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!
Month: January 2012
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…