Particle Based Physics Engine in Golang
Physix.go
Introduction
Physix.go is a simple, easy-to-use, and fast physics engine written in GoLang. It provides functions to perform physics calculations efficiently, including particle-based physics simulations.
Features
- Vector Calculations
- Physics Calculations
- Spring Dynamics
- Easy to use with Ebiten.go
Getting Started
Prerequisites
- GoLang must be installed.
- Ebiten must be installed.
Installation
To start, clone this project:
git clone https://github.com/rudransh61/Physix.go
Or install it using go get:
go get github.com/rudransh61/Physix.go
Then run the example files from the ./examples folder. For example:
go run ./examples/ex4.go # which is a simple circular motion
Documentation
Vectors
Vectors are a datatype to store vectors. Import the following file to use vectors:
package main import ( //...other imports "github.com/rudransh61/Physix-go/pkg/vector" )
To make a vector
var MyVector = vector.Vector{X: 30, Y: 20} // X is the x component and Y is the y component of the Vector
Using Function
var NewVec = vector.NewVector(x, y)
Add Vector
var NewVector = Vec1.Add(Vec2)
Subtract Vector
var NewVector = Vec1.Sub(Vec2)
Inner Product of 2 Vectors
var DotProduct = Vec1.InnerProduct(Vec2)
Scale a Vector by a scalar
var ScaledVector = Vec1.Scale(num)
Magnitude of a Vector
var Magnitude = Vec1.Magnitude()
Normalize a Vector
var NormalizeVector = Vec1.Normalize()
Distance between Heads of 2 Vectors
var distance = vector.Distance(Vec1, Vec2)
Perpendicular Vector of a given Vector
var Orthogonal_Vector = vector.Orthogonal(Vec1)
RigidBody
To create an instance of RigidBody, you need to provide all the required fields. First, import these files:
import ( "github.com/rudransh61/Physix-go/dynamics/physics" "github.com/rudransh61/Physix-go/pkg/rigidbody" )
Example:
ball = &rigidbody.RigidBody{ Position: vector.Vector{X: 400, Y: 100}, Velocity: vector.Vector{X: 0, Y: 2}, Mass: 1, Force: vector.Vector{X: 0, Y: 5}, IsMovable: true, Shape: "Circle", // Example shape Radius: 10, // Required for Circle }
To update the position of a RigidBody, use ApplyForce in a loop:
for i := 0; i < 100; i++ { physix.ApplyForce(ball, vector.Vector{X: 10, Y: 0}, dt) // Apply force // .. other code }
To access or change the Force, Velocity, Position:
ball.Velocity // Get the velocity of the ball as a vector.Vector ball.Position.X += 5 // Increase the position of the ball in X direction by 5
Collision Detection
There are two types of collision systems for different shapes:
- Rectangle-Rectangle collision
- Circle-Circle collision
Rectangle Collision
For example, you have two Rectangles:
rect1 = &rigidbody.RigidBody{ Position: vector.Vector{X: 100, Y: 200}, Velocity: vector.Vector{X: 50, Y: -50}, Mass: 1.0, Shape: "Rectangle", Width: 100, Height: 90, IsMovable: true, } rect2 = &rigidbody.RigidBody{ Position: vector.Vector{X: 400, Y: 300}, Velocity: vector.Vector{X: 60, Y: 50}, Mass: 2.0, Shape: "Rectangle", Width: 70, Height: 70, IsMovable: true, }
Now you want to detect collision between them:
if collision.RectangleCollided(rect1, rect2) { fmt.Println("Collided!") }
And if you want to add a bounce effect in this collision according to the Momentum Conservation and Energy Conservation:
if collision.RectangleCollided(rect1, rect2) { float64 e = 0.9999999999; // e is the coefficient of restitution in collision collision.BounceOnCollision(rect1, rect2, e) // NOTE: e<1 is a bit glitchy and goes wild, use it at your own risk :) }
Circle Collision
Now if you want to detect collisions between a circle and a circle:
if collision.CircleCollided(rect1, rect2) { fmt.Println("Collided!") }
And use the same BounceOnCollision function for bouncing.
Springs
Springs can be used to simulate elastic connections between rigid bodies. To create a spring, you need to define two rigid bodies and specify the spring’s stiffness and damping properties.
Example:
spring := spring.NewSpring(ballA, ballB, stiffness, damping)
To apply the spring force in your simulation loop:
This will apply the forces based on Hooke’s Law and damping to the connected rigid bodies.
Examples
Check examples in the ./examples folder.
Some Dynamics
Physics
To update our entity, we have two functions: ApplyForce and ApplyForcePolygon, as the name suggests, one is for RigidBody and one for polygons.
This function will move one frame forward or ‘dt’ time forward (which is the time between two frames).
NOTE: Define dt (0.1 mostly) at the top globally for good code.
ball = &rigidbody.RigidBody{ Position: vector.Vector{X: 400, Y: 100}, Velocity: vector.Vector{X: 0, Y: 2}, Mass: 1, Force: vector.Vector{X: 0, Y: 5}, IsMovable: true, } physix.ApplyForce(ball, vector.Vector{X: 10, Y: 0}, dt) // To apply force on the rigid body
To get both utilities in the code, import this file:
import ( ... "github.com/rudransh61/Physix-go/dynamics/physics" ... )
Contributing
New contributors are welcome! If you have any doubts related to its working, you can ask us by opening an issue.
License
See LICENSE.md file.
Acknowledgments
Inspired by Coding Train – Daniel Shiffman
