cycloid

main.go

@@ -0,0 +1,69 @@
+package main
+
+import (
+	"fmt"
+	"math"
+
+	rl "github.com/gen2brain/raylib-go/raylib"
+)
+
+const HEIGHT = 600
+const WIDTH = 800
+
+func main() {
+    fmt.Println("hello world")
+    rl.SetConfigFlags(rl.FlagMsaa4xHint)
+    rl.InitWindow(WIDTH, HEIGHT, "raylib [core] example - basic window")
+    defer rl.CloseWindow()
+    // rl.SetTargetFPS(60)
+
+    rl.BeginDrawing()
+    rl.ClearBackground(rl.RayWhite)
+    rl.EndDrawing()
+
+    var innerCircleRadius float32 = HEIGHT/2
+    var outerCircleRadius float32 = innerCircleRadius/2
+    trace := true
+
+    for !rl.WindowShouldClose() {
+        rl.BeginDrawing()
+        if !trace {
+            rl.ClearBackground(rl.RayWhite)
+        }
+
+        if rl.IsKeyPressed(rl.KeySpace) {
+            trace = !trace
+        }
+
+        angle := float64(rl.GetTime() * 1)
+        center := rl.NewVector2(WIDTH/2, HEIGHT/2)
+        outerCircle := rl.NewVector2(float32(math.Cos(angle)), float32(math.Sin(angle)))
+        outerCircle = rl.Vector2Scale(outerCircle, innerCircleRadius - outerCircleRadius)
+        outerCircle = rl.Vector2Add(outerCircle, center)
+
+        if !trace {
+            // outer circle
+            rl.DrawCircleV(outerCircle, outerCircleRadius, rl.Black)
+            rl.DrawCircleV(outerCircle, outerCircleRadius-1, rl.RayWhite)
+            rl.DrawLineV(outerCircle, center, rl.Black)
+        }
+
+        var tipSize float32 = 6
+        if trace {
+            tipSize = 2
+        }
+        // tip
+        angle *= -7.3
+        tip := rl.NewVector2(float32(math.Cos(angle)), float32(math.Sin(angle)))
+        tip = rl.Vector2Scale(tip, outerCircleRadius)
+        tip = rl.Vector2Add(tip, outerCircle)
+        rl.DrawCircleV(tip, tipSize, rl.Blue)
+
+        if !trace {
+            // inner circle
+            rl.DrawCircleLines(WIDTH/2, HEIGHT/2, innerCircleRadius, rl.Black)
+        }
+
+        rl.EndDrawing()
+    }
+}