Advanced Graphics HW #3
Dane Larsen

Depends on: libsfml-dev and qmake

Relevant links: GLSL Warping demo based on this: http://www.iquilezles.org/www/articles/warp/warp.htm
                Perlin/Simplex noise courtesy of https://github.com/ashima/webgl-noise

Controls:
	Click and drag to rotate the scene
	Mouse wheel zooms
	'ESC' - quit
	'C' - go forward one texture shader
	'X' - go back one texture shader
	'G' - toggle god-rays
	'E' - toggle equirectangular warping
	'W' - toggle horizontal texture wrapping
	'Z' - if the current shader is the "earth" shader, toggle warping on that shader
	'S' - view the texture being applied to the sphere
	'P' - toggle the planet
	'L' - toggle the visibility of the external light (only has effect when god-rays are off)
	
The "earth" shader is used to demonstrate the effects of warping 
(used in all the texture shaders except the gray one).

The "plain gray cloudy" shader is a visualization of the 
Fractional Brownian Motion used to warp the textures. 
It's also used as a base for the more abstract textures.

Toggling equirectangular warping and horizontal wrapping will 
affect the texture displayed with the key "S". This is used to 
demonstrate how to wrap a rectangular texture around a sphere.

I tried to apply the god-rays shader to the external light 
that is visible when god-rays are off. Unfortunately that 
shader needs work. It applies to everything in the scene, so 
anything that was lighter than the background (everything) 
was being smeared, and it looked... weird. Also, I'm not 
calculating the position of the light source correctly in 
the vertex shader. It works fine if the source of the rays 
is at (0, 0, 0), but anywhere else produces strange results.

The god-rays shader might make an (improved) appearance in later
assignments, but I don't have time to fix it right now.