AI Steering

For many games, AI entites need to move around in a somewhat lifelike manner, or at the very least a consistent manner. The final decision as to which direction to move in can be quite complicated due to a number of competing factors, for example: Pathfinding waypoints, points of interest or obstacles. A common way to reduce the complexity of the decision is to separate the decision into several steering behaviors. Steering Behaviors Craig Reynolds introduced a paper at GDC 1999 to deal with what he described as the middle level…

Frame Rate Independent Damping using Lerp

A quick aside for those not familiar with Unity: Each script has three different update functions that can be called. Update is called as you would expect, and LateUpdate is a version that’s called well, later on in the frame. Both of these should use the global (yikes) Time.deltaTime to access the variable frame time. FixedUpdate uses Time.fixedTimeDelta and runs on a fixed timestep, so can potentially run multiple times per frame. The Great Lerping Problem It seems to crop up on the Unity forums again and again and again…

Physically-Based Shading

I’ve noticed the term ‘physically-based shading’, or variants thereof, used with increasing frequency these days. I’m happy about this, since it represents a movement away from hacking around with magic numbers and formulae in shaders, towards focusing on the underlying material and lighting models. It offers consistency, predictability and constraints where previously these had been somewhat lacking. There was a great course at Siggraph this year purely about physically based shading. The trouble is, I’m still not really sure exactly what it means… Energy Conservation When looking at material response,…

Derivative Map Artifacts

I had been suffering from some strange artifacts on the edges of my objects when using derivative maps. After much time spent in GPU Perf Studio, I finally realised that my mipmap generation was not correct. It was introducing one extra column of garbage at every level. My use of FXAA and anisotropic filtering was just making the problem more evident. I would recommend using regular trilinear filtering for derivative maps anyway. So, mea culpa and all that. Let the name of Morten Mikkelsen and derivative maps be cleared!

Derivative Maps vs Normal Maps

This post is a quick follow up to my previous post on derivative maps. This time I’m going to compare the quality and performance of derivative maps with the currently accepted technique, normal maps. I’ll be using the precomputed derivative maps for comparison since the ddx/ddy technique just isn’t acceptable in terms of quality. Quality Here’s the close up shot of the sphere with the moon texture again. This shows the derivative map implementation, and if you mouse over, you’ll see the normal map version. There are some slight differences…

Cubemap Texel Solid Angle

Warning: This post is going to be pretty math heavy. If you suck at math, then go and read this first, then come back. If you still think that you suck, then I suggest going to Khan Academy and start watching videos. You won’t regret it! I was reading through the AMD CubeMapGen source last week and came across the code for calculating the solid angle of a cube map texel. This code piqued my interest, since it seemed very terse for what I thought would be a horrific calculation….

Derivative Maps

I recently came across an interesting paper, Bump Mapping Unparametrized Surfaces on the GPU by Morten Mikkelsen of Naughty Dog. This paper describes an alternative method to normal mapping, closely related to bump mapping. The alluring prospect of this technique is that it doesn’t require that a tangent space be defined. Mikkelsen is apparently well-versed in academic obfuscation (tsk!), so the paper itself can be a little hard to read. If you’re interested in reading it, then I would recommend first reading Jim Blinn’s original bump mapping paper to understand…

UI Anti-Aliasing

I’ve been working on making a really simple IMGUI implementation for my engine at home. I like to do a little bit of research when I’m approaching something new to me like this, so I went hunting around for publicly available implementations. While doing this, I came across Mikko Mononen’s implementation in Recast. I was impressed when I ran the demo with how smooth his UI looked. It turns out that he’s using a little trick (which I’d never seen before, but I’m sure is old to many) to smooth…

Visual Studio Addins Updated

DoItNow & RevisionItNow I’ve updated the Google Code repository for DoItNow with a newer version. I’ve removed all source control features from DoItNow and separated them into their own add-in. This should make it more compatible with other add-ins you may be using to handle source control. I’ve uploaded the Mercurial version of the add-in, but the full source is available should you want to change it back to Perforce. I’m only using Visual Studio 2010 at home now, so the project files are all in that format at the…

MockItNow: Now with Win64 goodness!

A couple of fine chaps named Julian Adams and Clement Dagneau from my previous company Black Rock Studios (née Climax Racing) took it upon themselves to tackle the daunting task of  porting MockItNow to x64 (MSVC). They’ve kindly shared their efforts back with the main repository in google code. Feel free to profit from their hard work! Thanks a lot Julian & Clement!