Disclosed embodiments pertain to apparatus, systems, and methods for mixed reality. In some embodiments, a camera pose relative to a tracked object in a live image may be determined and used to render synthetic images from keyframes in a 3D model without the tracked object. Optical flow magnitudes for pixels in a first mask region relative to a subset of the synthetic images may be determined and the optical flow magnitudes may be used to determine pixels in each of the subset of synthetic images that correspond to pixels in the first mask. For each pixel in the first mask, a corresponding replacement pixel may be determined as a function of pixels in the subset of synthetic images that correspond to the corresponding pixel in the first mask.