OpenGL rendering problem

[spud]

I have a project where I render a recorded gps path on an aereal photo. I do this using a QGraphicsScene with a QGraphicsPathItem on a QGraphicsPixmapItem. Simple enough. When I use OpenGL to render the scene, i.e.

QGraphicsView::setViewport(new QGLWidget(QGLFormat(QGL::SampleBuffers)));

QGraphicsView::setViewport(new QGLWidget(QGLFormat(QGL::SampleBuffers)));

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i notice that the path loses accuracy, as if it is restricted by a lower resolution. See the attached snapshots. Does anybody have an idea why this is, or how i can fix it?