Evaluating PQPM for Usage in Combination with Continuous LOD in VR

Sammanfattning: The use of Virtual Reality (VR) is growing in commercial use, one type of VR headset, called mobile stand-alone system has limited resources for computing and memory. Because of this, when developing real-time applications for this type of VR headset, performance needs to be heavily considered. One popular optimization technique is Level-of-Detail (LOD) which is a technique that represents a model at various resolutions. One type of LOD is called continuous LOD which can represent a model at a continuous spectrum of detail, this is not frequently used, however, because of being less intuitive and more difficult to implement than other versions. This project researched a type of continuous LOD used with a new metric called Pixel Quality Per Meter (PQPM). PQPM relies on having a minimum edge length calculated using a model's screen coverage in relation to its size. To answer whether PQPM can be used together with continuous LOD for intuitive, simple, and efficient updating and rendering in VR. The continuous LOD only uses one low-poly mesh which is tessellated with the help of a Vertex Displacement Map (VDM) to the desired quality. This approach is then evaluated using Nvidia FLIP, an image comparison application that emulates the human visual system. The result was an intuitive and easily implementable LOD which is used together with PQPM to decide the optimal quality given the models size and coverage on the screen. The usage of PQPM did not result in optimal quality at all distances, due to smaller segments being present, which could disappear completely at far distances. The continuous LOD combined with the PQPM did also not scale well but worked well at lower qualities. The study showed groundwork for how PQPM could work together with continuous LOD, it provides a more intuitive and easily implementable continuous LOD than previous approaches, however, because of the scalability issues, further work needs to be done to optimize this approach.