rendering - Why do I see spaces between polygons in OpenGL, only on an Nvidia 720M?

I'm developing an OpenGL application that renders .obj 3D models. I use VBOs to render the polygons. Using the same code, the loaded models appear fine on all PCs, except on my Nvidia 720M.

My laptop sports an Intel HD 4000 embedded graphics GPU, and an Nvidia 720M. When I use the Intel GPU, it looks fine, but when I load it on the Nvidia 720M, spaces appear around polygons like so:

On Nvidia 720M GPU:

On everything else:

No other 3D application that runs on the Nvidia 720M GPU has the same issue. I am using the latest drivers.

Is this a problem with my application? How can I fix it?

Answer

Just a hunch... is your GPU somehow doing polygon antialiasing? That would cause such artifacts. For example, if two neighbouring polygons each cover a particular pixel for 50%, the total coverage (alpha) for that pixel would be 75%, not 100%.

Try forcing the option off:

glDisable(GL_POLYGON_SMOOTH);

Or even:

glHint(GL_POLYGON_SMOOTH_HINT, GL_FASTEST);