A performance comparison between quadtree and tessellation LOD solutions for planetary terrain

Sammanfattning: Background. Rendering planets with high detail from orbit to surface level is becoming increasingly common in video games. In this thesis, two solutions to achieving this will be compared, a quadtree solution and a tessellation solution. These solutions both implement an adaptive level of detail on a spherical shape. The quadtree solution uses six quadtrees to construct the planetary terrain mesh on the CPU with higher detail closer to the viewer. The tessellation solution uses the GPU to subdivide areas of a basic low-resolution model to achieve higher levels of detail close to the viewer. Objectives. Related work that has implemented these solutions uses old hardware and there is a lack of performance data on these solutions running on modern hardware. The objective of this project is to provide performance data and a comparison between the quadtree solution and the tessellation solution on modern hardware. This comparison will include a discussion of the negative and positive performance aspects of the two solutions. Methods. The two solutions will be implemented to create two similar-looking applications with a focus on only the technical aspects of rendering a globe mesh with each of these solutions. The frame time both on the CPU and on the GPU will be measured for each solution. The measurements will be taken at four different distances from the globe, meaning four different levels of detail. Due to a limitation of tessellation, this solution has to be provided with a higher resolution base model to achieve similar detail levels at the surface level. Results. The results show the quadtree frame time increasing with measurements taken closer to the surface of the globe. The tessellation results show a larger performance impact, though this is due to the base globe mesh being swapped for a higher-resolution model. Conclusions. The result suggests that the tessellation solution performs worse, however, the tessellation solution still shows little to no performance loss when comparing frame time measured on the same base mesh, even though the detail difference between them is high. The quadtree solution has an overall better performance and provides more control over the detail levels. The lack of control over the detail levels in the tessellation solution means that the detail level can not be matched exactly, which leads to the tessellation solution giving a richer topology.