use jakecoffman port of chipmunk instead of vova616

examples/physics/chipmunk/main.go

@@ -1,139 +1,163 @@
 package main
 
 import (
+	"fmt"
 	"math"
 	"math/rand"
 
 	"github.com/gen2brain/raylib-go/raylib"
-
+	"github.com/jakecoffman/cp"
-	"github.com/vova616/chipmunk"
-	"github.com/vova616/chipmunk/vect"
 )
 
-const (
+var grabbableMaskBit uint = 1 << 31
-	ballRadius = 25
+var grabFilter = cp.ShapeFilter{
-	ballMass   = 1
+	cp.NO_GROUP, grabbableMaskBit, grabbableMaskBit,
-)
-
-// Game type
-type Game struct {
-	Space       *chipmunk.Space
-	Balls       []*chipmunk.Shape
-	StaticLines []*chipmunk.Shape
-
-	ticksToNextBall int
 }
 
-// NewGame - Start new game
+func randUnitCircle() cp.Vector {
-func NewGame() (g Game) {
+	v := cp.Vector{X: rand.Float64()*2.0 - 1.0, Y: rand.Float64()*2.0 - 1.0}
-	g.Init()
+	if v.LengthSq() < 1.0 {
-	return
+		return v
+	}
+	return randUnitCircle()
 }
 
-// Init - Initialize game
+var simpleTerrainVerts = []cp.Vector{
-func (g *Game) Init() {
+	{350.00, 425.07}, {336.00, 436.55}, {272.00, 435.39}, {258.00, 427.63}, {225.28, 420.00}, {202.82, 396.00},
-	g.createBodies()
+	{191.81, 388.00}, {189.00, 381.89}, {173.00, 380.39}, {162.59, 368.00}, {150.47, 319.00}, {128.00, 311.55},
-
+	{119.14, 286.00}, {126.84, 263.00}, {120.56, 227.00}, {141.14, 178.00}, {137.52, 162.00}, {146.51, 142.00},
-	g.ticksToNextBall = 10
+	{156.23, 136.00}, {158.00, 118.27}, {170.00, 100.77}, {208.43, 84.00}, {224.00, 69.65}, {249.30, 68.00},
+	{257.00, 54.77}, {363.00, 45.94}, {374.15, 54.00}, {386.00, 69.60}, {413.00, 70.73}, {456.00, 84.89},
+	{468.09, 99.00}, {467.09, 123.00}, {464.92, 135.00}, {469.00, 141.03}, {497.00, 148.67}, {513.85, 180.00},
+	{509.56, 223.00}, {523.51, 247.00}, {523.00, 277.00}, {497.79, 311.00}, {478.67, 348.00}, {467.90, 360.00},
+	{456.76, 382.00}, {432.95, 389.00}, {417.00, 411.32}, {373.00, 433.19}, {361.00, 430.02}, {350.00, 425.07},
 }
 
-// Update - Update game
+// creates a circle with random placement
-func (g *Game) Update() {
+func addCircle(space *cp.Space, radius float64) {
-	g.ticksToNextBall--
+	mass := radius * radius / 25.0
-	if g.ticksToNextBall == 0 {
+	body := space.AddBody(cp.NewBody(mass, cp.MomentForCircle(mass, 0, radius, cp.Vector{})))
-		g.ticksToNextBall = rand.Intn(100) + 1
+	body.SetPosition(randUnitCircle().Mult(180))
-		g.addBall()
+
+	shape := space.AddShape(cp.NewCircle(body, radius, cp.Vector{}))
+	shape.SetElasticity(0)
+	shape.SetFriction(0.9)
 }
 
-	// Physics steps calculations
+// creates a simple terrain to contain bodies
-	g.step(raylib.GetFrameTime())
+func simpleTerrain() *cp.Space {
+	space := cp.NewSpace()
+	space.Iterations = 10
+	space.SetGravity(cp.Vector{0, -100})
+	space.SetCollisionSlop(0.5)
+
+	offset := cp.Vector{X: -320, Y: -240}
+	for i := 0; i < len(simpleTerrainVerts)-1; i++ {
+		a := simpleTerrainVerts[i]
+		b := simpleTerrainVerts[i+1]
+		space.AddShape(cp.NewSegment(space.StaticBody, a.Add(offset), b.Add(offset), 0))
 	}
 
-// Draw - Draw game
+	return space
-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")
+	const width, height = 800, 450
+	const physicsTickrate = 1.0 / 60.0
 
-	raylib.SetTargetFPS(60)
+	raylib.SetConfigFlags(raylib.FlagVsyncHint)
+	raylib.InitWindow(width, height, "raylib [physics] example - chipmunk")
 
-	game := NewGame()
+	offset := raylib.Vector2{X: width / 2, Y: height / 2}
+	// since the example ported from elsewhere, flip the camera 180 and offset to center it
+	camera := raylib.NewCamera2D(offset, raylib.Vector2{}, 180, 1)
 
+	space := simpleTerrain()
+	for i := 0; i < 1000; i++ {
+		addCircle(space, 5)
+	}
+	mouseBody := cp.NewKinematicBody()
+	var mouse cp.Vector
+	var mouseJoint *cp.Constraint
+
+	var accumulator, dt float32
+	lastTime := raylib.GetTime()
 	for !raylib.WindowShouldClose() {
+		// calculate dt
+		now := raylib.GetTime()
+		dt = now - lastTime
+		lastTime = now
+
+		// update the mouse position
+		mousePos := raylib.GetMousePosition()
+		// alter the mouse coordinates based on the camera position, rotation
+		mouse.X = float64(mousePos.X-camera.Offset.X) * -1
+		mouse.Y = float64(mousePos.Y-camera.Offset.Y) * -1
+		// smooth mouse movements to new position
+		newPoint := mouseBody.Position().Lerp(mouse, 0.25)
+		mouseBody.SetVelocityVector(newPoint.Sub(mouseBody.Position()).Mult(60.0))
+		mouseBody.SetPosition(newPoint)
+
+		// handle grabbing
+		if raylib.IsMouseButtonPressed(raylib.MouseLeftButton) {
+			result := space.PointQueryNearest(mouse, 5, grabFilter)
+			if result.Shape != nil && result.Shape.Body().Mass() < cp.INFINITY {
+				var nearest cp.Vector
+				if result.Distance > 0 {
+					nearest = result.Point
+				} else {
+					nearest = mouse
+				}
+
+				// create a new constraint where the mouse is to draw the body towards the mouse
+				body := result.Shape.Body()
+				mouseJoint = cp.NewPivotJoint2(mouseBody, body, cp.Vector{}, body.WorldToLocal(nearest))
+				mouseJoint.SetMaxForce(50000)
+				mouseJoint.SetErrorBias(math.Pow(1.0-0.15, 60.0))
+				space.AddConstraint(mouseJoint)
+			}
+		} else if raylib.IsMouseButtonReleased(raylib.MouseLeftButton) && mouseJoint != nil {
+			space.RemoveConstraint(mouseJoint)
+			mouseJoint = nil
+		}
+
+		// perform a fixed rate physics tick
+		accumulator += dt
+		for accumulator >= physicsTickrate {
+			space.Step(physicsTickrate)
+			accumulator -= physicsTickrate
+		}
+
 		raylib.BeginDrawing()
-
 		raylib.ClearBackground(raylib.RayWhite)
+		raylib.BeginMode2D(camera)
 
-		game.Update()
+		// this is a generic way to iterate over the shapes in a space,
-
+		// to avoid the type switch just keep a pointer to the shapes when they've been created
-		game.Draw()
+		space.EachShape(func(s *cp.Shape) {
+			switch s.Class.(type) {
+			case *cp.Segment:
+				segment := s.Class.(*cp.Segment)
+				a := segment.A()
+				b := segment.B()
+				raylib.DrawLineV(v(a), v(b), raylib.Black)
+			case *cp.Circle:
+				circle := s.Class.(*cp.Circle)
+				pos := circle.Body().Position()
+				raylib.DrawCircleV(v(pos), float32(circle.Radius()), raylib.Red)
+			default:
+				fmt.Println("unexpected shape", s.Class)
+			}
+		})
 
+		raylib.EndMode2D()
+		raylib.DrawFPS(0, 0)
 		raylib.EndDrawing()
 	}
 
 	raylib.CloseWindow()
 }
+
+func v(v cp.Vector) raylib.Vector2 {
+	return raylib.Vector2{X: float32(v.X), Y: float32(v.Y)}
+}