A really simple program that uses SDL library to simulate cannonballs being fired and colliding and bouncing off of each other.
I used it to test the waters on using SDL for graphics, and collisions. Putting it on GitHub so that I may easily reference it later.
There are a few branches of this that use different programming languages.
This program has been released in the Public Domain meaning you can use it however you wish, read the license file here or you can read here for information of the Unlicense in general.
-
First and foremost, this code is "AS IS", meaning we cannot be sued if it doesn't work
-
You can modify this code any way you wish without credit (but we would certainty appreciate it)
-
You can any/all of this code for private and/or commercial use
In order to run the program properly you will need to download SDL2-2.0.3 or higher AND SDL2-image (these are two different libraries).
A link for SDL2 can be found here.
A link for SDL2 image can be found here .
You will want to download the Runtime Binaries (if you have windows I recommend 32 bit over 64 bit; even if you have a 64 bit computer).
When all is said and done you should have the following files in your folder. (Also note that you should be able to put the dll files in your C drive).
FolderName\
FolderName\Physics-Simulation.exe
FolderName\SDL2.dll
FolderName\SDL2_image.dll
If you are using the version I compile, which can be found in the release tab you will also need the following binaries.
FolderName\libgcc_s_dw2-1.dll
FolderName\libstdc++-6.dll
They should be included in the release.
Let me know if I am missing a dependences that I might have forgotten about due to my own system set up.
The first time you run the program a "Config.ini" will be created it should look something like below:
Config File for the Cannon.exe
1.4.0-R
Screen Width: 640
Screen Height: 480
Log Ball's path: 0
Enable Drag Mode (experimental): 0
Draw Ball path on screen: 0
Collision Method: 1
Number of points to track: 5
Delay between recording points: 25
You can use this to change things like the screen height and width, and other stuff.
"Log Ball's Path" (if enabled with a 1 instead of 0), will cause a a file called "logfile.log", which will contain the placement of every ball on every update (it gets quite big as you can guess).
"Enable drag Mode" (if enabled with a 1 instead of 0), will cause the cannonballs to be effected by drag. It is listed as experimental because I based the equations used off of several things I found online and I cannot verify how accurate it is.
"Draw Ball path on Screen" (if enabled with a 1 instead of 0), will cause small pixels to trail after each ball.
"Collision Method" you can change how the balls will interact with each other when they collide based on the number in the table below.
| Name | Number | Explanation |
|---|---|---|
| CollideElastic | 0 | This is normal collision in a perfect world without friction, they hit and bounce off, no energy is lost. |
| CollideInelastic | 1 | This is the real life situation. Balls collide and, bounce off of each other losing some energy. |
| CollidePerfectInelastic | 2 | In this method the balls collide and then stick together. |
| CollideNone | 3 | The balls do not collide and pass through each other. |
"Number of points to track" is the number of past points that will be kept track of if "Draw Ball Path on screen" is enabled.
"Delay between recording points" is the delay (in ticks) between everytime it records a point, if "Draw Ball Path on screen" is enabled. A smaller number means that the points are recorded much faster.
Once you start the program you will be greeted with a beautiful black screen. To create a new cannonball you click (and hold down the button) you can now move your move around to change the angle that the new cannonball will be fired at; as well as the longer the line the faster it will go. When you are happy with the angle and speed simply release the mouse button and it will be created at the point where you clicked the mouse button down.
The longer you hold down the mouse button the larger the radius of the ball will be and as a result, the more mass the ball will have. You can get an idea of how much mass a ball has based on how transparent it is, the more transparent it is the lighter its mass.
You can also press the following keys to yield effects
K = All Balls will be "killed".
R = All motion will be stopped.
Q / ESC = Program will exit.
F = Every so often a randomly generated cannonball will be created
T = Toggle toolbox on/off
P = Toggle pause for the simulation
Right Arrow = Select next tool
Left Arrow = Select previous tool
1 = Select Fire tool
2 = Select Drop tool
3 = Select Rope tool - DISABLED ATM
4 = Select Delete tool
5 = Select Drag tool
6 = Select Info tool
Clicking a dragging on screen will cause a white line to drawn from original click location to current mouse condition.
When mouse is released a ball will be fired in the direction from the first click location to where released. The ball's velocity will be proportional to the distance between the two points.
The mass of the ball will be proportional to the length of time that the mouse was held down for.
Clicking on the screen will cause a ball to be created at selected location. The ball will have no velocity and its mass will be proportional to the length of time the mouse is held down for.
Clicking on a ball will cause it to be attached to one end of a rope. The rope can then be attached to another ball, or pinned to background.
Clicking on a ball will delete it.
Clicking and dragging on a ball will allow you to move a ball where the mouse is. When released the ball will still have its inital velocity.
Clicking on a ball will write information about it to the console