This disclosure describes techniques for modifying application program interface (API) calls in a manner that can cause a device to render native three dimensional (3D) graphics content in stereoscopic 3D. The techniques of this disclosure can be implemented in a manner where API calls themselves are modified, but the API itself and the GPU hardware are not modified. The techniques of the present disclosure include using the same viewing frustum defined by the original content to generate a left-eye image and a right-eye image and shifting the viewport offset of the left-eye image and the right-eye image.