working on a physics example

examples/marblemachine/main.go

@@ -0,0 +1,203 @@
+package main
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"math"
+	"math/rand"
+	"time"
+
+	"github.com/GaryBrownEEngr/scratch"
+	"github.com/GaryBrownEEngr/scratch/models"
+	"github.com/GaryBrownEEngr/scratch/tools"
+	"github.com/fogleman/gg"
+	"github.com/jakecoffman/cp"
+)
+
+func main() {
+	params := scratch.ScratchParams{Width: 1000, Height: 1000, ShowFPS: true}
+	scratch.Start(params, simStartFunc)
+}
+
+type object struct {
+	sprite       models.Sprite
+	physicsShape *cp.Shape
+}
+
+func simStartFunc(sim models.Scratch) {
+	oList := []*object{}
+
+	space := cp.NewSpace()
+	space.SetGravity(cp.Vector{X: 0, Y: -600})
+
+	container := space.AddBody(cp.NewKinematicBody())
+	container.SetAngularVelocity(0.4)
+	container.SetPosition(cp.Vector{0, 0})
+
+	a := cp.Vector{-200, -200}
+	b := cp.Vector{-200, 200}
+	c := cp.Vector{200, 200}
+	d := cp.Vector{200, -200}
+
+	AddWall(space, container, a, b, 1)
+	AddWall(space, container, b, c, 1)
+	AddWall(space, container, c, d, 1)
+	AddWall(space, container, d, a, 1)
+
+	mass := 1.0
+	width := 30.0
+	height := width * 2
+
+	for i := 0; i < 7; i++ {
+		for j := 0; j < 3; j++ {
+			pos := cp.Vector{X: float64(i) * width, Y: float64(j) * height}
+
+			typ := rand.Intn(3)
+			if typ == 0 {
+				// AddBox(space, pos, mass, width, height)
+			} else if typ == 1 {
+				// AddSegment(space, pos, mass, width, height)
+			} else {
+				a := AddCircle(sim, space, pos.Add(cp.Vector{X: 0, Y: (height - width) / 2}), mass, width/2)
+				b := AddCircle(sim, space, pos.Add(cp.Vector{X: 0, Y: (width - height) / 2}), mass, width/2)
+				oList = append(oList, a, b)
+
+			}
+		}
+	}
+
+	for {
+		time.Sleep(time.Millisecond)
+		space.Step(.010)
+
+		for _, o := range oList {
+			b := o.physicsShape.Body()
+			p := b.Position()
+			o.sprite.Pos(p.X, p.Y)
+			o.sprite.Angle(180.0 / math.Pi * b.Angle())
+
+		}
+	}
+
+}
+
+func createCircleImage(radius float64, c color.Color) image.Image {
+	dc := gg.NewContext(int(radius*3), int(radius*3))
+	dc.DrawCircle(radius*1.5, radius*1.5, radius)
+	dc.SetColor(c)
+	dc.Fill()
+	dc.SetColor(tools.White)
+	dc.SetLineWidth(3)
+	dc.DrawLine(radius*1.5, radius*1.5, radius*2.0, radius*1.5)
+	dc.Stroke()
+
+	return dc.Image()
+}
+
+func createRectangleImage(width, height float64, c color.Color) image.Image {
+	dc := gg.NewContext(int(width), int(height))
+	dc.DrawRectangle(0, 0, width, height)
+	dc.SetColor(c)
+	dc.Fill()
+	return dc.Image()
+}
+
+// func createContainer(sim models.Scratch, space *cp.Space) []*object {
+// 	container := space.AddBody(cp.NewKinematicBody())
+// 	container.SetAngularVelocity(0.4)
+// 	container.SetPosition(cp.Vector{X: 0, Y: 0})
+
+// 	container
+// 	shape := space.AddShape(circle.Shape)
+
+// 	a := cp.Vector{X: -200, Y: -200}
+// 	b := cp.Vector{X: -200, Y: 200}
+// 	c := cp.Vector{X: 200, Y: 200}
+// 	d := cp.Vector{X: 200, Y: -200}
+
+// 	AddWall(space, container, a, b, 1)
+// 	AddWall(space, container, b, c, 1)
+// 	AddWall(space, container, c, d, 1)
+// 	AddWall(space, container, d, a, 1)
+
+// 	ret := &object{
+// 		sprite:       sprite,
+// 		physicsShape: shape,
+// 	}
+
+// 	return ret
+// }
+
+func AddWall(space *cp.Space, body *cp.Body, a, b cp.Vector, radius float64) {
+	// swap so we always draw the same direction horizontally
+	if a.X < b.X {
+		a, b = b, a
+	}
+
+	seg := cp.NewSegment(body, a, b, radius).Class.(*cp.Segment)
+	shape := space.AddShape(seg.Shape)
+	shape.SetElasticity(1)
+	shape.SetFriction(1)
+
+}
+
+func AddSegment(space *cp.Space, pos cp.Vector, mass, width, height float64) *cp.Shape {
+	body := space.AddBody(cp.NewBody(mass, cp.MomentForBox(mass, width, height)))
+	body.SetPosition(pos)
+
+	a, b := cp.Vector{X: 0, Y: (height - width) / 2.0}, cp.Vector{X: 0, Y: (width - height) / 2.0}
+	seg := cp.NewSegment(body, a, b, width/2.0).Class.(*cp.Segment)
+	shape := space.AddShape(seg.Shape)
+	shape.SetElasticity(0)
+	shape.SetFriction(0.7)
+
+	return shape
+}
+
+func AddBox(sim models.Scratch, space *cp.Space, pos cp.Vector, mass, width, height float64) *object {
+	body := space.AddBody(cp.NewBody(mass, cp.MomentForBox(mass, width, height)))
+	body.SetPosition(pos)
+
+	shape := space.AddShape(cp.NewBox(body, width, height, 0))
+	shape.SetElasticity(0)
+	shape.SetFriction(0.7)
+
+	c := color.RGBA{R: uint8(rand.Intn(256)), G: uint8(rand.Intn(256)), B: uint8(rand.Intn(256)), A: 0xFF}
+	costumeName := fmt.Sprintf("%X", rand.Uint64())
+	sim.AddCostume(createRectangleImage(width, height, c), costumeName)
+	sprite := sim.AddSprite("")
+	sprite.Costume(costumeName)
+	sprite.Pos(pos.X, pos.Y)
+	sprite.Visible(true)
+
+	ret := &object{
+		sprite:       sprite,
+		physicsShape: shape,
+	}
+	return ret
+}
+
+func AddCircle(sim models.Scratch, space *cp.Space, pos cp.Vector, mass, radius float64) *object {
+	body := space.AddBody(cp.NewBody(mass, cp.MomentForCircle(mass, 0, radius, cp.Vector{})))
+	body.SetPosition(pos)
+
+	circle := cp.NewCircle(body, radius, cp.Vector{}).Class.(*cp.Circle)
+	shape := space.AddShape(circle.Shape)
+	shape.SetElasticity(0)
+	shape.SetFriction(0.7)
+
+	c := color.RGBA{R: uint8(rand.Intn(256)), G: uint8(rand.Intn(256)), B: uint8(rand.Intn(256)), A: 0xFF}
+	costumeName := fmt.Sprintf("%X", rand.Uint64())
+	sim.AddCostume(createCircleImage(radius, c), costumeName)
+	sprite := sim.AddSprite("")
+	sprite.Costume(costumeName)
+	sprite.Pos(pos.X, pos.Y)
+	sprite.Visible(true)
+
+	ret := &object{
+		sprite:       sprite,
+		physicsShape: shape,
+	}
+	return ret
+}

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/fogleman/gg v1.3.0
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
 	github.com/hajimehoshi/ebiten/v2 v2.6.3
+	github.com/jakecoffman/cp v1.2.1
 	github.com/stretchr/testify v1.8.4
 	golang.org/x/image v0.14.0
 )

go.sum

@@ -13,6 +13,8 @@ github.com/hajimehoshi/ebiten/v2 v2.6.3/go.mod h1:TZtorL713an00UW4LyvMeKD8uXWnuI
 github.com/hajimehoshi/go-mp3 v0.3.4 h1:NUP7pBYH8OguP4diaTZ9wJbUbk3tC0KlfzsEpWmYj68=
 github.com/hajimehoshi/go-mp3 v0.3.4/go.mod h1:fRtZraRFcWb0pu7ok0LqyFhCUrPeMsGRSVop0eemFmo=
 github.com/hajimehoshi/oto/v2 v2.3.1/go.mod h1:seWLbgHH7AyUMYKfKYT9pg7PhUu9/SisyJvNTT+ASQo=
+github.com/jakecoffman/cp v1.2.1 h1:zkhc2Gpo9l4NLUZfeG3j33+3bQD7MkqPa+n5PdX+5mI=
+github.com/jakecoffman/cp v1.2.1/go.mod h1:JjY/Fp6d8E1CHnu74gWNnU0+b9VzEdUVPoJxg2PsTQg=
 github.com/jezek/xgb v1.1.0 h1:wnpxJzP1+rkbGclEkmwpVFQWpuE2PUGNUzP8SbfFobk=
 github.com/jezek/xgb v1.1.0/go.mod h1:nrhwO0FX/enq75I7Y7G8iN1ubpSGZEiA3v9e9GyRFlk=
 github.com/jfreymuth/oggvorbis v1.0.5 h1:u+Ck+R0eLSRhgq8WTmffYnrVtSztJcYrl588DM4e3kQ=