Addressing intersection artifacts on textured, geometrically rendered vector data in 3D applications
Sammanfattning: There exist various methods to render vector data in 3D applications. One such method is to render the data geometrically, where polyline data is tessellated into some geometry that is rendered on top of the 3D terrain. Having explicit access to the line geometry is valuable to applications that demand high visual quality, as it enables applying various effects to the line data. However, a prominent visual artifact in geometrically rendered line data occurs around intersections, where it is hard to render lines seamlessly. In this thesis paper I present a method that is aimed to address this issue. By generating explicit geometry for line intersections, and by enforcing several restrictions on the design of the applied textures, the proposed method ensures seamless rendering of textures over complex intersections, including intersections that adjoin lines with different textures assigned to them. To ensure minimal performance overhead at runtime the proposed method computes all the required geometry offline, and stores it in a static vertex buffer on the GPU. At runtime a separate index buffer is generated, which is used to reference the vertices required to generate the appropriate geometry. Finally, the proposed method supports interactively assigning textures to line data at runtime, which could for example enable filtering and focusing of vector data. Empirical measurements are provided for runtime performance, these measurements show that the performance overhead introduced by the method is reasonably small, making the proposed method a feasible addition to interactive systems. A qualitative comparison is used to validate the visual results, where examples show successful rendering of several intersections that include a variety of textures. The proposed method paves the way for possible future work, for example in defining a taxonomy of textures, along with a set of rules describing how each group of textures should be drawn at intersections.
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