US Patent 11936840 Perspective based green screening

A method of generating a composite image includes capturing a video image of a physical scene with a camera, identifying a green-screen region within the video image, identifying a viewpoint and a position and/or orientation of the green-screen region relative to the viewpoint, and generating a modified video image rendered from the viewpoint onto a display surface in which the green-screen region is replaced with an image of a virtual object. The image of the virtual object is generated by projection rendering of a model of the virtual object based on the position and/or orientation of the green-screen region relative to the viewpoint such that the virtual object is constrained within the green-screen region.