } 
  else /*if(fLifeTimeOut > 0.0) */
  { 
      EmitVertex(); 
      EndPrimitive();  
  } 
}

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#version 330
 
out vec4 vColor;
 
void main()
{
	vColor = vec4(1.0, 1.0, 1.0, 1.0);
}

Render Shader :

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#version 330
 
layout (location = 0) in vec3 vPosition;
layout (location = 2) in vec3 vColor;
layout (location = 3) in float fLifeTime;
layout (location = 4) in float fSize;
layout (location = 5) in int iType;
 
out vec3 vColorPass;
out float fLifeTimePass;
out float fSizePass;
out int iTypePass;
 
 
uniform struct Matrices
{
	mat4 mProj;
	mat4 mView;
} matrices;
 
void main()
{
   gl_Position = vec4(vPosition, 1.0);
   vColorPass = vColor;
   fSizePass = fSize;
   fLifeTimePass = fLifeTime;
   iTypePass = iType;
}

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#version 330
 
uniform struct Matrices
{
	mat4 mProj;
	mat4 mView;
} matrices;
 
uniform vec3 vQuad1, vQuad2;
 
layout(points) in;
layout(triangle_strip) out;
layout(max_vertices = 4) out;
 
in vec3 vColorPass[];
in float fLifeTimePass[];
in float fSizePass[];
in int iTypePass[];
 
smooth out vec2 vTexCoord;
flat out vec4 vColorPart;
 
void main()
{
  if(iTypePass[0] == 0)
  {
    vec3 vPosOld = gl_in[0].gl_Position.xyz;
    float fSize = fSizePass[0];
    mat4 mVP = matrices.mProj*matrices.mView;
 
    vColorPart = vec4(vColorPass[0], fLifeTimePass[0]);
 
	vec3 vPos = vPosOld;
    vTexCoord = vec2(0.0, 0.0);
    gl_Position = mVP*vec4(vPos, 1.0);
    EmitVertex();
 
    vPos = vPosOld + vec3(0.0, 0.0, 0.1);
    vTexCoord = vec2(0.0, 1.0);
    gl_Position = mVP*vec4(vPos, 1.0);
    EmitVertex();
 
    vPos = vPosOld + vec3(0.0, 0.1, 0.0);
    vTexCoord = vec2(1.0, 0.0);
    gl_Position = mVP*vec4(vPos, 1.0);
    EmitVertex();
 
    vPos = vPosOld + vec3(0.0, 0.1, 0.1);
    vTexCoord = vec2(1.0, 1.0);
    gl_Position = mVP*vec4(vPos, 1.0);
    EmitVertex();
 
    EndPrimitive();
  }
}

Code :

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#version 330
 
uniform sampler2D gSampler;
 
smooth in vec2 vTexCoord;
flat in vec4 vColorPart;
 
out vec4 FragColor;
 
void main()
{
	FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}

Merci d'avance pour votre aide,
Robin

[robinsondesbois]

En fait c'est de ma faute.
Dans mon geometry shader de rendu je dessine que les particules génératrices

J'ai donc compris le tuto et ça fonctionne maintenant