new files

Task/Death-Star/Go/death-star.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+    "fmt"
+    "image"
+    "image/color"
+    "image/png"
+    "math"
+    "os"
+)
+
+type vector [3]float64
+
+func (v *vector) normalize() {
+    invLen := 1 / math.Sqrt(dot(v, v))
+    v[0] *= invLen
+    v[1] *= invLen
+    v[2] *= invLen
+}
+
+func dot(x, y *vector) float64 {
+    return x[0]*y[0] + x[1]*y[1] + x[2]*y[2]
+}
+
+type sphere struct {
+    cx, cy, cz int
+    r          int
+}
+
+func (s *sphere) hit(x, y int) (z1, z2 float64, hit bool) {
+    x -= s.cx
+    y -= s.cy
+    if zsq := s.r*s.r - (x*x + y*y); zsq >= 0 {
+        zsqrt := math.Sqrt(float64(zsq))
+        return float64(s.cz) - zsqrt, float64(s.cz) + zsqrt, true
+    }
+    return 0, 0, false
+}
+
+func deathStar(pos, neg *sphere, k, amb float64, dir *vector) *image.Gray {
+    w, h := pos.r*4, pos.r*3
+    bounds := image.Rect(pos.cx-w/2, pos.cy-h/2, pos.cx+w/2, pos.cy+h/2)
+    img := image.NewGray(bounds)
+    vec := new(vector)
+    for y, yMax := pos.cy-pos.r, pos.cy+pos.r; y <= yMax; y++ {
+        for x, xMax := pos.cx-pos.r, pos.cx+pos.r; x <= xMax; x++ {
+            zb1, zb2, hit := pos.hit(x, y)
+            if !hit {
+                continue
+            }
+            zs1, zs2, hit := neg.hit(x, y)
+            if hit {
+                if zs1 > zb1 {
+                    hit = false
+                } else if zs2 > zb2 {
+                    continue
+                }
+            }
+            if hit {
+                vec[0] = float64(neg.cx - x)
+                vec[1] = float64(neg.cy - y)
+                vec[2] = float64(neg.cz) - zs2
+            } else {
+                vec[0] = float64(x - pos.cx)
+                vec[1] = float64(y - pos.cy)
+                vec[2] = zb1 - float64(pos.cz)
+            }
+            vec.normalize()
+            s := dot(dir, vec)
+            if s < 0 {
+                s = 0
+            }
+            lum := 255 * (math.Pow(s, k) + amb) / (1 + amb)
+            if lum < 0 {
+                lum = 0
+            } else if lum > 255 {
+                lum = 255
+            }
+            img.SetGray(x, y, color.Gray{uint8(lum)})
+        }
+    }
+    return img
+}
+
+func main() {
+    dir := &vector{20, -40, -10}
+    dir.normalize()
+    pos := &sphere{0, 0, 0, 120}
+    neg := &sphere{-90, -90, -30, 100}
+
+    img := deathStar(pos, neg, 1.5, .2, dir)
+    f, err := os.Create("dstar.png")
+    if err != nil {
+        fmt.Println(err)
+        return
+    }
+    if err = png.Encode(f, img); err != nil {
+        fmt.Println(err)
+    }
+    if err = f.Close(); err != nil {
+        fmt.Println(err)
+    }
+}