This post proposes a taxonomy for classifying rendering engines based on two key dimensions: the scene representation (explicit vs. implicit) and the rendering technique (rasterization vs. ray tracing). Explicit representations, like triangle meshes, directly define the scene geometry, while implicit representations, like signed distance fields, define the scene mathematically. Rasterization projects scene primitives onto the screen, while ray tracing simulates light paths to determine pixel colors. The taxonomy creates four categories: explicit/rasterization (traditional real-time graphics), explicit/ray tracing (becoming increasingly common), implicit/rasterization (used for specific effects and visualizations), and implicit/ray tracing (offering unique capabilities but computationally expensive). The author argues this framework provides a clearer understanding of rendering engine design choices and future development trends.
FastDoom achieves its speed primarily through optimizing data access patterns. The original Doom wastes cycles retrieving small pieces of data scattered throughout memory. FastDoom restructures data, grouping related elements together (like vertices for a single wall) for contiguous access. This significantly reduces cache misses, allowing the CPU to fetch the necessary information much faster. Further optimizations include precalculating commonly used values, eliminating redundant calculations, and streamlining inner loops, ultimately leading to a dramatic performance boost even on modern hardware.
The Hacker News comments discuss various technical aspects contributing to FastDoom's speed. Several users point to the simplicity of the original Doom rendering engine and its reliance on fixed-point arithmetic as key factors. Some highlight the minimal processing demands placed on the original hardware, comparing it favorably to the more complex graphics pipelines of modern games. Others delve into specific optimizations like precalculated lookup tables for trigonometry and the use of binary space partitioning (BSP) for efficient rendering. The small size of the game's assets and levels are also noted as contributing to its quick loading times and performance. One commenter mentions that Carmack's careful attention to performance, combined with his deep understanding of the hardware, resulted in a game that pushed the limits of what was possible at the time. Another user expresses appreciation for the clean and understandable nature of the original source code, making it a great learning resource for aspiring game developers.
Someone has rendered the entirety of the original Doom (1993) game, including all levels, enemies, items, and even the intermission screens, as individual images within a 460MB PDF file. This allows for a static, non-interactive experience of browsing through the game's visuals like a digital museum exhibit. The PDF acts as a unique form of archiving and presenting the game's assets, essentially turning the classic FPS into a flipbook.
Hacker News users generally expressed amusement and appreciation for the novelty of rendering Doom as a PDF. Several commenters questioned the practicality, but acknowledged the technical achievement. Some discussed the technical aspects, wondering how it was accomplished and speculating about the use of vector graphics and custom fonts. Others shared similar projects, like rendering Quake in HTML. A few users pointed out potential issues, such as the large file size and the lack of interactivity, while others jokingly suggested printing it out. Overall, the sentiment was positive, with commenters finding the project a fun and interesting hack.
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https://news.ycombinator.com/item?id=43908220
Hacker News users discuss the proposed taxonomy for rendering engines, mostly agreeing that it's a useful starting point but needs further refinement. Several commenters point out the difficulty of cleanly categorizing existing engines due to their hybrid approaches and evolving architectures. Specific suggestions include clarifying the distinction between "tiled" and "immediate" rendering, addressing the role of compute shaders, and incorporating newer deferred rendering techniques. The author of the taxonomy participates in the discussion, acknowledging the feedback and indicating a willingness to revise and expand upon the initial classification. One compelling comment highlights the need to consider the entire rendering pipeline, rather than just individual stages, to accurately classify an engine. Another insightful comment points out that focusing on data structures, like the use of a G-Buffer, might be more informative than abstracting to rendering paradigms.
The Hacker News post "A Taxonomy for Rendering Engines" sparked a modest discussion with a handful of comments, primarily focusing on clarifying terms and offering alternative perspectives on categorizing rendering engines.
One commenter pointed out the frequent misuse of the term "rasterization" within the 3D graphics community. They argue that the term should specifically refer to the process of converting primitives into fragments, not the broader pipeline that includes fragment shading and other operations. They suggest "scan conversion" as a more appropriate term for the full process of creating a 2D image from 3D geometry. This comment sparked a brief exchange where another user agreed with the distinction, highlighting how the term "rasterization" can conflate different stages of the rendering pipeline.
Another commenter questioned the placement of signed distance field rendering within the taxonomy. They suggested it's more of an acceleration structure rather than a fundamental rendering technique, comparing it to techniques like bounding volume hierarchies. This comment prompted the author of the original article to respond and clarify their reasoning. They explained that signed distance fields can be considered a rendering technique due to its ability to represent geometry implicitly and because the rendering process inherently involves sampling and evaluating the distance field. They acknowledge that SDFs can also be used as acceleration structures but emphasize their distinct use as a rendering technique in certain contexts.
Furthermore, there was a discussion around ray tracing versus path tracing, with one commenter seeking clarification on their relationship. The author of the article explained that path tracing is a specific type of ray tracing algorithm that simulates global illumination by recursively tracing light paths. They also clarified that ray tracing isn't solely for photorealistic rendering, highlighting its use in non-photorealistic rendering techniques as well.
A different commenter proposed an alternative way of categorizing rendering engines based on their shading model, specifically highlighting physically-based rendering and the distinction between local and global illumination models. This suggests a different axis for classifying renderers beyond the core techniques discussed in the original article.
Finally, a commenter touched on the complexity of classifying modern rendering engines, noting that many combine multiple techniques, such as using rasterization for primary visibility and ray tracing for select effects. This comment underlines the limitations of strict categorization and the evolving nature of rendering technologies.