QGLWidget offscreen rendering and GL_MAX_TEXTURE_SIZE

[JulienMaille]

Dear Qt-ers,
I wrote a small application displaying an heightmap with a texture and I would like to export a snapshot bigger than my screen.
I found the convenient QGLWidget::renderPixmap() but unfortunately it renders the scene with a "virtual" OpenGL1.1 device that has a limit of 1024x1024 for the texture size (GL_MAX_TEXTURE_SIZE).
As expected, it works fine for small texture, but above the 1024² limit, the heightmap is not textured.

Do I have alternative to achieve my "high-res" capture of the scene?

Thanks a lot