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Qt + OpenGL 3+  Frustum not completely rendered

Hi everyone!
I'm currently stuck with an issue when trying to draw a simple geometry in a QGLWidget. Indeed the frustum is not completely rendered.
Actually I've set a perspective of 45°, my camera is translated to 4 units towards the negative Z axis and all my geometry is drawn on the z=0 plane. Thus, any point on this plane situated within a square from (2, 2 (0)) to (2, 2, (0)) must be rendered as shown on my schematic:
!http://imageshack.com/a/img843/8357/1n1t.png(Schem)!
But actually my frustum is not totally rendered. Indeed i've created a simple trapezoidal geometry which is totally inside my frustum, but when rendering the geometry is incomplete as shown in the next screenshot:
!http://imageshack.com/a/img845/9657/sdpt.png(sc)!
So I'm wondering if I've missed a point since I'm not able to render all the content of my frustum.
I've set my MVP matrix as:
@void GLWidget::resizeGL(int w, int h)
{
// Set OpenGL viewport to cover whole widget
glViewport(0, 0, w, h);// Calculate aspect ratio qreal aspect = qreal(w) / qreal(h); //qreal(h ? h : 1); // Set near plane to 3.0, far plane to 7.0, field of view 45 degrees const qreal zNear = 2.0, zFar = 7.0; qreal fov = 45.0; // Reset projection m_oProjection.setToIdentity(); // Set perspective projection m_oProjection.perspective(fov, aspect, zNear, zFar);
}@
then in my paintGL() function I calculate the projection matrix as:
@
// Calculate model view transformation
QMatrix4x4 matrix;
matrix.translate(0.0, 0.0, 4.0f);// Set modelviewprojection matrix m_oProgram.setUniformValue("mvp_matrix", m_oProjection * matrix);@
And finally my geometry is set as:
@
// Initializing Vertices attributes: position and color
VertexData vertices[numVertices] = {
{QVector3D(2, 1, 0), QVector2D(0, 1)}, //v0  top left
{QVector3D(1, 1, 0), QVector2D(0, 0)}, //v1  bottom left
{QVector3D(1, 1, 0), QVector2D(1, 0)}, //v2  bottom right
{QVector3D(2, 1, 0), QVector2D(1, 1)} //v3  top right
};@Does anyone have ever encounter such an issue? Do you think I missed a parameter to set in my pipeline?
Yhanks in advance for your answers!!