From 0c87cf3f007797714755b309ad31602cedb8af1e Mon Sep 17 00:00:00 2001
From: xengineering <mail2xengineering@protonmail.com>
Date: Thu, 20 May 2021 15:24:04 +0200
Subject: Update Documentation

---
 geometry.go |  3 +++
 stl.go      | 17 ++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/geometry.go b/geometry.go
index c9453a9..3c3ba83 100644
--- a/geometry.go
+++ b/geometry.go
@@ -2,18 +2,21 @@
 
 package main
 
+// representation of a three-dimensional point in space
 type Point struct {
 	x float32
 	y float32
 	z float32
 }
 
+// a triangle consists of three points
 type Triangle struct {
 	a *Point
 	b *Point
 	c *Point
 }
 
+// a surface is made of a slice of triangles
 type Surface struct {
 	triangles []*Triangle
 }
diff --git a/stl.go b/stl.go
index ceee2b7..f1d0a60 100644
--- a/stl.go
+++ b/stl.go
@@ -1,5 +1,9 @@
 // vim: shiftwidth=4 tabstop=4 noexpandtab
 
+/*
+Wikipedia about STL file format: https://en.wikipedia.org/wiki/STL_(file_format)
+*/
+
 package main
 
 import (
@@ -9,12 +13,14 @@ import (
 	"math"
 )
 
+// representation of binary STL file content
 type BinaryStl struct {
 	header []byte
 	numberOfTriangles uint32
 	surface Surface
 }
 
+// read and parse a given binary STL file
 func ReadBinaryStlFile(filePath string) (BinaryStl, error) {
 
 	fileContent, err := ioutil.ReadFile(filePath)
@@ -42,21 +48,26 @@ func ReadBinaryStlFile(filePath string) (BinaryStl, error) {
 	return model,nil
 }
 
+// parse the 50 bytes of the STL file representing a triangle (surface normal is ignored)
 func ParseBinaryStlTriangle(data []byte) *Triangle {  // FIXME: This function should only accept 50 byte slices/arrays
 
+	// allocate a new triangle and three corner points on the heap
 	triangle := new(Triangle)
-	triangle.a = new(Point)
-	triangle.b = new(Point)
-	triangle.c = new(Point)
+	triangle.a = new(Point)  // corner point a
+	triangle.b = new(Point)  // corner point b
+	triangle.c = new(Point)  // corner point c
 
+	// parse x, y and z coordinate for corner point a
 	triangle.a.x = math.Float32frombits(binary.LittleEndian.Uint32(data[12:16]))
 	triangle.a.y = math.Float32frombits(binary.LittleEndian.Uint32(data[16:20]))
 	triangle.a.z = math.Float32frombits(binary.LittleEndian.Uint32(data[20:24]))
 
+	// parse x, y and z coordinate for corner point b
 	triangle.b.x = math.Float32frombits(binary.LittleEndian.Uint32(data[24:28]))
 	triangle.b.y = math.Float32frombits(binary.LittleEndian.Uint32(data[28:32]))
 	triangle.b.z = math.Float32frombits(binary.LittleEndian.Uint32(data[32:36]))
 
+	// parse x, y and z coordinate for corner point c
 	triangle.c.x = math.Float32frombits(binary.LittleEndian.Uint32(data[36:40]))
 	triangle.c.y = math.Float32frombits(binary.LittleEndian.Uint32(data[40:44]))
 	triangle.c.z = math.Float32frombits(binary.LittleEndian.Uint32(data[44:48]))
-- 
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