Project 4: Shape Grammar

For this assignment you'll be building directly off of Project 3. To make things easier to keep track of, please fork and clone this repository https://github.com/CIS700-Procedural-Graphics/Project4-Shape-Grammar and copy your Project 3 code to start.

Goal: to model an urban environment using a shape grammar.

Note: We’re well aware that a nice-looking procedural city is a lot of work for a single week. Focus on designing a nice building grammar. The city layout strategies outlined in class (the extended l-systems) are complex and not expected. We will be satisfied with something reasonably simple, just not a uniform grid!

Symbol Node (5 points)

Modify your symbol node class to include attributes necessary for rendering, such as

  • Associated geometry instance
  • Position
  • Scale
  • Anything else you may need

Grammar design (55 points)

  • Design at least five shape grammar rules for producing procedural buildings. Your buildings should vary in geometry and decorative features (beyond just differently-scaled cubes!). At least some of your rules should create child geometry that is in some way dependent on its parent’s state. (20 points)
    • Eg. A building may be subdivided along the x, y, or z axis into two smaller buildings
    • Some of your rules must be designed to use some property about its location. (10 points)
    • Your grammar should have some element of variation so your buildings are non-deterministic. Eg. your buildings sometimes subdivide along the x axis, and sometimes the y. (10 points)
  • Write a renderer that will interpret the results of your shape grammar parser and adds the appropriate geometry to your scene for each symbol in your set. (10 points)

Create a city (30 points)

  • Add a ground plane or some other base terrain to your scene (0 points, come on now)
  • Using any strategy you’d like, procedurally generate features that demarcate your city into different areas in an interesting and plausible way (Just a uniform grid is neither interesting nor plausible). (20 points)
    • Suggestions: roads, rivers, lakes, parks, high-population density
    • Note, these features don’t have to be directly visible, like high-population density, but they should somehow be visible in the appearance or arrangement of your buildings. Eg. High population density is more likely to generate taller buildings
  • Generate buildings throughout your city, using information about your city’s features. Color your buildings with a method that uses some aspect of its state. Eg. Color buildings by height, by population density, by number of rules used to generate it. (5 points)
  • Document your grammar rules and general approach in the readme. (5 points)
  • ???
  • Profit.

Make it interesting (10)

Experiment! Make your city a work of art.

Warnings:

You can very easily blow up three.js with this assignment. With a very simple grammar, our medium quality machine was able to handle 100 buildings with 6 generations each, but be careful if you’re doing this all CPU-side.

Suggestions for the overachievers:

Go for a very high level of decorative detail! Place buildings with a strategy such that buildings have doors and windows that are always accessible. Generate buildings with coherent interiors If dividing your city into lots, generate odd-shaped lots and create building meshes that match their shape ie. rather than working with cubes, extrude upwards from the building footprints you find to generate a starting mesh to subdivide rather than starting with platonic geometry.