Geomap Demo

Download (7.5Mb)

Installation

Included with the program is the Microsoft XNA 3.1 redistributable. This MUST be installed in order for the demo to run.

1. Unzip the contents of this file into the directory of your choosing
2. Run xnafx31_redist.msi (XNA 3.1 Redistributable, included in download)
3. Ensure that your DirectX is up to date via Windows Update. DirectX 9.0c redistributable may be required as well if you don't have it already (if you've installed a game in the last few years, you probably have it).
4. Run Kingdom\Kingdom.exe to run the demo

Requirements

1. A video card supporting Shader 2.0 (pretty much any video card in the past 5 years)
2. XNA 3.1 Redistributable
3. DirectX 9.0c Redistributable

XNA 3.1 Redistributable Information

The Demo

This executbale loads a geodesic grid containing 642 cells. 12 of these are pentagons while the rest are hexagons. The grid is derived from a subdivided icosahedron. While I am able to generate grids of arbitrary size, that's not demonstrated here (grid is built as an XNA Content Pipeline project, not at run time)

Controls

A simple first person camera is implemented. Use the keyboard arrow keys and right mouse button to move the camera. Shift + up/down will move the camera vertically.
Left clicking tiles on the map will increment their texture page.

Notes

Thanks for checking out the demo. Feel free to contact me either on Facebook or at levi.baker.101@gmail.com
I'll start putting together a roadmap for future development soon.

Geodesic Map - 1 - Generating a geogrid.

So I wanted to tinker with a hex grid. I had a few ideas, but nothing really took hold until the thought of projecting the hex grid around a sphere occured. Was such a thing possible? Yes, sort of. How would the mesh be generated? With lots of work. Could it be done dynamically to allow for multiple map sizes? Yup.

The Process

Generate Icosahedron

A sphere made purely of hexagons isn't quite possible, or if it is, I couldn't find any confirming documentation. Using an icosahedron will yield 12 5-sided cells across the surface of the grid, each one being at the original icosahedron's vertices (also known as a dodecahedron).

All images curtesy of the wonderfully informative BUGS project.

1. The base icosahedron
2. Each face subdivided
3. Project each new vertex out to the unit sphere
4. This process can be repeated until you reach the total number of cells you wish

Generate Cells

Once you have reached your target cell count, it's time actually generate the cell mesh. The basic process runs as such:

1. Foreach vertex in the subdivided icosahedron:
   
   1. Find all neighbor cells
   2. Foreach neighbor cell:
      
      Find the midpoint of neighbor cell and neighbor + 1 cell, this forms one section of the hexagon (or pentagon)
      
      
   
   

Example Subdivision Levels

Level 1 - 42 Cells Truncated Icosahedron aka, soccer ball, buckyball	Level 2 - 162 Cells	Level 3 - 642 Cells

Notes

Some of the hexagons will be warped slightly due to wrapping to a sphere and floating point errors.

Links

Icosahedral Hexagonal Grids

• Platonic Solids
• http://en.wikipedia.org/wiki/Geodesic_grid
• http://blog.earthbrowser.com/2007/02/global-grid-icosahedral-hexagonal-grid.html
• http://webpages.sou.edu/~sahrk/dgg/
• http://kiwi.atmos.colostate.edu/BUGS/
• http://kiwi.atmos.colostate.edu/BUGS/geodesic/text.html