Rendering on a budget: a framework for time-critical rendering

We present a technique for optimizing the rendering of high-depth complexity scenes. Prioritized-Layered Projection (PLP) does this by rendering an estimation of the visible set. The novelty in our work lies in the fact that we do not explicitly compute visible sets. Instead, our work is based on computing on demand a priority order for the polygons that maximizes the likelihood of rendering visible polygons before occluded ones for any given scene. Given a fixed budget, e.g. time or number of triangles, our rendering algorithm makes sure to render geometry, respecting the computed priority. There are two main steps to our technique: (1) an occupancy based tessellation of space; and (2) a solidity based traversal algorithm. PLP works by computing an occupancy based tessellation of space, which tends to have smaller cells where there are more geometric primitives, e.g., polygons. In this spatial tessellation, each cell is assigned a solidity value, which is directly proportional to its likelihood of occluding other cells. In its simplest form, a cell's solidity value is directly proportional to the number of polygons contained within it. During our traversal algorithm, cells are marked for projection, and the geometric primitives contained within them actually rendered. The traversal algorithm makes use of the cells' solidity, and other view-dependent information to determine the ordering in which to project cells. By tailoring the traversal algorithm to the occupancy based tessellation, we can achieve very good frame rates with low preprocessing and rendering costs. We describe our technique and its implementation in detail. We also provide experimental evidence of its performance and briefly discuss extensions of our algorithm.