Raymarching an Infinite City

1. Alice Yang CIS 565 Final Project Raymarching an Infinite City

2. Ray Marching/Sphere Tracing • Starting from eye, proceed in small steps along ray. • Distance Estimator tells you how close you are to object. • When you are close to a certain threshold, stop. • Coloring by number of steps taken gives us cheap AO with no need for lights. Source: http://blog.hvidtfeldts.net/index.php/2011/06/distance-estimated-3d-fractals-part-i/

3. Framework • The entire project is contained in a fragment shader written in GLSL • Code can be viewed and run on GLSL Sandbox (http://glsl.heroku.com/e#2306.2) • Project built off of Paulo Falcao’s basic raymarch framework, extended to support a number of additional features

4. Domain Repetition Source: http://www.iquilezles.org/www/articles/distfunctions/distfunctions.htm /

6. Building Variation • Find “seed” constant for every building as input into random float generator • vec2 pos = vec2(ceil(p.x/c.x), ceil(p.z/c.z));

8. Building Geometry • Union operation: Add roofs and attics to tops of buildings • Subtraction operation: Windows and wall indents

9. Building Geometry: Windows • Create 2D cross and repeatedly subtract from building bodies • Insert inner structure to prevent building from looking hollow • “free” variation from random heights applied afterwards Source: http://www.iquilezles.org/www/articles/menger/menger.htm /

11. Textures • Mostly flat colors since project focuses on geometry • Half of the city samples from procedural brick texture.

12. Constant values for brick and mortar color as well as brick size and brick percentage • After position is calculated, every other row is offset by half a brick’s width • Step function: If the fract(position) is less than brick percentage, use brick color. Otherwise use mortar color

15. Live Demo • http://glsl.heroku.com/e#2306.2