Gaseous Giganticus

This program is used to create procedurally generated gas giant planet cubemap textures for the game Space Nerds In Space.

Sample Output

The output of gaseous-giganticus consists of six square images that can be used as a cubemap to texture a sphere. Here the output is viewed with "mesh_viewer", from the space-nerds-in-space repository.

Getting Started

1. clone the project
2. Type "make"
3. run "./gaseous-giganticus --help" and do what it says.
4. See also: output of "nroff -man < gaseous-giganticus.1 | more"

The program requires one PNG input image, which should ideally be about 200 pixels wide and about 1200 pixels tall, and blurred. It outputs 6 square images that can be thought of as the faces of a cube, which you can imagine being overinflated until it is a sphere. The layout of those six output images is as follows:

        +------+
        |  4   |
        |      |
        +------+------+------+------+
        |  0   |  1   |  2   |  3   |
        |      |      |      |      |
        +------+------+------+------+
        |  5   |
        |      |
        +------+

If you wish to watch the progress of the program while it works, you'll need to compile and run "mesh_viewer", which is part of Space Nerds In Space.

Here is a video demoing the gaseous-giganticus and mesh_viewer. This video is a bit old, and I should probably make a new one, but it will have to suffice for now.

Prerequisites

1. libpng

Coding style

1. Run "git diff | ./checkpatch.pl -". It will tell you what you did wrong.

TLDR: Tabs, not spaces, snake_case, not CamelCase.

Contributing

To gain an understanding of how the program works, see this slideshow. Use arrow keys to navigate. That slideshow does not work well on mobile, so find a real computer.

If you're looking for a challenge, it would be really cool to do a more proper fluid simulation. This could probably be done by advecting the velocity field and then eliminating divergence from it, something like what is described here, except done on the surface of a sphere instead of on a plane. The velocity field is contained in the vf structure. Some framework code is already in place, we "just" need to implement the body of the functions advect_velocity_field() and remove_divergences().

Please read CONTRIBUTING.md

Authors

• Stephen M. Cameron
• Tobias Simon (initial author of quaternion library)
• Jeremy Van Grinsven (many additions to quaternion library)

License

GNU GPL v. 2

Notes

On Sunday, October 21, 2018, this code was split off from the Space Nerds In Space repository at https://github.com/smcameron/space-nerds-in-space where the code was originally developed.

An effort was made to preserve the history (git log, etc), and this effort was 99.9% successful, but there are a few small differences from the original history. Most significantly, the Makefile does not exist for most of the history in this repository because the Makefile used in Space Nerds In Space would have been broken anyway and would have contained tons of irrelevant cruft. The Makefile in this repository was added only after the entire gaseous-giganticus history was imported. Less significantly, a few commits were made out-of-order, and although the original dates were preserved in the log, checking out a particular sha you may find some small differences if you compare with what was in the Space Nerds In Space repository at a corresponding time. At the time the Makefile was added to this repository, all source files present here were identical to those also present in the Space Nerds In Space repository, meaning those small differences were resolved eventually.