Problem with Particle and OpenGL, nothing is drawn - c++

Question

I'm learning OpenGL and I'm trying to implement some particles in my application.
To do so, I followed some courses.
But when I try to render my particles, nothing happen, it doesn't even enter the shader (I tried to put some infinite loop in it and nothing happened). I tried a lot of thing, maybe there is something I did not understand..
I created a class Particle, with a constructor, an update and a draw method, I followed every step of the course, and adapted it to my class (the course is doing everything in the main loop).
My particles class got some private members:
private:
size_t maxSize_;
std::vector<float> quadData_;
unsigned int dataVbo_;
std::vector<float> posData_;
unsigned int posVbo_;
std::vector<float> colorData_;
unsigned int colorVbo_;
std::list<Particle> allParticles_;
and here is the initialization of Particles:
Particles::Particles(size_t maxSize)
: maxSize_(maxSize), quadData_({-0.5f, -0.5f, 0.0f, 0.5f, -0.5f, 0.0f, -0.5f, 0.5f, 0.0f, 0.5f, 0.5f, 0.0f})
{
posData_.resize(maxSize_*4);
colorData_.resize(maxSize_*4);
glGenBuffers(1, &dataVbo_);
glBindBuffer(GL_ARRAY_BUFFER, dataVbo_);
glBufferData(GL_ARRAY_BUFFER, quadData_.size() * sizeof(float), quadData_.data(), GL_STATIC_DRAW);
// The VBO containing the positions and sizes of the particles
glGenBuffers(1, &posVbo_);
glBindBuffer(GL_ARRAY_BUFFER, posVbo_);
// Initialize with empty (NULL) buffer : it will be updated later, each frame.
glBufferData(GL_ARRAY_BUFFER, maxSize_ * 4 * sizeof(float), NULL, GL_STREAM_DRAW);
// The VBO containing the colors of the particles
glGenBuffers(1, &colorVbo_);
glBindBuffer(GL_ARRAY_BUFFER, colorVbo_);
// Initialize with empty (NULL) buffer : it will be updated later, each frame.
glBufferData(GL_ARRAY_BUFFER, maxSize_ * 4 * sizeof(float), NULL, GL_STREAM_DRAW);
}
and the draw:
void Particles::draw(){
size_t count(posData_.size());
glBindBuffer(GL_ARRAY_BUFFER, posVbo_);
glBufferData(GL_ARRAY_BUFFER, maxSize_ * 4 * sizeof(float), NULL, GL_STREAM_DRAW); // Buffer orphaning, a common way to improve streaming perf. See above link for details.
glBufferSubData(GL_ARRAY_BUFFER, 0, count * sizeof(float), posData_.data());
glBindBuffer(GL_ARRAY_BUFFER, colorVbo_);
glBufferData(GL_ARRAY_BUFFER, maxSize_ * 4 * sizeof(float), NULL, GL_STREAM_DRAW); // Buffer orphaning, a common way to improve streaming perf. See above link for details.
glBufferSubData(GL_ARRAY_BUFFER, 0, count * sizeof(float) * 4, colorData_.data());
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, dataVbo_);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
// 2nd attribute buffer : positions of particles' centers
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, posVbo_);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*) 0);
// 3rd attribute buffer : particles' colors
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, colorVbo_);
glVertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, 0, (void*) 0);
glVertexAttribDivisor(0, 0); // particles vertices : always reuse the same 4 vertices -> 0
glVertexAttribDivisor(1, 1); // positions : one per quad (its center) -> 1
glVertexAttribDivisor(2, 1); // color : one per quad -> 1
glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, count);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
}
And in my main loop I'm doing this:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
myParticules.update(elapsedTime);
glDisable(GL_DEPTH_TEST);
glUseProgram(_particleShad);
myParticles.draw();
I'm also sending some uniform vec and mat, but nothing important.
In my shader I only try to do this:
Vertex :
gl_Position = vec4(squareVertices.xyz, 1);
//squareVertices contain the vertices of my square for my particles
Fragment :
color = vec4(1, 1, 1, 1);
I don't find anything wrong, I really need some help, I'm totally lost.

Answer 1

You must create a VAO (Vertex Array Object):
class Particles {
private:
// add:
GLuint vao;
...
Initialization:
Particles::Particles(size_t maxSize)
: maxSize_(maxSize), quadData_({-0.5f, -0.5f, 0.0f, 0.5f, -0.5f, 0.0f, -0.5f, 0.5f, 0.0f, 0.5f, 0.5f, 0.0f})
{
posData_.resize(maxSize_*4);
colorData_.resize(maxSize_*4);
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glGenBuffers(1, &dataVbo_);
glBindBuffer(GL_ARRAY_BUFFER, dataVbo_);
glBufferData(GL_ARRAY_BUFFER, quadData_.size() * sizeof(float), quadData_.data(), GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*) 0);
// The VBO containing the positions and sizes of the particles
glGenBuffers(1, &posVbo_);
glBindBuffer(GL_ARRAY_BUFFER, posVbo_);
// Initialize with empty (NULL) buffer : it will be updated later, each frame.
glBufferData(GL_ARRAY_BUFFER, maxSize_ * 4 * sizeof(float), NULL, GL_STREAM_DRAW);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*) 0);
// The VBO containing the colors of the particles
glGenBuffers(1, &colorVbo_);
glBindBuffer(GL_ARRAY_BUFFER, colorVbo_);
// Initialize with empty (NULL) buffer : it will be updated later, each frame.
glBufferData(GL_ARRAY_BUFFER, maxSize_ * 4 * sizeof(float), NULL, GL_STREAM_DRAW);
glEnableVertexAttribArray(2);
glVertexAttribPointer(2, 4, GL_FLOAT, GL_FALSE, 0, (void*) 0);
glVertexAttribDivisor(0, 0); // particles vertices : always reuse the same 4 vertices -> 0
glVertexAttribDivisor(1, 1); // positions : one per quad (its center) -> 1
glVertexAttribDivisor(2, 1); // color : one per quad -> 1
}
Drawing code:
void Particles::draw(){
size_t count(posData_.size());
glBindBuffer(GL_ARRAY_BUFFER, posVbo_);
glBufferSubData(GL_ARRAY_BUFFER, 0, count * sizeof(float), posData_.data());
glBindBuffer(GL_ARRAY_BUFFER, colorVbo_);
glBufferSubData(GL_ARRAY_BUFFER, 0, count * sizeof(float) * 4, colorData_.data());
glBindVertexArray(vao);
glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, count);
}
Notice how you don't need to update your VAO state during the draw() call, only during the initialization.