Physics examples

examples/physics/chipmunk/main.go

@@ -0,0 +1,139 @@
+package main
+
+import (
+	"math"
+	"math/rand"
+
+	"github.com/gen2brain/raylib-go/raylib"
+
+	"github.com/vova616/chipmunk"
+	"github.com/vova616/chipmunk/vect"
+)
+
+const (
+	ballRadius = 25
+	ballMass   = 1
+)
+
+// Game type
+type Game struct {
+	Space       *chipmunk.Space
+	Balls       []*chipmunk.Shape
+	StaticLines []*chipmunk.Shape
+
+	ticksToNextBall int
+}
+
+// NewGame - Start new game
+func NewGame() (g Game) {
+	g.Init()
+	return
+}
+
+// Init - Initialize game
+func (g *Game) Init() {
+	g.createBodies()
+
+	g.ticksToNextBall = 10
+}
+
+// Update - Update game
+func (g *Game) Update() {
+	g.ticksToNextBall--
+	if g.ticksToNextBall == 0 {
+		g.ticksToNextBall = rand.Intn(100) + 1
+		g.addBall()
+	}
+
+	// Physics steps calculations
+	g.step(raylib.GetFrameTime())
+}
+
+// Draw - Draw game
+func (g *Game) Draw() {
+	for i := range g.StaticLines {
+		x := g.StaticLines[i].GetAsSegment().A.X
+		y := g.StaticLines[i].GetAsSegment().A.Y
+
+		x2 := g.StaticLines[i].GetAsSegment().B.X
+		y2 := g.StaticLines[i].GetAsSegment().B.Y
+
+		raylib.DrawLine(int32(x), int32(y), int32(x2), int32(y2), raylib.DarkBlue)
+	}
+
+	for _, b := range g.Balls {
+		pos := b.Body.Position()
+		raylib.DrawCircleLines(int32(pos.X), int32(pos.Y), float32(ballRadius), raylib.DarkBlue)
+	}
+}
+
+// createBodies sets up the chipmunk space and static bodies
+func (g *Game) createBodies() {
+	g.Space = chipmunk.NewSpace()
+	g.Space.Gravity = vect.Vect{0, 900}
+
+	staticBody := chipmunk.NewBodyStatic()
+	g.StaticLines = []*chipmunk.Shape{
+		chipmunk.NewSegment(vect.Vect{250.0, 240.0}, vect.Vect{550.0, 280.0}, 0),
+		chipmunk.NewSegment(vect.Vect{550.0, 280.0}, vect.Vect{550.0, 180.0}, 0),
+	}
+
+	for _, segment := range g.StaticLines {
+		segment.SetElasticity(0.6)
+		staticBody.AddShape(segment)
+	}
+
+	g.Space.AddBody(staticBody)
+}
+
+// addBall adds ball to chipmunk space and body
+func (g *Game) addBall() {
+	x := rand.Intn(600-200) + 200
+	ball := chipmunk.NewCircle(vect.Vector_Zero, float32(ballRadius))
+	ball.SetElasticity(0.95)
+
+	body := chipmunk.NewBody(vect.Float(ballMass), ball.Moment(float32(ballMass)))
+	body.SetPosition(vect.Vect{vect.Float(x), 0.0})
+	body.SetAngle(vect.Float(rand.Float32() * 2 * math.Pi))
+	body.AddShape(ball)
+
+	g.Space.AddBody(body)
+	g.Balls = append(g.Balls, ball)
+}
+
+// step advances the physics engine and cleans up any balls that are off-screen
+func (g *Game) step(dt float32) {
+	g.Space.Step(vect.Float(dt))
+
+	for i := 0; i < len(g.Balls); i++ {
+		p := g.Balls[i].Body.Position()
+		if p.Y < -100 {
+			g.Space.RemoveBody(g.Balls[i].Body)
+			g.Balls[i] = nil
+			g.Balls = append(g.Balls[:i], g.Balls[i+1:]...)
+			i-- // consider same index again
+		}
+	}
+}
+
+func main() {
+	raylib.InitWindow(800, 450, "raylib [physics] example - chipmunk")
+
+	raylib.SetTargetFPS(60)
+
+	game := NewGame()
+
+	for !raylib.WindowShouldClose() {
+		raylib.BeginDrawing()
+
+		raylib.ClearBackground(raylib.RayWhite)
+
+		game.Update()
+
+		game.Draw()
+
+		raylib.EndDrawing()
+	}
+
+	raylib.CloseWindow()
+}