Initial data commit

Task/Draw-a-sphere/Go/draw-a-sphere.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+    "fmt"
+    "image"
+    "image/color"
+    "image/png"
+    "math"
+    "os"
+)
+
+type vector [3]float64
+
+func normalize(v *vector) {
+    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]
+}
+
+func drawSphere(r int, k, amb float64, dir *vector) *image.Gray {
+    w, h := r*4, r*3
+    img := image.NewGray(image.Rect(-w/2, -h/2, w/2, h/2))
+    vec := new(vector)
+    for x := -r; x < r; x++ {
+        for y := -r; y < r; y++ {
+            if z := r*r - x*x - y*y; z >= 0 {
+                vec[0] = float64(x)
+                vec[1] = float64(y)
+                vec[2] = math.Sqrt(float64(z))
+                normalize(vec)
+                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{-30, -30, 50}
+    normalize(dir)
+    img := drawSphere(200, 1.5, .2, dir)
+    f, err := os.Create("sphere.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)
+    }
+}