implemented graphviz builderin dot.go to build dot files for graphviz

internal/viz/dot.go

@@ -1,3 +1,37 @@
 package viz
 
-//init
+import (
+	"bspviz/internal/bsp"
+	"bytes"
+	"fmt"
+	"os"
+)
+
+func EmitDOT(root *bsp.Node, path string) error {
+	var buf bytes.Buffer
+	buf.WriteString("digraph BSP {\n")
+	buf.WriteString("  node [fontname=\"Helvetica\"];\n")
+
+	id := 0
+	var walk func(*bsp.Node) int
+	walk = func(n *bsp.Node) int {
+		my := id
+		id++
+		if n.Leaf != nil {
+			fmt.Fprintf(&buf, "  n%d [label=\"Leaf\\nSegs=%d\", shape=ellipse, style=filled, fillcolor=lightgray];\n",
+				my, len(n.Leaf.Segs))
+			return my
+		}
+		fmt.Fprintf(&buf, "  n%d [label=\"Split\\nO=(%.0f,%.0f) D=(%.0f,%.0f)\"];\n",
+			my, n.O.X, n.O.Y, n.D.X, n.D.Y)
+		l := walk(n.Left)
+		r := walk(n.Right)
+		fmt.Fprintf(&buf, "  n%d -> n%d [label=\"L\"];\n", my, l)
+		fmt.Fprintf(&buf, "  n%d -> n%d [label=\"R\"];\n", my, r)
+		return my
+	}
+	walk(root)
+
+	buf.WriteString("}\n")
+	return os.WriteFile(path, buf.Bytes(), 0644)
+}

main.go

@@ -4,6 +4,7 @@ import (
 	"bspviz/internal/bsp"
 	"bspviz/internal/geom"
 	"bspviz/internal/mapfmt"
+	"bspviz/internal/viz"
 	"bspviz/internal/wad"
 	"flag"
 	"fmt"
@@ -30,6 +31,7 @@ func main() {
 	depth := flag.Int("maxdepth", 32, "max. Rekursionstiefe")
 	cands := flag.Int("cands", 16, "Anzahl Kandidaten (Subsample)")
 	seed := flag.Int64("seed", 0, "RNG-Seed (0 = default)")
+	dotOut := flag.String("dot", "", "DOT-Export-Datei (optional)")
 
 	flag.Parse()
 
@@ -190,6 +192,14 @@ func main() {
 			st.Nodes, st.Leaves, st.MaxDepth, st.TotalSegs)
 		fmt.Printf("  params: alpha=%.2f beta=%.2f eps=%.1e leafMax=%d maxDepth=%d cands=%d seed=%d\n",
 			p.Alpha, p.Beta, p.Eps, p.LeafMax, p.MaxDepth, p.Cands, p.Seed)
+
+		if *dotOut != "" {
+			if err := viz.EmitDOT(root, *dotOut); err != nil {
+				log.Fatalf("write DOT: %v", err)
+			}
+			fmt.Printf("DOT export geschrieben: %s (mit 'dot -Tpng %s -o tree.png' rendern)\n",
+				*dotOut, *dotOut)
+		}
 		return
 	}