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Software rendering in 500 lines of bare C++
- t1234s 3mo agoI jumped when the first image loaded on the page.. didn't expect that.
- hnlmorg 3mo agoWhat image was that? The first image I get is a headshot. Personally I’d have gone with a teapot as my demo but I don’t see anything shocking about the model the author chose.
- mito88 3mo ago> I jumped when the first image loaded on the page.. didn't expect that. mbappe'?
- fleroviumna 3mo ago[dead]
- bob1029 3mo agoI wish we could have just one of these tutorials properly cover the concern of triangle clipping. This is the part that I struggle with the most in a software renderer. If you are going to be building a practical one, this is something you will eventually have to deal with, even for super basic scenes. Any time geometry intersects the view frustum you need to clip those triangles.
- deleted 3mo ago[deleted]
- ggambetta 3mo agoI have a whole chapter on that! https://gabrielgambetta.com/computer-graphics-from-scratch/11-clipping.html https://gabrielgambetta.com/computer-graphics-from-scratch/1...
- aninteger 3mo agoSorta unrelated but I really enjoy (I don't want to use the past tense as I often refer back to it) your article on Emulator Backed Remakes (https://gabrielgambetta.com/remakes.html https://gabrielgambetta.com/remakes.html). Thanks!
- ggambetta 3mo agoThanks for saying that :) Have you built something based on that idea? I still haven't, but I'm thinking on throwing some Claude at it for the most mechanical parts.
- yunnpp 3mo agoI bought and I am reading through your book as I build a sw rasterizer. On the chapter of clipping, it was not entirely clear to me how many planes you clip against and how many triangles result. Presumably if you clip against all 6 planes, you get 3+6-2 = 7 triangles in the worst case, which is kind of annoying. However, if you're going to use the AAAB triangle raster method as described in this HN post, then it seems there's no need to clip against left/right/top/bottom planes of the frustum, since it is simpler to just clip the screen-space AABB of the triangle instead. So one just needs to clip against near/far. This is simpler and faster. I was curious if you had given any thought on that, or if you plan on working on a second book with more details on these nuances.
- ggambetta 3mo agoMy book tries to be as accessible as possible; a high schooler with little to no knowledge of linear algebra should be able to understand all of it. So in every case I've chosen simplicity (code and/or conceptually) over performance, but without sacrificing correctness. Not always an easy balancing act! I would not recommend anyone to write a production rasterizer using the algorithms in my book. This website seems more performance-focused (Bresenham is the obvious choice to draw lines, for example). Specifically about clipping, you can ignore all the planes except the near plane, and everything will be fine. You'll try to draw more pixels outside the canvas but that's just slow, not problematic. The near plane does protect you from divisions by zero and from points with negative Z, which project upside down and mess things up.
- thechao 3mo agoYou only need to clip triangles is you're worried about attribute interpolation for very large triangles. There's two ways to handle this: (1) discard (fast but not a great user experience); or, (2) primitive synthesis. Just frustum clipping is enabled by point picking in the local tile. Primitive synthesis requires some FP kung fu; but, is easiest done in barycentric space against a reverse transformed clipping rectangle. This lets you carefully control clip rounding error using either doubles or (better) fixed point. Abrash likes to use integer fixed point, but that is historical — modern fixed point can be handled with careful control of the fp unit in the mantissa. The major issue is regenerating the Z and the 1/Z values for the new vertices of the synthesized primitives. Everything else should flow down the pipe naturally, assuming a deferred attribute synthesis rasterizer. There are examples in the open source version of my rasterizer: OpenSWR.org.
- delta_p_delta_x 3mo agoI'm clearly super old-school when it comes to rasterisation, and a lot of this has flown above my head. I have a ton of questions; I hope you can answer them. > (1) discard (fast but not a great user experience) What are we discarding here, and why is it fast but not a great user experience? > (2) primitive synthesis I assume this is retriangulating clipped triangles that are now no longer triangles? > reverse transformed clipping rectangle Which spaces does this reverse transformation map from and to? I assume the clipping rectangle here is the triangle's AABB in raster space (or as you say, barycentric space). > integer fixed point, but that is historical — modern fixed point can be handled with careful control of the fp unit in the mantissa So we are no longer doing 16.16 fixed point, but tweaking the FP representation itself? > The major issue is regenerating the Z and the 1/Z values for the new vertices Why is this a major issue? > deferred attribute synthesis rasterizer I assume this means attributes are perspective-correct interpolated in raster space.
- ack_complete 3mo agoMy own knowledge of GPU rasterization may be dated, but IIRC GPUs tend to rely on guard band clipping up to a guard band threshold before using geometric clipping. The guard band clipping involves rejecting 2D coarse rasterization blocks that are fully outside of the scissor rect. This is just a quick rectangle check, but the tradeoff is that a larger guard band means more GPU time lost in over-rasterization and potential higher precision requirements for rasterization values (which could be fixed point). Beyond the guard band, the triangles are clipped in floating point against the frustum clip planes.
- Sharlin 3mo agoMy renderer attempts always got stuck on the "should implement clipping" phase too, until I finally bit the bullet and managed to write a working one without much effort, independently "rediscovering" the Sutherland–Hodgman algorithm [1] as I found out later (googling it beforehand would've been cheating, of course). The algorithm itself is fairly straightforward and intuitive, I think the biggest mental block is the weirdness of the projective space and working with homogeneous coordinates (actually the only frustum plane that you have to clip against in P₃(ℝ) is the front plane, the rest could be clipped after the perspective division, but no reason not to do it all at the same time while you're at it). The plane equations in the clip space are super simple, basically the six equations of the form ax + by + cz = w simplify to x = ±w y = ±w z = ±w. Meaning, for example, that if the x coordinate of your vertex is greater than the w coordinate, that vertex is outside the right clipping plane. The Sutherland–Hodgman itself goes something like this: # Returns true if point is inside the half-space defined by plane def point_inside_plane(point, plane) -> bool: # single dot product, can be further simplified # Returns t such that the edge (p1, p2) intersects plane at lerp(t, p1, p2) def edge_intersect_plane(edge: (Point, Point), plane) -> float: # single dot product, can be further simplified # Given the vertices of a simple polygon and a plane, # returns the part of the polygon fully inside the plane def clip_against_plane(poly: [Vertex], plane): let result: [Vertex] = [] let [(v_1, v_2), (v_2, v_3), ..., (v_n, v_1)] = poly.edges() for each (v_i, v_j) of the edges: let i_inside = point_inside_plane(v_i, plane) let j_inside = point_inside_plane(n_j, plane) if i_inside and j_inside: # v_j will be pushed on the next iteration! result.push(v_i) else if not i_inside and not j_inside: pass # Nothing to do! else: # One is inside, the other is not, we have to clip let t = edge_intersect_plane((v_i.pos, v_j.pos), plane) # Synthetize a new vertex straddling the plane let v_new = Vertex( pos = lerp(t, v_i.pos, v_j.pos), # For each vertex attribute attrib = lerp(t, v_i.attrib, v_j.attrib) ) if i_inside: result.push(v_i); result.push(v_new) # discard v_j else: result.push(v_new); result.push(v_j) # discard v_i return result Then you just call this for all the planes so that the output of one call becomes the input for the next call! The end result of this process is a convex polygon (of at most nine vertices for a triangle against six planes), which can be trivially triangulated. You can make the whole process faster by precomputing so-called outcodes which allow you to avoid clipping triangles known to be entirely outside at last one plane, or entirely inside every plane. [1]: I. Sutherland and G. Hodgman. 1974. "Reentrant polygon clipping." Communications of the ACM, Volume 17, Issue. Available: https://dl.acm.org/doi/10.1145/360767.360802 https://dl.acm.org/doi/10.1145/360767.360802
- articulatepang 3mo agoI went through this a few months ago in Rust. I wrote all the code by hand, no LLMs. Then I went ahead and added a small "game" on top, plus some special effects like pixelization shaders and chromatic aberration at the edge of a flashlight. https://github.com/kshitijl/tinyrenderer-rs https://github.com/kshitijl/tinyrenderer-rs if anyone is interested! The repo has lots and lots of in-progress screenshots so you can see the renderer come to life, plus all the hilarious visual bugs along the way. I learned a lot! My biggest lesson, other than the specifics of how rendering works, was that modern CPUs are really fast: a single-threaded CPU renderer can definitely run an interactive 3D game with some fancy special effects.
- 0x1ceb00da 3mo agoWhy does it pull in wgpu if it's a software renderer?
- deleted 3mo ago[deleted]
- grovesNL 3mo agoIn this case wgpu is just providing the surface texture for the window that the software rendered pixels are drawn into.
- chrisjj 3mo ago"Comments An error occurred: API rate limit already exceeded "
- nkanaev 3mo agoThis resource, along with Mathematics for Computer Graphics by John Vince [1], was truly indispensable when I wrote my own software renderer [2]. This was long before LLMs, so the whole process took me at least a couple months - most of it trying to wrap my head around math behind computer graphics and tracking down C segmentation faults. Fun times. [1]: https://www.amazon.co.uk/Mathematics-Computer-Graphics-John-Vince-ebook/dp/B000T09X0E/ https://www.amazon.co.uk/Mathematics-Computer-Graphics-John-... [2]: https://github.com/nkanaev/tipsy https://github.com/nkanaev/tipsy
- DatCodeMania 3mo agoIs the source of yours public anywhere? I'd like to take a look.
- mentos 3mo agoHow many hours a day over the couple months?
- espetro 3mo agoFinally an engineering feat that's not built in Rust
- uncivilized 3mo agoI thought this would be something new but it’s just ssloy’s tinyrenderer. Article should have a date since it’s old as dirt
- mootdentures 3mo agoJust because you've seen something before doesn't mean it isn't new for some readers! This is my first time seeing it
- CyberDildonics 3mo agoThey just said it should have a date and it should.
- anthk 3mo agoThere was a software rendered game in vein of Tomb Raider 1 graphics for both DOS and Unix, but I can't remember its name. It was an exploration game, modern, a bit cyberpunkish, in 3D.
- fithisux 3mo agoThis is a very good article.
- layla5alive 3mo agoIs something broken on mobile? It has code for writing a few pixels to a tga and then shows you how to clone their repo and then shows some photos... There is.. no real article..? Edit: Ah: there's a quiet hamburger menubar. The page really should have forward/next/toc links.
- Sharlin 3mo agoI've been wanting to write a series of articles exactly like this for a long time. Good that someone else has done it now =D
- brcmthrowaway 3mo agoHow does this differ from POVRay?
- 42days 3mo agoPOVray is a declarative language used to render raytraced scenes. This is a tutorial that demonstrates how the rasterization technique works from a programmatic perspective.
- 0x1ceb00da 3mo agoOk I'm following along but how do I view the tga files that this program produces? Windows can't open them.
- AlexeyBrin 3mo agoYou can replace the tga with bmp which is natively supported by Windows and not difficult to implement (if you prefer to use a C library look for stb libs).
- mhoela 3mo agoIrfanview?
- pjmlp 3mo agoNow that is an application I don't see in a long time, it used to be part of my default set of stuff to install on a new Windows PC.
- atan2 3mo agoon the topic of software rendering, im surprised how little gustavo pezzi's lectures get mentioned here on hacker news.
- AlexeyBrin 3mo agoGustavo's lectures are great! I work through his Compiler lectures now and I bought the 3D renderer course too.
- gustavopezzi 3mo agoGlad to hear that! All the topics are incredibly fun to play around with.
- bananaboy 3mo agoFor anyone wondering, Gustavo runs https://pikuma.com/ https://pikuma.com/ which has a host of lectures on a variety of topics from PlayStation 1 programming to maths to triangle rasterisation.
- gustavopezzi 3mo agoThat's right. :-)
- gustavopezzi 3mo agoHey! Gustavo here. Thanks for the mention. The 3D software renderer course is still one of my favorites, even though it was one of the first ones I've published. I recently re-recorded the chapter on perspective projection matrix.
- whartung 3mo agoIs the Foley/Van Dam book still a go to resource for this? It seems it was updated in 2013, but, honestly, I’m more familiar with the ‘82 edition that was dedicated to 2D. Back in the day, it was The Book for computer graphics.
- pjmlp 3mo agoI also learnt with the second edition, I own the last one from 2013, it is alright. The languages have evolved across editions, from Pascal, to C, to C and C++, and a bit of C# as well on the last one. Naturally it misses on several new concepts, however I would assert it has quite valuable content.
- momocowcow 3mo agoI haven't looked at my copy in years. To me, the book is a peculiar encyclopedia with some historical importance. I found the course note from this github to be a good refresher on the subject. While the repo source code style is distasteful to me and their old-school rasteriser in the course is too naive and unoptimal, it's still a better read than Foley I'd assume :)
- xgkickt 3mo agoIn a fit of 90s nostalgia I’ve also been going back to software rendering, though I’m doing a hybrid of 2D style CLUT banks with a more modern binned triangle and barycentric technique. Since I’m sticking to a fixed pipeline look, I’ve been amazed at just how many triangles one can push even with a fairly naive draw function.
- jis7gdhshs 3mo ago[flagged]
- pjmlp 3mo agoFor whatever reason you planted this on your head, there are people that can provide professional help.
- uiiqhsgxg 3mo ago[dead]
- pjmlp 3mo agoAgain, seek professional help.
- uisodnvjjsjsh 3mo ago[dead]
- killyourselfbit 2mo ago[dead]
- Wintermute21 3mo agoI actually submitted my first PR against this repo in forever because I found a bug in how macOS handles OpenMP. Cool article and code.
- smolder 3mo agoThere's basically no such thing as "bare C++" anymore. On any modern machine you are relying on piles of code. You can't just write to registers to edit vram and output video like on some 80s computer. It all happens on top of a thick stack of APIs, drivers and firmware.
- Zfyuchar 3mo agoThat's impressive. Building a renderer from scratch sounds like one of those projects that teaches you far more than following tutorials ever could. I'll definitely check out the screenshots.