Week 2 Progress

Overview

This week, we made a lot of progress on the project. We are ahead of schedule to meet our goal of finishing within the ten week term. We've already made a few changes and are all excited about where the app is headed.

Major Changes

We've decided to change our game idea from having levels to being more of a creative/sandbox-mode sort of game. Players will be able to place planets, suns, asteroids, or any other solar bodies they want to make wherever they want in the virtual environment. They will be able to adjust their sizes, velocities, and positions relative to the other bodies on the screen. We are still trying to decide if we still want to incorporate some kind of game aspect or just make it a simulation. Making it a simulation would be cool because it would give the “game” more educational value. It would make more sense then to incorporate stats and numbers (like a body’s mass, velocity, and distance from other bodies) in a table. This would really help make it educational but it wouldn’t make a lot of sense to include it in a game.

If we were going to make it a game, however, it would need to have some kind of points system where players could get high scores. One idea we have is for a player’s score to be based on the number of bodies they can put on the screen without them colliding. This will become more difficult as they add more bodies because all of them will have gravitational forces acting between them. There would be a lot of strategy involved in deciding which moons should orbit which planets and which planets should orbit which suns. If we did go this route, we’d need to set boundaries in space and also other constraints to make the game more fun.

Progress

We made a lot of progress this week in the programming of the game. Much of this can be seen in the smaller posts we made over the last few days. As of right now, we have a working physics-based simulation running on Android and PC. Right now there are only three bodies in space but the code is set up so that it’s easy to add more. The gravity and physics is realistic and uses the real formulas for gravity and centripetal force. A user can launch the bodies around the screen and change the mass/size of one of them. We’re calling this one the test planet right now because we’re testing all of the future functionality on this one body before we extend it to work on all of them. On the desktop version, you can press the “O” key to make the test planet orbit the sun. You can use the arrow keys to zoom out and in and you can click and drag to pan the camera around.

Future Plans

We’re going to set it up so that there is a set of control buttons that slide out of the side of the screen where people can choose whether they want to be in view mode or edit mode. In view mode they will be able to pan and zoom the camera without worrying about editing the bodies. In edit mode, they will be able to select certain planets to edit by clicking on them. They can click and drag to launch them or click and then scroll the mouse wheel to change their sizes. There will also be an orbit button on the screen. All of this functionality will work similarly on the phone. People will be able pinch their fingers in and out on the screen instead of scrolling the mouse wheel to zoom and change planets’ sizes. All of the key commands will be replaced with onscreen buttons. (see picture below)

Here is a basic concept of the menu we plan to implement into the app. The "+" button is used to add a new body to the simulation. The view button is used to get to settings to adjust zoom and pan the camera. The settings button is for adjusting the properties of a specific planet. When a body is selected, a user will be able to use the buttons to pick an orbit, see info about it (see the stats in top left), and delete the body entirely. They will also be able to launch the body (change its velocity) by dragging back on it or adjust its size by scrolling or pinching the screen.

Challenges

One of the biggest challenges we’ve faced so far is scale. Because gravity is such a weak force and space is so spread out, we’re having a hard time fitting everything in a reasonable amount of space. We solved this mainly by making the gravitational constant equal 1 in the formula in the code. The real value is 6.674×10⁻¹¹ N⋅m²/kg² so this is obviously a major adjustment. We will account for this by scaling the radius and masses that we display on the screen. Instead of being 200 meters like it actually is in the game, it might be scaled to 200×10⁹ meters. Another problem is that libGDX has a maximum velocity of 2 units/frame. This is why we can’t set a realistic scale because at 60 frames per second that would mean a maximum velocity of 120m/s. That would be much slower than actual planetary motion and it would literally take years for a body to move across the screen. You also wouldn’t be able to see any acceleration due to gravity if the velocity was already at the maximum. This wouldn’t be good for the educational factor in the app. We’ve been working on solving this by, in addition to scaling G, adding a scaling factor for all of the numbers in our code. We all worked together to figure out the math behind this scaling because different numbers (e.g. distance and mass) need to be scaled differently. It seems to be working pretty well right now but we’ll see what other kinds of changes need to be made in the future.

Team Roles

Since Nick has the most experience with Java and Android development, he has been doing most of the actual programming so far. Ebed and Jiho have been watching Java lectures online to get up to speed. They are also working on graphics and helping to solve problems and plan for the future.