From 9e67a8260fee8f8a423a3131bcf13db3b9de6922 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Thu, 27 Jun 2024 15:43:38 +0100
Subject: maths.Pow turned out to be seriously terrible

---
 .gitignore  | 4 +++-
 hittable.go | 4 ++--
 material.go | 9 ++++++---
 rtiaw.go    | 9 +++++++++
 4 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/.gitignore b/.gitignore
index fddca93..5abb052 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
 *.swp
+*.prof
 rtiaw
-out.ppm
+*.ppm
+*.png
diff --git a/hittable.go b/hittable.go
index ac5e996..73e2e3c 100644
--- a/hittable.go
+++ b/hittable.go
@@ -42,8 +42,8 @@ func (s Sphere) Hit(r Ray, ray_t Interval) (rec HitRecord) {
   oc := s.Origin.Sub(r.Origin);
   a := r.Direction.MagSqr();
   h := r.Direction.Dot(oc);
-  c := oc.MagSqr() - maths.Pow(s.Radius, 2);
-  disc := maths.Pow(h, 2) - a*c;
+  c := oc.MagSqr() - s.Radius * s.Radius;
+  disc := h * h - a * c;
 
   if disc < 0 {
     return;
diff --git a/material.go b/material.go
index 62a0467..6b3a528 100644
--- a/material.go
+++ b/material.go
@@ -65,7 +65,7 @@ func (d Dielectric) Scatter(r Ray, hit HitRecord) Ray {
 
   unit_dir := r.Direction.Unit();
   cos_theta := maths.Min(unit_dir.Neg().Dot(hit.N), 1.0);
-  sin_theta := maths.Sqrt(1.0 - maths.Pow(cos_theta, 2));
+  sin_theta := maths.Sqrt(1.0 - cos_theta * cos_theta);
 
   cannot_refract := ri * sin_theta > 1.0;
 
@@ -80,7 +80,10 @@ func (d Dielectric) Scatter(r Ray, hit HitRecord) Ray {
 }
 
 func schlick_reflect(cos_theta float64, ri float64) bool {
-  r0 := maths.Pow((1 - ri) / (1 + ri), 2);
-  approx := r0 + (1 - r0) * maths.Pow(1 - cos_theta, 5);
+  r0 := (1 - ri) / (1 + ri);
+  r0 = r0 * r0;
+  ct5 := 1 - cos_theta;
+  ct5 = ct5 * ct5 * ct5 * ct5 * ct5;
+  approx := r0 + (1 - r0) * ct5;
   return approx > Interval{0, 1}.Sample();
 }
diff --git a/rtiaw.go b/rtiaw.go
index 392db71..2daa826 100644
--- a/rtiaw.go
+++ b/rtiaw.go
@@ -1,6 +1,15 @@
 package main
 
+import (
+  "os"
+  "runtime/pprof"
+)
+
 func main() {
+  f, _ := os.Create("rtiaw.prof");
+  pprof.StartCPUProfile(f);
+  defer pprof.StopCPUProfile();
+
   var world Hittables;
 
   mat_ground := Lambertian{Vec3{0.5, 0.5, 0.5}};
-- 
cgit v1.2.1