How to use QOpenGLBuffer to render data?

[themts]

Hey guys,

I'm porting some code to QT and I could need some help.
I want to create a VBO and render it as a linestrip.
In plain opengl I would:

1. glGenBuffers
2. glBindBuffer
3. glEnableClientState(GL_VERTEX_ARRAY)
4. glBufferData to create a buffer
5. fill data
6. glInterleavedArrays
7. glDrawArrays

Now to QT:

1. I created a QOpenGLBuffer:
   m_vertexBuffer = new QOpenGLBuffer(QOpenGLBuffer::VertexBuffer);
   m_vertexBuffer->create()
   m_vertexBuffer->setUsagePattern(QOpenGLBuffer::DynamicDraw);
   m_vertexBuffer->bind();
   m_vertexBuffer->allocate(20 * sizeof(QVector2D)); //Lets use 20 fixed vertex here

2. Fill buffer with some test-data
   for (int i = 0; i < 20; i++) {
   QVector2D vec;
   vec.setX(i);
   vec.setY(sin(i));
   m_vertexBuffer->write(i * sizeof(QVector2D), &vec, sizeof(QVector2D));
   }

3. Now I need to display the data. How?

CU
mts

[A Former User]

Hi!

Are you using QWidgets or QtQuick? You wrote you would use glDrawArrays in plain opengl. Why don't you want to use it here?

[themts]

I'm using QtQuick.
I tried using glDrawArrays, but I don't see anything

void NTestFboRenderer::render()
{
m_vertexBuffer->bind();
for (int i = 0; i < 20; i++) {
QVector2D vec;
vec.setX(i);
vec.setY(sin(i));
m_vertexBuffer->write(i * sizeof(QVector2D), &vec, sizeof(QVector2D));
}

glColor4f(1, 0, 0, 1);
glDrawArrays(GL_LINE_STRIP, 0, 20);
m_vertexBuffer->release();

}

How do I tell opengl how to interpret my vertexbuffer?
I thought I can do it by glInterleavedArrays but can I interpret a QVector2D as GL_V2F ?

[A Former User]

I'm not an expert in the field. Maybe this example code can help you: https://qt.gitorious.org/qt/qtdeclarative/source/15e58df3386b5438f6ae114a51ad4a258085e70b:examples/quick/scenegraph/shared/logorenderer.cpp
The whole example can be found here: http://doc.qt.io/qt-5/qtquick-scenegraph-textureinthread-example.html