Pekka Väänänen
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pekkavaa.bsky.social
Pekka Väänänen
@pekkavaa.bsky.social
1.1K followers 360 following 220 posts
Avid reader, computer graphics fan and atmospheric jungle beats enjoyer. Demoscene: cce/Peisik.

Blog at https://30fps.net/
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pekkavaa.bsky.social
Pekka Väänänen @pekkavaa.bsky.social · Oct 22
Hello I'm Pekka and I do experiments in computer graphics and machine learning. I mostly post about my coding projects, my blog or books I'm reading. I read a lot.

For the last couple of years I've gotten into #N64 coding. It's great for low-level graphics! I also keep an eye on #demoscene stuff.
A diagram of my fractal landscape renderer's inner workings: trees get spawn on a staggered grid. The trees are rendered as anti-aliased poinnn based on impostor depth maps. My Nintendo 64 occlusion culling experiment. Running in ares emulator so it's optimistically 60 fps because it has infinite fillrate. Still worth it on hardware though but maybe 25 fps :) A diagram of an iterative neural network that colors and stylizes G-buffer inputs. Based on Neural Cellular Automata (NCA) by Alexander Mordvintsev. Left: original monochrome Mona Lisa bitmap. Right: Least squares optimized tessellated version with linear interpolation.
pekkavaa.bsky.social
The Wikipedia page on Color appearance models at en.wikipedia.org/wiki/Color_a... surprisingly good: to the point but still feels comprehensive. Includes a quick comparison of different perceptual color spaces.
Color appearance model - Wikipedia
A color appearance model (CAM) is a mathematical model that seeks to describe the perceptual aspects of human color vision, i.e. viewing conditions under which the appearance of a color does not…
en.wikipedia.org
November 17, 2025 at 8:32 AM
Reposted by Pekka Väänänen
mmalex.bsky.social
via the magic of laion_clap embeddings and umap, my live coding thingy has a sample browser at last!
October 31, 2025 at 6:27 PM
pekkavaa.bsky.social
What if Doom's "colormap" was computed in Oklab instead of RGB?

A short article about it on my site: 30fps.net/pages/doom-o...
A Doom screenshot using a slightly more accurate colormap for lighting. Of course differences to the original become apparent only in a side-by-side comparison. A crop comparison of the earlier image. On the left, the original has bright grey lines in a dark area. In the new version on the right, the lines are gone, making the image more even.
October 30, 2025 at 8:32 AM
Reposted by Pekka Väänänen
hillsguy.bsky.social
Silent Hill 4 uses interesting volumetric light / light glare approximation.
Instead of drawing sprites at each light source, full-screen subdivided plane with procedural vertex colors is rendered and blended with game frame.
#gamedev
October 29, 2025 at 12:53 AM
pekkavaa.bsky.social
Relatable😑
From: doomwiki.org/wiki/Carmack...
The line in question: github.com/linguica/dmu...
Carmack's typo was a minor bug in dcolors.c, a program written by John Carmack in 1992 during early development of Doom. To generate the invulnerability colormap, Carmack converted each color in the palette to a gray scale value using a standard formula, where the gray scale value equals red*0.299 + green*0.587 + blue*0.114. In the utility, Carmack accidentally wrote 0.144 instead of 0.114, meaning that the invulnerability colormap converts all blues to be slightly too dark.[1] Since the invulnerability colormap inverts the gray scale palette, this means the gray scale colors converted from blue are calculated as brighter than they should be, and so become darker than they should be when the palette is inverted.
October 27, 2025 at 8:32 AM
pekkavaa.bsky.social
A new article: Why CIELAB doesn’t improve median cut

It's a common misconception that CIELAB will instantly improve palettes produced by the median cut algorithm. Unfortunately it's not that simple.

📜 30fps.net/pages/median...

It gets pretty technical but I added some context to the intro.
This graph shows how eager each color space is to minimize lightness error. The X-axis represents median cut’s splits as it works its way through clusters until all palette colors have been found. The Y-axis shows the sum of squared lightness errors of the whole image, measured as CIELAB’s L∗. I believe the low lightness weight is the main reason why median cut doesn’t work better in unscaled CIELAB than in sRGB.
October 24, 2025 at 12:50 PM
pekkavaa.bsky.social
Wow I didn't know Python has cute chained comparisons: "e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once (but in both cases z is not evaluated at all when x < y is found to be false)."

docs.python.org/3/reference/...
6. Expressions
This chapter explains the meaning of the elements of expressions in Python. Syntax Notes: In this and the following chapters, extended BNF notation will be used to describe syntax, not lexical anal...
docs.python.org
October 23, 2025 at 11:52 AM
pekkavaa.bsky.social
A fun look into Source 2's precomputed visibility from a mapper's perspective: www.youtube.com/watch?v=XLT2... It's not a BSP anymore but an octree whose nodes get grouped into clusters. Spoiler: Visleaks can still happen😀
CS2 Mapping Academy #10 - VIS Optimization (Counter Strike 2)
VIS is one of the most important facets of Source 2 level design. Learning how the engine optimizes your maps is important so that everyone can enjoy it! Learn how to take control of VIS in this…
www.youtube.com
October 21, 2025 at 11:52 AM
pekkavaa.bsky.social
A cool collection of monitor and sensor filter subpixel patterns geometrian.com/resources/su...
Subpixel Zoo: A Catalog of Subpixel Geometry
Display devices show color by illuminating small flat-color 'subpixels'—typically red, green, blue. They can be arranged in many ways. This page intends to be an exhaustive gallery of all subpixel…
geometrian.com
October 15, 2025 at 5:56 PM
pekkavaa.bsky.social
New article on my site: Better sRGB to greyscale conversion

The commonly used greyscale formula is slightly off when computed in gamma space but can it be fixed?

📜 30fps.net/pages/better...
A four-pane comparison of different formulas for greyscale conversion. Top row: Linear sRGB (the correct way to do it), Gamma sRGB (the somewhat wrong "luma" formula). Bottom row: CIELAB L* (a high quality option), and the new alternative gamma-space version. Careful inspection shows the "Gamma sRGB" case is slightly dimmer at points than the others. A quote from “Principles of Digital Image Processing” by Wilhelm Burger and Mark J. Burge. It shows weights that are a better fit for gamma-space greyscale conversion.
October 13, 2025 at 5:56 PM
pekkavaa.bsky.social
My new visualization for color quantization algorithm execution, though still unfinished. Attached is the result for a simple 12-color median cut. Each box contains a subset of image colors with the X-axis as a chosen sort axis; Y is PCA for plotting. See how e.g. box 3 has unwanted greens in it.
A top-down hierarchical color quantization routine shown as a binary tree. The algorithm starts from the top box 1 that contains all image colors and continues splitting the box with the greatest error (in this case just max volume) into color subsets. Each box is split at the median, shown in red. Splitting stops when the requested number of colors has been reached. The mean colors of the leaf nodes at the bottom define the final 12-color palette. The final image and its palette (top right). I chose a purposefully primitive algorithm as a demonstration and the colors are a bit greyish and dim because of it.
October 7, 2025 at 7:32 AM
Reposted by Pekka Väänänen
zeux.io
New blog post! In "Billions of triangles in minutes" we'll walk through hierarchical cluster level of detail generation of, well, billions of triangles in minutes. Reposts welcome!

zeux.io/2025/09/30/b...
September 30, 2025 at 5:40 PM
pekkavaa.bsky.social
I wrote a simple box collision resolution code today and made the classic mistake of not checking if box_a != box_b before testing for overlap. This was the bug that made me post my first programming question online 20 years ago or so! I was unaware of the <> Basic "not equals" operator at the time.
October 3, 2025 at 5:56 PM
pekkavaa.bsky.social
Tried to be clever with some NumPy array partitioning code and exchange two values with the "x[i], x[j] = x[j], x[i]" idiom. Nope: got to use "x[[i,j]] = x[[j, i]]" instead, see stackoverflow.com/a/47951813
Swap two values in a numpy array.
Is there something more efficient than the following code to swap two values of a numpy 1D array? input_seq = arange(64) ix1 = randint(len(input_seq)) ixs2 = randint(len(input_seq)) temp = input...
stackoverflow.com
September 26, 2025 at 11:52 AM
pekkavaa.bsky.social
A neat little paper from 2006 "A Median Cut Algorithm for Light Probe Sampling" where an environment map is compressed to a set of point lights using the median cut algorithm. Seems like a precursor to another 2007 paper where others cast the task as density estimation.
Figure 1: The Grace Cathedral light probe subdivided into 64 regions of equal light energy using the median cut algorithm. The small circles are the 64 light sources chosen as the energy centroids of each region; the lights are all approximately equal in energy. From Paul Debevec, "A Median Cut Algorithm for Light Probe Sampling" Comparison of median cut results using an HDRI and LDRI of memorial HDRI. a The memorial LDRI. b Median cut result, 1024 light sources generated starting from a LDRI. c Median cut result, 1024 light sources generated starting from a HDR From F. Banterle et al. "A framework for inverse tone mapping"
September 24, 2025 at 5:56 PM
Reposted by Pekka Väänänen
hiddenasbestos.bsky.social
Got my flight sim taking keyboard input and using that to drive the aerodynamic control surfaces. One step closer to take-off! #gamedev #flightsim #physics 🛩️
September 18, 2025 at 1:09 PM
Reposted by Pekka Väänänen
n64brew.bsky.social
N64brew user @boxingbruin.bsky.social continues to showcase more work that they've done for their Pickle64 project, their action-RPG platformer hybrid with dark souls-like boss fights.
September 14, 2025 at 11:36 AM
pekkavaa.bsky.social
There's a classic color transfer technique from 2001: convert source and target image to a decorrelated color space (Oklab works fine), make target's mean and stddev match the source, convert back to RGB. Using a palette image as a target is no problem :)

Paper: home.cis.rit.edu/~cnspci/refe...
A diagram showing three images: the Source, a crop from Big Buck Bunny; the target image, the PICO-8 palette; and the result image. The result image's color distribution has been moved to match the target. Paper reference: "Color Transfer Between Images" Reinhard et al. 2001.
September 10, 2025 at 7:32 AM
pekkavaa.bsky.social
A short article on mapping pixel colors to the PICO-8 palette in the CAM16-UCS color space. Surprisingly, it didn't do much better than Oklab, which is derived from CAM16.

📜 30fps.net/pages/percep...
A four-pane comparison of pixel mapping results in CAM16-UCS, Oklab, and the CIELAB colorspace (HyAB distance function). Top right is the input image.
September 8, 2025 at 11:52 AM
pekkavaa.bsky.social
Got familiar with NumPy's structured arrays today. It's basically an Array Of Structs, where fields can of course be different types. Could be useful with binary files, but I used it to organize code. Adding a "record array" allows a nice `colors.r` access syntax.

numpy.org/doc/stable/u...
# First deduplicate the colors unique_colors, counts = deduplicate_colors(img.reshape(-1, 4)) # Create a structured array so that we can have float RGBA colors, per color weight and # the original RGBA8 color accessible and sortable with a single index. ColorRGBA = np.dtype([ ('r', 'f4'), ('g', 'f4'), ('b', 'f4'), ('a', 'f4'), ('weight', 'f4'), ('original', 'u4'), ]) colors = np.rec.array(np.zeros(unique_colors.shape[0], dtype=ColorRGBA)) colors.r = unique_colors[:, 0] / 255.0 colors.g = unique_colors[:, 1] / 255.0 colors.b = unique_colors[:, 2] / 255.0 colors.a = unique_colors[:, 3] / 255.0 colors.weight = counts / num_total colors.original = unique_colors.view(np.uint32).reshape(-1) # Scale the channels to weight luminance more when picking a split-plane axis. # This is why its convenient to store the original RGBA8 color: the final step # that averages colors for the palette doesn't need to know about this transform. colors.r *= 0.30 colors.g *= 0.59 colors.b *= 0.11 colors.a *= 0.50
September 3, 2025 at 6:52 PM
Reposted by Pekka Väänänen
mjp123.bsky.social
Some fun with shader-based debug drawing: here I'm drawing an arrow for each path taken in the path tracer, starting with the pixel under the mouse cursor.
August 31, 2025 at 11:10 PM
pekkavaa.bsky.social
I finally added alpha support to VariQuant. It took a lot of head-scratching to make it work with both RGB and L*a*b*😅 I premultiply the alpha and handle it like the other color channels. For RGBA color distance I'm using Kornel Lesiński's clever formula: stackoverflow.com/a/8796867
The screenshot shows the "VariQuant" tool interface with a preview panel displaying an image named "boom.png" The interface includes settings for the number of colors, cut order, split plane, split position ("Mean" is chosen), color space for palette design and pixel mapping, averaging, luminance-scale, and K-means iterations. File operation buttons for opening, exporting, canceling, and generating palettes are also visible.
August 27, 2025 at 5:56 PM
pekkavaa.bsky.social
Gamma correction seems to be one of those things where the more you read the less you know. Is it really true that the NTSC standard assumes a CRT gamma of 2.5 but encoding is done with 1/2.2 instead to add a little contrast boost? From Charles Poynton's 2002 article at poynton.ca/notes/colour...
A screenshot of a chapter in the linked article with the following text: "Does NTSC use a gamma of 2.2? Television is usually viewed in a dim environment. If an images's correct physical luminance is reproduced in a dim surround, a subjective effect called simultaneous contrast causes the reproduced image to appear lacking in contrast, as demonstrated above. The effect can be overcome by applying an end-to-end power function whose exponent is about 1.1 or 1.2. Rather than having each receiver provide this correction, the assumed 2.5-power at the CRT is under-corrected at the camera by using an exponent of about 1/2.2 instead of 1/2.5. The assumption of a dim viewing environment is built into video coding. " There's also and a visual test diagram with two columns. The left column has three squares in a vertical arrangement, each with varying shades of gray, transitioning from light to dark. The right column also has three squares in a vertical arrangement, each with the same shades of gray as the left column, but with a black background behind them. It looks like the one on the right with a black background has less contrast.
August 26, 2025 at 5:56 PM
pekkavaa.bsky.social
I've been improving my "VariQuant" color quantization tool. It now supports more color spaces, locally optimal cuts that guarantee the next color cluster split is the one that gives greatest decrease in error, luminance weight scaling, HyAB distance, A/B toggle, and palettes can be saved as PNGs :)
Screenshot of VariQuant with a still from the movie 2001: Space Odyssey. Palette file has been exported from the tool as a PNG. The palette is sorted horizontally by lightness and vertically by hue.
August 22, 2025 at 5:56 PM
Reposted by Pekka Väänänen
zeux.io
meshoptimizer v0.25 is out! Featuring new simplification function that optimizes positions and attributes for appearance, experimental permissive mode to simplify faceted regions with selective seam preservation, regularization option for improved tessellation quality and deformation, multiple ...
August 20, 2025 at 3:56 PM