mirror of
https://github.com/charmbracelet/harmonica.git
synced 2026-07-20 02:29:33 -06:00
84 lines
2.5 KiB
Go
84 lines
2.5 KiB
Go
// Simple physics projectile motion.
|
|
//
|
|
// Example usage:
|
|
//
|
|
// // Run once to initialize.
|
|
// projectile := NewProjectile(FPS(60), Point{6.0, 100.0, 0.0}, Vector{2.0, 0.0, 0.0}, Vector{2.0, -9.81, 0.0})
|
|
//
|
|
// // Update on every frame.
|
|
// someUpdateLoop(func() {
|
|
// pos := projectile.Update()
|
|
// })
|
|
//
|
|
// For background on projectile motion see:
|
|
// https://en.wikipedia.org/wiki/Projectile_motion
|
|
package harmonica
|
|
|
|
// Projectile is the representation of a projectile that has a position on a
|
|
// plane and an acceleration and velocity
|
|
type Projectile struct {
|
|
pos Point
|
|
vel Vector
|
|
acc Vector
|
|
deltaTime float64
|
|
}
|
|
|
|
// Point is a representation of a point which contains the X, Y, Z coordinates
|
|
// of the point on a plane.
|
|
type Point struct {
|
|
X, Y, Z float64
|
|
}
|
|
|
|
// Vector is a representation of a vector which carries a magnitude and a
|
|
// direction. We represent the vector as a point from the origin (0, 0) where
|
|
// the magnitude is the euclidean distance from the origin and the direction is
|
|
// the direction to the point from the origin.
|
|
type Vector struct {
|
|
X, Y, Z float64
|
|
}
|
|
|
|
// Gravity is a utility vector that represents gravity in 2D and 3D contexts,
|
|
// assuming that your coordinate plane looks like in 2D or 3D:
|
|
//
|
|
// y y ±z
|
|
// │ │ /
|
|
// │ │/
|
|
// └───── ±x └───── ±x
|
|
//
|
|
// (i.e. origin is located in the bottom-left corner)
|
|
var Gravity = Vector{0, -9.81, 0}
|
|
|
|
// TerminalGravity is a utility vector that represents gravity where
|
|
// the coordinate plane's origin is on the top-right corner
|
|
var TerminalGravity = Vector{0, 9.81, 0}
|
|
|
|
// NewProjectile accepts a frame rate, and initial values for position, velocity, and acceleration and
|
|
// returns a new projectile.
|
|
func NewProjectile(deltaTime float64, initialPosition Point, initialVelocity, initalAcceleration Vector) Projectile {
|
|
return Projectile{
|
|
pos: initialPosition,
|
|
vel: initialVelocity,
|
|
acc: initalAcceleration,
|
|
deltaTime: deltaTime,
|
|
}
|
|
}
|
|
|
|
// Update updates the position and velocity values for the given projectile.
|
|
// Call this after calling NewProjectile to update values.
|
|
func (p *Projectile) Update() Point {
|
|
p.pos.X += (p.vel.X * p.deltaTime)
|
|
p.pos.Y += (p.vel.Y * p.deltaTime)
|
|
p.pos.Z += (p.vel.Z * p.deltaTime)
|
|
|
|
p.vel.X += (p.acc.X * p.deltaTime)
|
|
p.vel.Y += (p.acc.Y * p.deltaTime)
|
|
p.vel.Z += (p.acc.Z * p.deltaTime)
|
|
|
|
return p.pos
|
|
}
|
|
|
|
// Position returns the position of the projectile
|
|
func (p *Projectile) Position() Point {
|
|
return p.pos
|
|
}
|