Wednesday, July 23, 2008

Radiohead "House of Cards" Surface Fit

As you may know, Radiohead graciously released some of the 3D data from their "House of Cards" video on Google Code. Each frame of the data has approximately 6000 points of x,y,z position data, as well as a colour intensity value (like it's in black and white), spaced non-uniformly through the space.
I've been using some Radial Basis Function Networks to approximate some functions and wanted to see how they worked to interpolate the non-uniform data only a uniform grid. Using a Thin Plate Spline basis function, I created the surface in the image. A thin plate spline is a surface that fits exactly on the control points and the surface between the control points bends as if it was a thin plate of metal. There is also, luckily, a closed form solution for the parameters.
If you're interested, the Matlab code is available of the Matlab Central File Exchange.
Next: video.

Tuesday, July 22, 2008

Forest Reverb Model

For your auditory pleasure, Travis Wiens and Nutaksas Research are pleased to announce the release of a Forest Reverberation Modeller. This package of Matlab functions allows you to simulate the impulse response of an arbitrary forest of any number of trees of any size at any location, as well as source and listener lcoations.
Based on Morse's theory, each tree is treated as an acoustically hard cylinder and the effect of each path from source to receiver via any number of trees is calculated. The maximum number of scatterings may be limited to cut down on excessive calculation times.
The idea was based on Kyle Spratt's Treeverb proposal, although it was developed independently and gives different results.
Download the code from Matlab Central File Exchange, and feel free to check out the other files available. Watch this space for a more technical description.