OpenGL buffer update [duplicate] - c++

Question

This question already has answers here:
What is the proper way to modify OpenGL vertex buffer?
(3 answers)
Closed 2 years ago.
Currently I'm writing a program that simulates water. Here are the steps that I do:
Create water surface - plane.
Create VAO
Create vertex buffer object in which I store normals and vertices.
Bind pointers to this VBO.
Create index buffer object.
Then I render this plane using glDrawElements and then I invoke an update() function which changes positions of vertices of water surface. After that I invoke glBufferSubData function to update vertices positions.
When I do that - nothing happens as if the buffer isn't changed.
Here's the code snippet:
glGenBuffers(1, &vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Oscillator) * nOscillators, oscillators, GL_DYNAMIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Oscillator), 0);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Oscillator), (const GLvoid*)12);
glEnableVertexAttribArray(0); // Vertex position
glEnableVertexAttribArray(2); // normals position
glGenBuffers(1, &indicesBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indicesBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(unsigned int) * nIndices, indices, GL_DYNAMIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indicesBuffer);
glBindVertexArray(0);
Then render:
glBindVertexArray(vaoHandle);
glDrawElements(GL_TRIANGLES, nIndices, GL_UNSIGNED_INT, 0);
update(time);
And update function:
//some calculations
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Oscillator) * nOscillators, oscillators);
Oscillator - it's a structure that has: 8 floats respectively - x, y, z (vertex position), nx, ny, nz (normals), upSpeed, newY
oscillators - this is an array of Oscillator structures.
What I do wrong?

Answer 1

Before updating the data you have to bind the correct buffer. E.g:
glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
Since you are updating the full buffer at once I would suggest to use glMapBuffer to update it
void* data = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
//[...] update the buffer with new values
bool done = glUnmapBuffer(GL_ARRAY_BUFFER);
And remember to wait (or force) a glFlush() before modifying the data you are goin to copy to the gl buffer.