Lomont.org

MinimalTicTacToe

Fri, 26 Jul 2024 07:50:18 -0400

Derivation of a minimal size tree for playing perfect tic tac toe

Correct alpha and gamma for image processing

Mon, 28 Aug 2023 18:40:19 -0400

This is a note on the correct usage of alpha blending, pre-multiplied alpha, gamma correction, and linear colors for image processing.

IOS PNG Errors

Sun, 23 Jul 2023 14:44:11 -0400

XCode corrupts PNG images for iOS builds. This post details the error.

Problems using SSIM for image quality comparisons

Sat, 24 Jun 2023 10:36:07 -0400

Variation among SSIM implementations make comparing results a mess. This version matches the output of the original, unlike most of those in common use as of 2023.

Accurate color conversions

Tue, 06 Jun 2023 07:12:30 -0400

This is a quick note for converting byte values colors in 0-255 back and forth to floating-point colors in 0-1 which avoids common errors.

Button debouncing and pattern matching

Tue, 22 Nov 2022 18:17:00 -0400

A robust, portable, extensible method for handling button presses when interfacing software and hardware.

A better quadratic formula algorithm

Sat, 27 Aug 2022 08:12:01 -0400

A robust algorithm for computing roots of quadratic equations, much better than common code.

Lomont floating point notes

Fri, 26 Aug 2022 08:07:00 -0400

Notes on floating point issues, including lists of facts and theorems useful for algorithm development.

Rtk Gps Project

Mon, 07 Dec 2020 20:25:57 -0500

I built a RTK-GPS gadget and wrote enough software to do basic GNS tasks such as finding distances, decoding GPS NMEA and RTCM messages, finding intersections, and doing boundary detection.

Chris Lomont's lines of code over time

Sun, 23 Jun 2019 12:10:43 -0400

Over decades I’ve written a lot of personal code. I made a bar chart race showing how many lines I’ve written in different languages over time.

Excel2007Bug

Thu, 06 Jun 2019 22:15:58 -0400

Summary

EvilNumbers

Thu, 06 Jun 2019 22:14:37 -0400

Summary

Chris Lomont's Geometric Algebra page

Thu, 06 Jun 2019 22:12:33 -0400

Summary

Chris Lomont's Finite Fields page

Thu, 06 Jun 2019 22:11:13 -0400

Summary

FourFours.nb

Thu, 06 Jun 2019 22:09:52 -0400

Summary

Chris Lomont's Superballs Page

Thu, 06 Jun 2019 22:08:06 -0400

Summary

Chris Lomont's LED Cube Page Videos

Thu, 06 Jun 2019 22:02:59 -0400

Summary

Chris Lomont's LED Cube Page Part 4

Thu, 06 Jun 2019 22:02:51 -0400

Summary

Chris Lomont's LED Cube Page Part 3

Thu, 06 Jun 2019 22:02:49 -0400

Summary

Chris Lomont's LED Cube Page Part 2

Thu, 06 Jun 2019 22:02:47 -0400

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Chris Lomont's LED Cube Page Part 1

Thu, 06 Jun 2019 22:02:45 -0400

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Chris Lomont's LED Cube Page

Thu, 06 Jun 2019 22:02:43 -0400

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Chris Lomont's PhotoMosaic Page

Thu, 06 Jun 2019 22:00:06 -0400

Summary

MiniCompress

Thu, 06 Jun 2019 21:59:45 -0400

Summary

G15Info

Thu, 06 Jun 2019 21:58:55 -0400

Summary

StockTrader

Thu, 06 Jun 2019 21:57:35 -0400

Summary

Chris Lomont's SimpleWinApp Page

Thu, 06 Jun 2019 21:56:13 -0400

Summary

Chris Lomont's Robotron 2084 Page

Thu, 06 Jun 2019 21:53:26 -0400

A page for Robotron 2084 hacking

HPCalc

Thu, 06 Jun 2019 21:52:57 -0400

Summary

Chris Lomont's AES Page

Thu, 06 Jun 2019 21:50:33 -0400

Summary

MoneySaver

Thu, 06 Jun 2019 21:45:39 -0400

Summary

MetaBalls

Thu, 06 Jun 2019 21:44:13 -0400

Summary

KnotSaver

Thu, 06 Jun 2019 21:42:53 -0400

Summary

Knots

Thu, 06 Jun 2019 21:41:52 -0400

Summary

Chris Lomont's MP3 Tag Editor

Thu, 06 Jun 2019 21:40:27 -0400

<h3>MP3 Tag editor! </h3>
<p>Here are some features and screenshots of my beta Tag Editor. <a href="/contact/">Let me know</a> what you think! This requires .NET 1.1 or higher. Click <a href="tedit.exe">here to download</a> it! (908K) </p>

Warning!

This software is BETA. Please do not use it on the only copy of your MP3 files. Edit your files with this, and once you are convinced it made the correct changes, commit them to your music collection. I use it on my files and have no problems, but your mileage may vary.

Chris Lomont's Sudoku Page

Thu, 06 Jun 2019 21:37:44 -0400

Summary

Chris Lommont's PacMan Page

Thu, 06 Jun 2019 21:35:56 -0400

Summary

Chris Lomont's Cross Sums page

Thu, 06 Jun 2019 21:34:26 -0400

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Chris Lomont's Lemmings Page

Thu, 06 Jun 2019 21:33:09 -0400

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Chris Lomont's Riddle Pages

Thu, 06 Jun 2019 07:55:47 -0400

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Chris Lomont's Riddle Pages

Thu, 06 Jun 2019 07:55:47 -0400

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Chris Lomont's Quantum Computing Seminar page

Thu, 06 Jun 2019 07:51:50 -0400

Summary

Chris Lomont's 51 Piece Burr Puzzle Solution

Thu, 06 Jun 2019 07:49:20 -0400

A solution to a nice 51 piece burr.

Chris Lomont's Puzzle Pics

Thu, 06 Jun 2019 07:49:20 -0400

Here’s a few of my puzzles

Ball1

Ball2

Burr1

Burr2

Burr3

Burr4

Burr5

Burr6

Burr7

Burr8

Chris Lomont's Laser Cut Torus Page

Thu, 06 Jun 2019 07:47:29 -0400

A laser cut torus

Chris Lomont's Seaham Project Page

Thu, 06 Jun 2019 07:46:07 -0400

An art installation in the UK

Chris Lomont's Laser Cut Truncated Icosidodecahedron Page

Thu, 06 Jun 2019 07:44:34 -0400

A lser cut polyhedron

Chris Lomont's Lego Walker Page

Thu, 06 Jun 2019 07:41:09 -0400

Summary

Chris Lomont's Real3D Plugin Page

Thu, 06 Jun 2019 07:39:26 -0400

Realsoft3D Lego Plugin

THIS IS ALL BETA! Will release when tested better.

Some sample output can be seen on the Clock I page.

An executable that converts a MLCAD file to a textfile is found here(200K). It takes a file for input, and outputs a file "name".txtx in C:\ right now. Will make more flexible later. Then place this DLL(73K) in the plugins directory of Real3D, and open the file.

Chris Lomont's Lego Clock page

Thu, 06 Jun 2019 07:36:37 -0400

A Lego clock

Chris Lomont's Burr Puzzle

Sun, 02 Jun 2019 19:41:07 -0400

Testing pics

The Lomont Burr

Here are the pictures of the Lomont Burr, a 2x3x4 burr which requires 3 moves before any piece can be removed.

Click on any pictures for larger versions.

The design of the puzzle

Here are two renderings of the puzzle, and a piece diagram and a solution, all generated by my custom software before I actually built a physical version. Here is a link to a rendered video of the puzzle disassembling.

Chris Lomont's TRS-80 Color Computer Page

Sun, 02 Jun 2019 18:55:31 -0400

256 color demo mode

Aug 2007

Here is an assembly file (with included comments) explaining a 256 color mode on the CoCo3 that may be suitable for games. It needs some more work to determine how fast one can animate with this method. Here is a *.dsk file with the assembled program. LOAD"A and then EXEC. The program shows the 256 color image, and the assembly file can also do a 240 color mode using a different palette that may be better for gaming.

Here are two images of the resulting palettes as displayed in Mathematica (where I attempted, unsuccessfully, to determine optimal palette values). The 240 color one is on the left, and the 256 color one is on the right.

Chris Lomont's Terms of Use Page

Sun, 02 Jun 2019 15:56:26 -0400

All content of this site is copyright Chris Lomont 1995-2020. You may not use material on this site for commercial uses withtout written permission. Anything on this site may be used for personal use, except where otherwise noted.

Chris Lomont's About Page

Sun, 02 Jun 2019 15:51:40 -0400

This is my personal website, where I can vent some crazy ideas, give away some software, and have my own internet real estate.

For starters, check out the 3D LED cube project, one of my current playthings.

This page has an overview of the things you may find here. Explore, and turn out the lights when you leave.

Computers

Ever since third grade I have been fascinated with computers, electronics, and robots. Most of what I do professionally and for hobbies revolve around this. My most time consuming hobby is programming things for fun, research, and profit. See my computer page for more details.

Chris Lomont's Graphics Page

Sun, 02 Jun 2019 15:51:40 -0400

Graphics has always been my first love (and then there came chess, music, math, physics, and computers....)

The programs I use most are Real3D and Mathematica, as well as many, many custom pieces of rendering and image processing software. Recently I have written some code that renders the spline outlines of TrueType fonts to make neat animations. I will post the screensaver eventually….

The background here is from a custom OpenGL polyhedron rendering program I wrote for custom animations. Almost every other graphic on this website was created by me.

Chris Lomont's Photos Gallery

Sun, 02 Jun 2019 15:51:40 -0400

Photo galleries - todo - organize and display better, reinstate descriptions

todo - only shows one set for now, make able to start many galleries from one page

People

All camping8

April 27 2003 014

Chris Lomont's Links Page

Sun, 02 Jun 2019 15:48:27 -0400

Super old links page from the 1990s :)

Links

here you'll find some things I use to waste time

I created this page from my Favorites (IE4.0) directory using a small tool I wrote Fav2HTML (C++ source)

Topics: Computer Gaming and Emulation, Programming, Graphics, Math Stuff, Music, Puzzles, Misc

Computer Gaming and Emulation

Arcade Emulation

BETHESDA - Ars Est Celare Artem
Eclipse's Classic Arcade Emulator Page

Baldurs' Gate links

Baldur's Gate Chronicles
Baldur's Gate Dungeon
GAMER'S ARENA - Baldur's Gate Character Editor
Mud Master Beta

Chris Lomont's Professional Page

Sun, 02 Jun 2019 09:36:23 -0400

Here are some documents related to me. Happy hunting.

Resume (HTML , PDF )

Chris Lomont's Online Password Hasher Page

Sat, 01 Jun 2019 22:01:43 -0400

Chris Lomont's Online Password Hasher

August 2006 - Version 0.3

Chris Lomont's Contact Page

Sat, 01 Jun 2019 21:12:03 -0400

My email encoded to help fight spam.

New C# syntax and features

Sat, 01 Jun 2019 17:08:08 -0400

Here’s a brief summary of C# features by version.

30 Algorithms in 60 Minutes

Wed, 15 May 2019 12:56:57 -0400

This is a 60 minute talk in which I tried to cover 30 algorithms and data structures in a concise manner. It covers all sorts of areas: sorting, string searching and matching, backtracking, randomness, skip lists, hashing, bloom filters, graph algorithms, space partitioning, concurrent and immutable data structures, cache oblivious techniques, compression, boolean satisfiability, and control theory.

Computation: Theory, Methods, Limitations, and the Future

Mon, 25 Feb 2019 12:58:12 -0400

These slides are from a talk I gave on many aspects of computing, starting with classical computing (Hilbert’s 10th problem, Church and Turing, Godel, boolean functions, complexity theory, transistors, Moore’s law and demise), then going through physics (relativity, quantum mechanics, quantum field theory), and finally into quantum computing basics (qubits, superposition, entanglement, no cloning, basic gates) and quantum algorithms (Deutsch, Simon, Shor, Grover).

Then I cover advanced quantum topics, such as quantum machines,quantum complexity theory, the Quantum-Church-Turing-Deutsch principle, graph isomorphism, quantum error correction, and quantum security. A final speculative section covers even weirder computation ideas (closed timelike curves, string computing) and how computing seems intertwined with the nature of reality (It from Bit, Simulation Hypthesis, Free Will Theorem).

Intro to Wireless Communications

Sat, 21 Jul 2018 12:59:10 -0400

This talk is an intro to wireless communications, starting with the basic physics of EM waves and how they interact with materials, then how antennas work, then on to antenna properties and design. Next modulation schemes are discussed, showing how data is encoded and transmitted over noisy channels via modulation, spread spectrum, time and frequency division, and other methods. Noise in the form of doppler, intermodulation, and other causes is covered. Information theory (channel capacity, Shannon entropy, error correction) is covered. Finally specific protocols are analyzed under this framework: FM, NTSC, remotes, WiFi, Bluetooth, ZigBee, satellite radio, GPS, and cellular formats.

Cryptography Best Practices 2018

Mon, 02 Apr 2018 12:58:39 -0400

This talk covers cryptography best practices as of April, 2018. Background on each area is covered, with each section ending with a best practices slide. Sections are Symmetric Encryption, Asymmetric Encryption, Key Lengths, Hashing/HMAC, Password usage, Key Exchange, Random number generation, Digital Signatures,

Intro to Functional Programming with F#

Wed, 14 Mar 2018 12:58:59 -0400

This talk is an introduction to functional programming, with a focus on F#. The first section covers functional programming history, techniques, and benefits. The second part shows how this is used in F#, covering F# syntax and some special features like Type Providers, Units of Measure, and performance compared to C#.

The third section goes into mind-bending topics like immutable data structure implementation, currying, the y-combinator, contravariant and covariant functors, and category theory.

Meltdown and Modern CPU Architecture

Wed, 10 Jan 2018 12:56:17 -0400

This talk covers CPU architecture from the early days (Intel 4004) through modern designs (2018, Intel i7 and i9), with a view towards how the Meltdown and Spectre exploits were discovered. It covers virtual memory, process separation, cache issues, RAM details, pipelining and stalls, branch prediction, Moore’s law versus physics, and finally how Meltdown and Spectre are the consequence of many of these design decisions.

In the end I show the code for Meltdown along with a demo.

The Cosmic Distance Ladder

Sun, 19 Nov 2017 12:58:24 -0400

The Cosmic Distance Ladder is how mankind has determined the distances to various astronomical objects, basically by deducing closer “rungs” on the ladder and using them to determine farther distances (higher rungs on the ladder).

These notes are from Terry Tao, modified by me to suit my audience and to add other topics.

Walking Ant Probability Problem

Wed, 01 Nov 2017 17:08:08 -0400

Here’s a math puzzle.

Overview of Cryptology

Mon, 19 Jun 2017 10:49:20 -0400

Here are slides for a long (3-4 hour) talk covering many aspects of cryptology. Topics include simple ciphers, breaking codes, private and public key crypto, block modes, stream ciphers, key exchange, random number generation, modern crypto design, hashing, password security, breaking (differential, higher order, many more..), out of band attacks (timing, cache, power, hardware, …), homorphic encryption, quantum protocols, and more….

A Universal FRACTRAN Interpreter in FRACTRAN

Mon, 01 May 2017 17:08:08 -0400

Here’s FRACTRAN, a weird fraction based programming language, written in FRACTRAN.

Generating Uniform Random Numbers on [0,1]

Sun, 05 Mar 2017 17:08:08 -0400

How does one generate uniform random numbers in [0,1] using IEEE 754 floating point formats? It’s tricky.

Efficient divisibility testing

Tue, 21 Feb 2017 17:08:08 -0400

Here’s bit tricks for efficient divisibility testing.

Making Three NOT Gates from Two

Sat, 17 Sep 2016 17:08:08 -0400

This is a hard puzzle about using two NOT gates to build three.

Compression Notes

Mon, 29 Aug 2016 17:08:08 -0400

Here’s some notes on compression.

LZCL: An embedded compression library

Mon, 29 Aug 2016 17:08:08 -0400

Here’s an embedded compression format I designed to meet certain requirements. It’s small, fast, and efficient.

Average segment length

Tue, 23 Aug 2016 17:08:08 -0400

What’s the average length of a segment chosen uniformly by area on a unit square?

How many prisoners?

Tue, 23 Aug 2016 17:08:08 -0400

This is a nicely hard problem in the common prisoners and warden format.

Pick a Number

Tue, 23 Aug 2016 17:08:08 -0400

Here’s a result that is completely non-intuitive.

Test site features

Fri, 01 Jul 2016 17:08:08 -0400

A post to test site features such as tables, math, code…

Mon, 01 Jan 0001 00:00:00 +0000

Color Conversions

This is a quick note for converting byte values colors in 0-255 back and forth to floating-point colors in 0-1.

The Problem

A common (yet incorrect) method (shown in C++) looks like this:

#include <cstdint> // uint8_t

// byte color in 0-255 to 32-bit float in 0-1
float ColorU8ToF32_BAD(uint8_t colorB)
{
    return colorB/255.0f;
}

uint8_t ColorF32ToU8_BAD(float colorF)
{
    return (uint8_t)(colorF*255.0f+0.5f);    
}

This suffers from significant bias away from the end colors 0 and 255, and the +0.5f “trick” to round values does not always work, which can bite you. Some problems with this style of conversion: