Variance Shadow Map

Variance Shadow Maps use a floating point texture to hold the values of the mean and mean squared distance from light source to shadowed pixel. The original paper published by William Donnelly and Andrew Lauritzen can be found here on the Variance Shadow Map page.

This technique is great because it allows the graphics hardware to be used to blur the shadow map and produce soft shadows. My first attempt at this routine doesn't use any filtering but this means it can be compared with the previous standard shadow map demo. The screenshot shows a single case where the standard shadow map had a banded shadow, and where the Variance Shadow Map has an artefact free shadow.

Shadow maps

No percentage closer filtering or bias as used in the yacht demo. Just a simple 512 square shadow map and sharp edged shadows. I have programmed this simple shadow map algorithm so I can make comparisons with other shadowing routines.

Blend shapes

I've added something in the middle of the test level that looks like a reshaping biscuit. This is a blend shape, blending between cube, sphere and pyramid. This can be used for deformable objects.

Picking algorithm

The current "tech" demo demonstrates a picking algorithm which lets the user control the placement of objects through the mouse pointer. A ray cast is used from the eye to determine both the object for selection, and the drop point. The picking logic determines the best position to place on the drop point. This takes some getting used to, but the speed which objects can be positioned shows it's effectiveness.

Struffy

A "tech" demo has been added to the downloads section. This is a small showcase of Struffy, my abstracted cross platform engine. This engine has been in development for 5 years.

The demo renders some physics objects which are modelled using ODE, although the physics implementation is also abstracted. The objects can be selected and moved. I'm going to continue to add new Struffy demos to this blog. The older versions of the same demo remain on the site but have been removed from the downloads list to save bandwidth.

WeatherLink to APRS

I've added a link in downloads describing an approach to uploading data from a weather station program to APRS using the scripting language PHP.

Here, the weather station program is WeatherLink and the APRS program is UI-View32, but this approach could be applied to other Weather stations and other APRS programs.

APRS was devised by Bob Bruninga, call sign WB4APR. The acronym stands for Automatic Packet Reporting System. Ham radio enthusiasts use this system across radio waves.

Through it's widespread adoption, a large network of stations running APRS has grown. The APRS network is currently used to place objects of interest on real world maps. This information is often details of the Ham enthusiast themselves, but equally it can be information that's useful to the Ham community. For example, hospitals, roads, ports and here, weather stations.

Nintendo Wii

After seeing Johnny Chung Lee's Wii remote projects I wanted to try them, but I had given my parents my Nintendo Wii. Instead, I made my own sensor bar and borrowed a Wii remote for work. You can use the Mugi easy LED unit guide if you fancy making one. IR Leds are invisible to the naked eye so you can use a phone camera or visible LED to establish if your circuit is working.

I've implemented my own HID driver in C++ from the WiiLi pages, but the library referenced from his site is worth downloading.