US Patent 9142056 Mixed-order compositing for images having three-dimensional painting effects

Rendering 3D paintings can be done by compositing brush strokes embedded in space. Image elements are rendered into an image representable by a pixel array wherein at least some of the image elements correspond to simulated painting strokes. A method may include determining stroke positions in a 3D space, determining stroke orders, and for each pixel to be addressed, determining a pixel color value by determining strokes intersections with a view ray for that pixel, determining a depth order and a stroke order for intersecting fragments, each fragment having a color, alpha value, depth, and stroke order, assigning an intermediate color to each of the fragments, corresponding to a compositing of nearby fragments in stroke order, and assigning a color to the pixel that corresponds to a compositing of the fragments using the intermediate colors assigned to the fragments. The compositing may be done in depth order.