Welcome to Reanimator Ltd
Reanimator Ltd specializes in hardcore programming and maths.
This website contains articles and code related to these subjects. I hope you find the articles interesting, and maybe even useful!
Pixel-perfect Derivatives on GPU
Quick maths hack to get the correct per-pixel derivative of any value that is linear in worldspace.
Hacking Timewarp to Fix Blurry Rotation in VR Games
Timewarp is almost designed to do this
Finding the Nth Root
This article describes how to quickly find the Nth root using basic arithmetic operations and floating-point bit-twiddling hacks.
Thoughts on Deep Neural Networks
These are some thoughts I had last night while staying up far too late thinking about this!
NP vs co-NP
co-NP and NP morally use the same resources (including time) on non-deterministic Turing machines, but you need a metasystem to do it.
Why are Scrolling Messages Always in Italics?
The characters on 5x7 LED displays look upright when stationary, but slanted (italic) when moving. Why is that?
A Novel Raytracing Algorithm for GPU
I present a novel acceleration structure and raytracing algorithm which explicitly leverages the capabilities of the GPU and avoids the "up and down the tree" nature of kd-tree raytracers.
Finding the Exact Pseudoinverse
You're going to use full-blown SVD just to get the pseudoinverse? Really?
Matrix Decomposition for Dummies
How do all these matrix decompositions work, and how do you code them?
The Derivative of a Procedure
Some pretty out-there stuff about procedures having derivatives ...
When Is This Expression True?
When is this expression true for random variables A, B and C?
p(A|C) = p(A|B)p(B|C) + p(A|!B)p(!B|C)
Monads in C++
Monads have a deep mystery surrounding them, but they're actually a very simple concept. There is nothing magic here - as a C++ programmer you've probably already done this yourself, or at least seen it done, but probably in a different context. Read more for my explanation of monads for C++ programmers.
How to Isolate a Non-Deterministic Bug in Version Control
An Adventure in Bayesian Inference
This article explores the question of how best to isolate a bug in version control using binary chop, when the bug doesn't always manifest. I derive a probabilistic algorithm to solve this "Bayesian Binary Search" problem, from first principles.
The Myth of the "Unrealizable" Filter
DSP textbooks will tell you that a filter graph containing a delay-free loop is "unrealizable". I demonstrate that "unrealizable" doesn't mean you can't code it.
Update 7th Mar 2012: added a worked example.
Operators as Matrices
Should programming languages allow "naked operators" as objects?
SIMD Optimization of IIR Filters
IIR filters seem impossible to convert to SIMD code, since they have a tight loop containing an immediate dependency. This article will show you that it's not impossible, given the right maths.