Init, test raylib & math things

bouncing_ball.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	rl "github.com/gen2brain/raylib-go/raylib"
+)
+
+func main() {
+	screenWidth := int32(800)
+	screenHeight := int32(450)
+
+	rl.InitWindow(screenWidth, screenHeight, "Bouncing Ball in Go - raylib")
+	defer rl.CloseWindow()
+
+	rl.SetTargetFPS(60)
+
+	// Ball properties
+	ballRadius := float32(20)
+	ballPos := rl.NewVector2(float32(screenWidth)/2.0, float32(screenHeight)/2.0)
+	ballSpeed := rl.NewVector2(4, 3)
+	ballColor := rl.Red
+
+	for !rl.WindowShouldClose() {
+		// Update
+		ballPos.X += ballSpeed.X
+		ballPos.Y += ballSpeed.Y
+
+		// Bounce on edges
+		if ballPos.X >= float32(screenWidth)-ballRadius || ballPos.X <= ballRadius {
+			ballSpeed.X *= -1
+		}
+		if ballPos.Y >= float32(screenHeight)-ballRadius || ballPos.Y <= ballRadius {
+			ballSpeed.Y *= -1
+		}
+
+		// Draw
+		rl.BeginDrawing()
+		rl.ClearBackground(rl.RayWhite)
+
+		rl.DrawText("Bouncing Ball Example", 10, 10, 20, rl.DarkGray)
+		rl.DrawCircleV(ballPos, ballRadius, ballColor)
+
+		rl.EndDrawing()
+	}
+}

go.mod

@@ -0,0 +1,10 @@
+module test_raylib
+
+go 1.24.7
+
+require (
+	github.com/ebitengine/purego v0.9.0 // indirect
+	github.com/gen2brain/raylib-go/raylib v0.55.1 // indirect
+	golang.org/x/exp v0.0.0-20250911091902-df9299821621 // indirect
+	golang.org/x/sys v0.36.0 // indirect
+)

go.sum

@@ -0,0 +1,8 @@
+github.com/ebitengine/purego v0.9.0 h1:mh0zpKBIXDceC63hpvPuGLiJ8ZAa3DfrFTudmfi8A4k=
+github.com/ebitengine/purego v0.9.0/go.mod h1:iIjxzd6CiRiOG0UyXP+V1+jWqUXVjPKLAI0mRfJZTmQ=
+github.com/gen2brain/raylib-go/raylib v0.55.1 h1:1rdc10WvvYjtj7qijHnV9T38/WuvlT6IIL+PaZ6cNA8=
+github.com/gen2brain/raylib-go/raylib v0.55.1/go.mod h1:BaY76bZk7nw1/kVOSQObPY1v1iwVE1KHAGMfvI6oK1Q=
+golang.org/x/exp v0.0.0-20250911091902-df9299821621 h1:2id6c1/gto0kaHYyrixvknJ8tUK/Qs5IsmBtrc+FtgU=
+golang.org/x/exp v0.0.0-20250911091902-df9299821621/go.mod h1:TwQYMMnGpvZyc+JpB/UAuTNIsVJifOlSkrZkhcvpVUk=
+golang.org/x/sys v0.36.0 h1:KVRy2GtZBrk1cBYA7MKu5bEZFxQk4NIDV6RLVcC8o0k=
+golang.org/x/sys v0.36.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=

sdf.go

@@ -0,0 +1,67 @@
+package main
+
+const EPS = 0.001
+
+type SDF interface {
+	Distance(Vector3) float64
+}
+
+func Gradient(sdf SDF, p Vector3, eps float64) Vector3 {
+	dx := (sdf.Distance(p.Add(Vector3{X: eps})) - sdf.Distance(p.Add(Vector3{X: -eps}))) / (2 * eps)
+	dy := (sdf.Distance(p.Add(Vector3{Y: eps})) - sdf.Distance(p.Add(Vector3{Y: -eps}))) / (2 * eps)
+	dz := (sdf.Distance(p.Add(Vector3{Z: eps})) - sdf.Distance(p.Add(Vector3{Z: -eps}))) / (2 * eps)
+	return Vector3{X: dx, Y: dy, Z: dz}
+}
+
+// Some transformations see https://iquilezles.org/articles/distfunctions/
+
+type translatedSDF struct {
+	primitive SDF
+	translate Vector3
+}
+
+func (s translatedSDF) Distance(p Vector3) float64 {
+	return s.primitive.Distance(p.Sub(s.translate))
+}
+
+type rotatedSDF struct {
+	primitive SDF
+	rotVector Vector3
+	angle     float64
+}
+
+func (s rotatedSDF) Distance(p Vector3) float64 {
+	rotated_p := rotate(p, s.rotVector, s.angle)
+	return s.primitive.Distance(rotated_p)
+}
+
+type scaledSDF struct {
+	primitive SDF
+	scale     float64
+}
+
+func (s scaledSDF) Distance(p Vector3) float64 {
+	return s.primitive.Distance(p.Scale(1/s.scale)) * s.scale
+}
+
+type infiniteRep struct {
+	primitive SDF
+	cellSize  Vector3
+}
+
+// TODO
+// func (s infiniteRep) Distance(p Vector3) float64 {
+// 	x, y, z := p.Unpack()
+// 	sx, sy, sz := s.cellSize.Unpack()
+// }
+
+// Sphere
+
+type Sphere struct {
+	center Vector3
+	radius float64
+}
+
+func (s Sphere) Distance(p Vector3) float64 {
+	return p.Sub(s.center).Length()
+}

vec3.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"math"
+)
+
+type Vector3 struct {
+	X, Y, Z float64
+}
+
+func (u Vector3) Add(v Vector3) Vector3 {
+	return Vector3{u.X + v.X, u.Y + v.Y, u.Z + v.Z}
+}
+
+func (u Vector3) Neg() Vector3 {
+	return Vector3{-u.X, -u.Y, -u.Z}
+}
+
+func (u Vector3) Sub(v Vector3) Vector3 {
+	return u.Add(v.Neg())
+}
+
+func (u Vector3) Scale(a float64) Vector3 {
+	return Vector3{a * u.X, a * u.Y, a * u.Z}
+}
+
+func (u Vector3) Dot(v Vector3) float64 {
+	return u.X*v.X + u.Y*v.Y + u.Z*v.Z
+}
+
+func (u Vector3) Cross(v Vector3) Vector3 {
+	return Vector3{u.Y*v.Z - u.Z*v.Y, u.Z*v.X - u.X*v.Z, u.X*v.Y - u.Y*v.X}
+}
+
+func (u Vector3) LengthSquared() float64 {
+	return u.Dot(u)
+}
+
+func (u Vector3) Length() float64 {
+	return math.Sqrt(u.LengthSquared())
+}
+
+func (u Vector3) Normalized() Vector3 {
+	return u.Scale(1.0 / u.Length())
+}
+
+func (u Vector3) Round() Vector3 {
+	round := math.Round
+	return Vector3{round(u.X), round(u.Y), round(u.Z)}
+}
+
+// i incident, n normal. Both vector should be normalized
+func Reflect(i Vector3, n Vector3) Vector3 {
+	y := i.Dot(n)
+	return i.Add(n.Scale(2 * y))
+}
+
+// Todo : Refract
+
+// Rodrigues' rotation formula. rotVector should be normalized
+func rotate(u Vector3, rotVector Vector3, angle float64) Vector3 {
+	cos, sin := math.Cos(angle), math.Sin(angle)
+	vec1 := u.Scale(cos)
+	vec2 := rotVector.Cross(u).Scale(sin)
+	vec3 := rotVector.Scale(rotVector.Dot(u) * (1 - cos))
+	return vec1.Add(vec2).Add(vec3)
+}
+
+func (v Vector3) Unpack() (float64, float64, float64) {
+	return v.X, v.Y, v.Z
+}