Direct Shader Sampling in Painterly Rendering for Animation

We present a technique for generating stroke parameters in particlebased painterly rendering algorithms that guarantees temporal coherence in animation through directly sampling shaders. To determine the appropriate color for a brush stroke, techniques like [Meier 1996] render the scene into reference pictures using traditional techniques. This reference picture is then queried by applying the camera transform to the particle’s position. This transform will not always map to the correct pixel which can lead to noticeable temporal discontinuities when there is a significant color difference between two neighboring pixels. When a stroke particle lies on the edge of an object, the brush stroke will sometimes flicker between the two neighboring colors. Previously, as described in [Meier 1996], scenes would be broken up into different layers, and image processing effects were applied to reference pictures to ensure that the right color is sampled. Our method requires no post processing effects to ensure temporal coherence around these edge cases.