Logarithmic Spiral Distance Field

I have been playing around with distance field rendering, inspired by some of Iñigo Quílez’s work. Along the way I needed to define analytic distance functions for a number of fairly esoteric geometric primitives, among them the logarithmic spiral:
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Conway’s Game of Life in GLSL/Pyglet

Conway's Game of LifeAs a followup to yesterday’s GLSL wrapper class, here is a small example of the class in use. This is an implementation of Conway’s Game of Life, running entirely on the GPU. The picture here really fails to do the game justice, as you need to see it in motion, so if you can’t run the program, drop over to YouTube for a blurry demonstration.

You will of course need to grab a copy of yesterday’s shader class, and drop it in the same directory before running this example. When the example loads you will be presented with a blank screen – resize the window by dragging the lower-right corner, and patterns will appear.

This example runs 3 simulations simultaneously, one in each of the red, green and blue colour components. Rather than setting up an initial state, it uses the garbage present in the back buffer to seed the simulation – this works fine on Mac and Windows, filling with garbage when you resize, but may not work as well with other platforms which are over-zealous about clearing memory. Also note the the simulation wraps around from top to bottom and from side to side, allowing patterns to propagate cleanly across the edges.

Although the implementation is my own, the concept of running the Game of Life with GLSL is something I have seen elsewhere. I don’t recall where, but if anyone can remind me, I would like to give credit where it is due.

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Constructing a Billboard Matrix

Billboards are an important part of 3D graphics, especially for use as user interface elements. Unfortunately, detailed information on how to construct them is a little hard to find, so I have derived the billboard matrix from scratch. In case anyone else is looking for this information, the derivation is as follows: Continue reading