Z-Thickness Blending: Effective Fragment Merging for Multi-Fragment Rendering

Abstract

An effective fragment merging technique is presented in this study that addresses multi-fragment problems, including fragment overflow and z-fighting, and provides visual effects that are beneficial for various screen-space rendering algorithms. The proposed method merges locally adjacent fragments along the viewing direction to resolve the aforementioned problems based on cost-effective multi-layer representation and coplanar blending. We introduce a z-thickness model based on the radiosity spreading from the viewing z-direction. Moreover, we present the fragment-merging schemes and rules for determining the visibility of the merged fragments based on the proposed z-thickness model. The proposed method is targeted at multi-fragment rendering that handles individual fragments (e.g., k-buffer) instead of representing the fragments as an approximated transmittance function. In addition, our method provides a smooth visibility transition across overlapping fragments, resulting in visual advantages in various visualization applications. In this paper, we demonstrate the advantages of the proposed method through several screen-space rendering applications.