Beautiful, open source, WebGPU-based charting library - ChartGPU/ChartGPU
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uPlot maintainer here. this looks interesting, i'll do a deeper dive soon :)
some notes from a very brief look at the 1M demo:
- sampling has a risk of eliminating important peaks, uPlot does not do it, so for apples-to-apples perf comparison you have to turn that off. see https://github.com/leeoniya/uPlot/pull/1025 for more details on the drawbacks of LTTB
- when doing nothing / idle, there is significant cpu being used, while canvas-based solutions will use zero cpu when the chart is not actively being updated (with new data or scale limits). i think this can probably be resolved in the WebGPU case with some additional code that pauses the updates.
- creating multiple charts on the same page with GL (e.g. dashboard) has historically been limited by the fact that Chrome is capped at 16 active GL contexts that can be acquired simultaneously. Plotly finally worked around this by using https://github.com/greggman/virtual-webgl
> data: [[0, 1], [1, 3], [2, 2]]
this data format, unfortunately, necessitates the allocation of millions of tiny arrays. i would suggest switching to a columnar data layout.
uPlot has a 2M datapoint demo here, if interested: https://leeoniya.github.io/uPlot/bench/uPlot-10M.html
By huntergemmer 2026-01-2118:301 reply Really appreciate you taking the time to look, Leon - uPlot has been a huge inspiration for proving that browser charts don't have to be slow.
Both points are fair:
1. LTTB peak elimination - you're right, and that PR is a great reference. For the 1M demo specifically, sampling is on by default to show the "it doesn't choke" story. Users can set sampling: 'none' for apples-to-apples comparison. I should probably add a toggle in the demo UI to make that clearer.
2. Idle CPU - good catch. Right now the render loop is probably ticking even when static. That's fixable - should be straightforward to only render on data change or interaction. Will look into it.
Would love your deeper dive feedback when you get to it. Always more to learn from someone who's thought about this problem as much as you have.
By dapperdrake 2026-01-2213:411 reply Blind sampling like this makes it useless for real-world statistics of the kind your users care about.
And column-oriented data is a must. Look at Rlang's data frames, pandas, polars, numpy, sql, and even Fortran's matrix layout.
Also need specialized expicitly targetable support for Float32Array and Float64Array. Both API and ABI are necessary if you want to displace incumbents.
There is huge demand for a good web implementation. This is what it takes.
Am interested in collaborating.
By huntergemmer 2026-01-2215:05 Down. Hit me up!
Original Flot maintainer here.
I once had to deal with many million data points for an application. I ended up mip-mapping them client-side.
But regarding sampling, if it's a line chart, you can sample adaptively by checking whether the next point makes a meaningfully visible difference measured in pixels compared to its neighbours. When you tune it correctly, you can drop most points without the difference being noticeable.
I didn't find any else doing that at the time, and some people seemed to have trouble accepting it as a viable solution, but if you think about it, it doesn't actually make sense to plot say 1 million points in a line chart 1000 pixels wide. On average that would make 1000 points per pixel.
By PaulDavisThe1st 2026-01-2123:581 reply We routinely face this in the audio world when drawing waveforms. You typically have on the order of 10-100k samples per second, durations of 10s-1000s of seconds, and pixel widths of on the order of 1-10k pixels.
Bresenham's is one algorithm historically used to downsample the data, but a lot of contemporary audio software doesn't use that. In Ardour (a cross-platform, libre, open source DAW), we actually compute and store min/max-per-N-samples and use that for plotting (and as the basis for further downsampling.
By leeoniya 2026-01-221:22 > In Ardour (a cross-platform, libre, open source DAW), we actually compute and store min/max-per-N-samples and use that for plotting (and as the basis for further downsampling.
this is, effectively, what uPlot does, too: https://github.com/leeoniya/uPlot/issues/1119
By ghc 2026-01-224:23 > Original Flot maintainer here.
I discovered flot during my academic research career circa 2008 and it saved my ass more times than I can count. I just wanted to say thank you for that. I wouldn't be where I am today without your help :)
By leeoniya 2026-01-221:24 hey!
> But regarding sampling, if it's a line chart, you can sample adaptively by checking whether the next point makes a meaningfully visible difference measured in pixels compared to its neighbours.
uPlot basically does this (see sibling comment), so hopefully that's some validation for you :)
By dapperdrake 2026-01-2213:42 This is a good sampling transform to offer. Call it "co-domain awareness" or something.
By vlovich123 2026-01-2119:222 reply Is there any techniques using wavelet decomposition to decimate the high frequency component while retaining peaks? I feel like that's a more principled approach than sampling but I haven't seen any literature on it describing the specific techniques (unless the idea is fundamentally unsound which is not obvious to me).
By huntergemmer 2026-01-2119:363 reply Interesting idea - I haven't explored wavelet-based approaches but the intuition makes sense: decompose into frequency bands, keep the low-frequency trend, and selectively preserve high-frequency peaks that exceed some threshold.
My concern would be computational cost for real-time/streaming use cases. LTTB is O(n) and pretty cache-friendly. Wavelet transforms are more expensive, though maybe a GPU compute shader could make it viable.
The other question is whether it's "visually correct" for charting specifically. LTTB optimizes for preserving the visual shape of the line at a given resolution. Wavelet decomposition optimizes for signal reconstruction - not quite the same goal.
That said, I'd be curious to experiment. Do you have any papers or implementations in mind? Would make for an interesting alternative sampling mode.
By vlovich123 2026-01-2123:301 reply I don't. I just remember watching a presentation on it and it always struck me that wavelets are an incredibly powerful and underutilized technique for data reduction while preserving quality in a quantifiable and mathematically justifiable way.
I don't have any papers in mind, but I do think that the critique around visual shape vs signal reconstruction may not be accurate given that wavelets are starting to see a lot of adoption in the visual space (at least JPEG2000 is the leading edge in that field). Might also be interesting to use DCT as well. I think these will perform better than LTTB (of course the compute cost is higher but there's also HW acceleration for some of these or will be over time).
By dapperdrake 2026-01-2213:45 This might be because JPEG already does FFT/DCT.
By dapperdrake 2026-01-2213:441 reply Doesn't FFT depend at least on a "representative" sample of the entire dataset?
Sounds like what makes sql joins NP-hard.
By vlovich123 2026-01-244:03 No, FFT is perfectly information preserving by definition. Thats why there’s an inverse FFT operation that restores the original signal without any loss (well, modulo accumulated floating point error when working in the discrete instead of symbolic space).
By dapperdrake 2026-01-2213:43 This really depends on your problem domain.
> creating multiple charts on the same page with GL (e.g. dashboard) has historically been limited by the fact that Chrome is capped at 16 active GL contexts that can be acquired simultaneously. Plotly finally worked around this by using https://github.com/greggman/virtual-webgl
Sometimes I like to ponder on the immense amount of engineering effort expended on working around browser limitations.
By dapperdrake 2026-01-2213:45 Think of it as finally targeting a smartphone. People like beautiful pictures. And your phone is already in your hand.
Not much to add, but as a very happy uPlot user here - just wanted to say thank you for such an amazing library!!
By leeoniya 2026-01-2120:26 yw!
By sarusso 2026-01-2120:57 What I did in a few projects to plot aggregated (resampled) data without loosing peaks was to plot it over an area chart representing the min-max values before aggregating (resampling). It worked pretty well.
By Bengalilol 2026-01-228:071 reply One small thing I noticed: when you zoom in or out (or change the time span), the y-axis stays the same instead of adapting to the visible data.
By dapperdrake 2026-01-2213:47 Both are useful. With the y-axis staying the same there is a stable point of reference. Then you can see how sub-samples behave relative to your whole sample.
I wouldn't spend too much of your time deep diving - it's an AI slop project.
By fuckyah 2026-01-223:52 [dead]
By fuckyah 2026-01-223:52 [dead]
If you have tons of datapoints, one cool trick is to do intensity modulation of the graph instead of simple "binary" display. Basically for each pixel you'd count how many datapoints it covers and map that value to color/brightness of that pixel. That way you can visually make out much more detail about the data.
In electronics world this is what "digital phosphor" etc does in oscilloscopes, which started out as just emulating analog scopes. Some examples are visible here https://www.hit.bme.hu/~papay/edu/DSOdisp/gradient.htm
By huntergemmer 2026-01-2117:591 reply Great suggestion - density mapping is a really effective technique for overplotted data. Instead of drawing 1M points where most overlap, you're essentially rendering a heatmap of point concentration. WebGPU compute shaders would be perfect for this - bin the points into a grid, count per cell, then render intensity. Could even do it in a single pass. I've been thinking about this for scatter plots especially, where you might have clusters that just look like solid blobs at full zoom-out. A density mode would reveal the structure. Added to the ideas list - thanks for the suggestion!
You don't need webgpu for that. It's a standard vertex shader -> fragment shader pass with the blending mode set to addition.
Drawing lots of single pixels with alpha blending is probably one of the least efficient ways to use the rasterizer though. A good compute shader implementation would be substantially faster.
At 1M points it hardly makes a difference. Besides, 1 point -> 1 pixel mapping is good enough for a demo, but in practice it will produce nasty aliasing artifacts because real datasets aren't aligned with pixel coordinates. So you have to draw each point as a 2x2 square at least with precise shading, and we are back to the rasterizer pipeline. Edit: what actually needs to be computed is the integral of the points dataset over each square pixel, and that depends on the shape of each point, even if it's smaller than a pixel.
Aren't we at petaflops now with GPUs? 1M or even 1G points should be no issue if it renders to a framebuffer and doesn't go through mountains af JS framework rubbish followed by mountains of GTK/Qt/.NET rubbish.
By rustystump 2026-01-224:291 reply Not true. Fill rate and memory speed is still a huge bottleneck. The issue is not “rubbish” but memory speed. It is almost always memory speed, cache, ram, disk etc.
There is this misconception that if one uses js or c# to tell a gpu what to do it is somehow slower than rust. It only is if you crunching data but moving memory to the gpu and telling gpu to crunch is virtually identical.
PCIe 6.0 x16 delivers ~128 GB/s so the billion points can be loaded in milliseconds onto the GPU. The GPU's memory is much faster.
By rustystump 2026-01-228:23 Most consumers dont have that and at 60 fps you are already maxing it out and more assuming os is doing nothing else. Bandwidth even on gpus is still the bottleneck.
Even then, when u write to a framebuffer directly in the gpu if the locations of the points are not contiguous you are thrashing. Rendering points very fast is still very much about reducing the data set down to bypass all the layers of memory walls.
By dapperdrake 2026-01-2213:49 No difference for human visuals or no difference for discrete data or no difference for "continuous" f32 data?
By vanderZwan 2026-01-2119:281 reply That works if more overdraw = more intensity is all you care about, and may very well be good enough for many kinds of charts. But with heat map plots one usually wants a proper mapping of some intensity domain to a color map and a legend with a color gradient that tells you which color represents which value. Which requires binning, counting per bin, and determining the min and max values.
Emm.. no, you just do one render pass to a temp framebuffer with 1 red channel, then another fragment shader maps it to an RGB palette.
By vanderZwan 2026-01-229:241 reply Wait, does additional blending let you draw to temp framebuffers with high precision and without clamping? Even so you'd still need to know the maximum value of the temp framebuffer though.
That's what EXT_float_blend does. It's true, though, that you can't find the global min/max in webgl2. This could be done, theoretically, with mipmaps if only those mipmaps supported the max function.
By vanderZwan 2026-01-2312:231 reply Couldn't you do that manually with a simple downscaling filter? I'd be very shocked if fragment shaders did not have a min or max function.
Repeatedly shrinking by a factor of two means log2(max(width, height)) passes, each pass is a quarter of the pixels of the previous pass so that's a total of 4/3 times the pixels of the original image. Should be low enough overhead, right?
By akomtu 2026-01-2319:24 Sure, that will work, but it's log2 passes + temp framebuffers. As for overhead, I'm afraid it will eat a couple fps if you run it on every frame. In practice, though, I'm not sure that finding the exact maximum is that valuable for rendering: a good guess based on the dataset type will do. For example, if you need to render N points that tend to congregate in the center, using sqrt(N) as the heuristic for the maximum works very well.
By jsmailes 2026-01-228:34 That digital phosphor effect is fascinating! As someone who works frequently with DSP and occasionally with analogue signals, it's incredible to see how you can pull out the carrier/modulation just by looking at (effectively) a moving average. It's also interesting to see just how much they have to do behind the scenes to emulate a fairly simple physical effect.
By leeoniya 2026-01-2118:43 agreed, heatmaps with logarithmic cell intensity are the way to go for massive datasets in things like 10,000-series line charts and scatter plots. you can generally drill downward from these, as needed.
By dapperdrake 2026-01-2213:48 Good idea.
Add Lab-comor space for this though, like the color theme solarized-light.
Also add options to side-step red-green blindness and blue-yellow blindndess.
Right on time.
We’ve been working on a browser-based Link Graph (osint) analysis tool for months now (https://webvetted.com/workbench). The graph charting tools on the market are pretty basic for the kind of charting we are looking to do (think 1000s of connected/disconnected nodes/edges. Being able to handle 1M points is a dream.
This will come in very handy.
By huntergemmer 2026-01-2117:011 reply That's a cool project! Just checked out the workbench. I should be upfront though: ChartGPU is currently focused on traditional 2D charts (line, bar, scatter, candlestick, etc.), not graph/network visualization with nodes and edges. That said, the WebGPU rendering patterns would translate well to force-directed graphs. The scatter renderer already handles thousands of instanced points - extending that to edges wouldn't be a huge leap architecturally.
Is graph visualization something you'd want as part of ChartGPU, or would a separate "GraphGPU" type library make more sense? Curious how you're thinking about it.
By agentcoops 2026-01-2117:531 reply Really fantastic work! Can't wait to play around with your library. I did a lot of work on this at a past job long ago and the state of JS tooling was so inadequate at the time we ended up building an in-house Scala visualization library to pre-render charts...
More directly relevant, I haven't looked at the D3 internals for a decade, but I wonder if it might be tractable to use your library as a GPU rendering engine. I guess the big question for the future of your project is whether you want to focus on the performance side of certain primitives or expand the library to encompass all the various types of charts/customization that users might want. Probably that would just be a different project entirely/a nightmare, but if feasible even for a subset of D3 you would get infinitely customizable charts "for free." https://github.com/d3/d3-shape might be a place to look.
In my past life, the most tedious aspect of building such a tool was how different graph standards and expectations are across different communities (data science, finance, economics, natural sciences, etc). Don't get me started about finance's love for double y-axis charts... You're probably familiar with it, but https://www.amazon.com/Grammar-Graphics-Statistics-Computing... is fantastic if you continue on your own path chart-wise and you're looking for inspiration.
By huntergemmer 2026-01-2118:121 reply Thanks - and great question about direction. My current thinking: Focus on performance-first primitives for the core library. The goal is "make fast charts easy" not "make every chart possible." There are already great libraries for infinite customization (D3, Observable Plot) - but they struggle at scale.
That said, the ECharts-style declarative API is intentionally designed to be "batteries included" for common cases. So it's a balance: the primitives are fast, but you get sensible defaults for the 80% use case without configuring everything. Double y-axis is a great example - that's on the roadmap because it's so common in finance and IoT dashboards. Same with annotations, reference lines, etc. Haven't read the Grammar of Graphics book but it's been on my list - I'll bump it up. And d3-shape is a great reference for the path generation patterns. Thanks for the pointers!
Question: What chart types or customization would be most valuable for your use cases?
By agentcoops 2026-01-2118:361 reply Most of my use cases these days are for hobby projects, which I would bucket into the "data science"/"data journalism" category. I think this is the easiest audience to develop for, since people usually don't have any strict disciplinary norms apart from clean and sensible design. I mention double y-axes because in my own past library I stupidly assumed no sensible person would want such a chart -- only to have to rearchitect my rendering engine once I learned it was one of the most popular charts in finance.
That is, you're definitely developing the tool in a direction that I and I think most Hacker News readers will appreciate and it sounds like you're already thinking about some of the most common "extravagances" (annotations, reference lines, double y-axis etc). As OP mentioned, I think there's a big need for more performant client-side graph visualization libraries, but that's really a different project. Last I looked, you're still essentially stuck with graphviz prerendering for large enough graphs...
By huntergemmer 2026-01-2119:441 reply Ha - the double y-axis story is exactly why I want to get it right. Better to build it in properly than bolt it on later.
"Data science/data journalism" is a great way to frame the target audience. Clean defaults, sensible design, fast enough that the tool disappears and you just see the data.
And yeah, graphviz keeps coming up in this thread - clearly a gap in the ecosystem. Might be a future project, but want to nail the 2D charting story first and foremost.
Thanks for the thoughtful feedback - this is exactly the kind of input that shapes the roadmap.
By graphviz 2026-01-2120:49 Gratifying that it's still useful.
A lot of improvements are possible, based on 20 years of progress in interactive systems, and just overall computing performance.
By lmeyerov 2026-01-221:55 You may enjoy Graphistry (eg, pygraphistry, GraphistryJS), where our users regularly do 1M+ graph elements interactively, such as for event & entity data. Webgl frontend, GPU server backend for layouts too intense for frontend. We have been working on stability over the last year with large-scale rollout users (esp cyber, IT, social, finance, and supply chain), and now working on the next 10X+ of visual scaling. Python version: https://github.com/graphistry/pygraphistry . It includes many of the various tricks mentioned here, like GPU hitmapping, and we helped build various popular libs like apache arrow for making this work end-to-end :)
Most recently adding to the family is our open source GFQL graph language & engine layer (cypher on GPUs, including various dataframe & binary format support for fast & easy large data loading), and under the louie.ai umbrella, piloting genAI extensions
By MeteorMarc 2026-01-2118:10 Can you please comment about this trust listing? Are we talking the same thing?https://gridinsoft.com/online-virus-scanner/url/webvetted-co...
By wesammikhail 2026-01-2117:14 my 2 cents: I'm one of these people that could possibly use your tool. However, the website doesnt give me much info. I'd urge you to add some more pages that showcase the product and what it can do with more detail. Would help capture more people imo.
By losteric 2026-01-221:02 Does Cosmos.gl do what you need? https://cosmos.gl/?path=/docs/welcome-to-cosmos-gl--docs
Agreed. This is highly, highly useful. Going to integrate this today.
By huntergemmer 2026-01-2118:18 Awesome - let me know how it goes! Happy to help if you hit any rough edges. GitHub issues or ping me here.
By kqr 2026-01-227:51 Is this an open source Palantir?
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