GlGenVertexArrays has no effect in Qt5.0.2?

stereomatching

platform : mac osx 10.8.3
compiler : clang3.2

Are these kind of codes do not work on Qt5.0.2?

@
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
@

example :

This function has no effect in Qt5, VAO do not record the attributes at all
It will overwrite the first object in the buffer
@
void ch5OverlapNoDepth::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT);

glBindVertexArray(vaoObject1_);
glDrawElements(GL_TRIANGLES, indexData_.size(), GL_UNSIGNED_INT, 0);

glBindVertexArray(vaoObject2_);
glDrawElements(GL_TRIANGLES, indexData_.size(), GL_UNSIGNED_INT, 0);

glBindVertexArray(0);

}
@

If I want to let QGLWidget draw more than one object
I have to bind the buffer and enable the attribute in the function
@
void ch5OverlapNoDepth::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT);

glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject_[0]);

size_t colorDataOffset = sizeof(GLfloat) * 4 * numberOfVertices;
int vertexLocation = program_.attributeLocation("position");
int colorLocation = program_.attributeLocation("color");    

program_.enableAttributeArray(vertexLocation);
program_.enableAttributeArray(colorLocation);

glVertexAttribPointer(vertexLocation, 4, GL_FLOAT, GL_FALSE, 0, 0);
glVertexAttribPointer(colorLocation, 4, GL_FLOAT, GL_FALSE, 0, (GLvoid const*)colorDataOffset);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, positionBufferObject_[1]);
glDrawElements(GL_TRIANGLES, indexData_.size(), GL_UNSIGNED_INT, 0);   

size_t posDataOffset = sizeof(float) * 4 * (numberOfVertices / 2);
colorDataOffset += sizeof(float) * 4 * (numberOfVertices / 2);

//Use the same buffer object previously bound to GL_ARRAY_BUFFER.
program_.enableAttributeArray(vertexLocation);
program_.enableAttributeArray(colorLocation);
glVertexAttribPointer(vertexLocation, 4, GL_FLOAT, GL_FALSE, 0, (void*)posDataOffset);
glVertexAttribPointer(colorLocation, 4, GL_FLOAT, GL_FALSE, 0, (void*)colorDataOffset);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, positionBufferObject_[1]);
glDrawElements(GL_TRIANGLES, indexData_.size(), GL_UNSIGNED_INT, 0);

}
@

This paintGL looks more expensive than the original paintGL which simply call the associate VAO
How could I make use of VAO in Qt5.0.2?Thanks

hesheit

I now face with this problem like you. T_T

hesheit

I can fix it.

You need to make sure your opengl version is 3.0 or newer.
glGenVertexArray is available in these versions and then use
create(), bind() , etc instead.

ZapB

Or use the QOpenGL_APPLE_vertex_array_object extension class if using OpenGL 2.1.