From 91b9af0c86db9eb2859ac85609c3a6711f6be12a Mon Sep 17 00:00:00 2001
From: Andy LeClair <andyleclair@gmail.com>
Date: Fri, 29 May 2026 15:58:21 -0400
Subject: [PATCH] metal fuzziness

---
 src/color.ct    |  4 ++++
 src/main.ct     |  8 ++++----
 src/material.ct | 16 ++++++++++------
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/src/color.ct b/src/color.ct
index 491845f..9dbf145 100644
--- a/src/color.ct
+++ b/src/color.ct
@@ -1,6 +1,7 @@
 (cl:defpackage #:ray/color
   (:use #:coalton #:coalton-prelude)
   (:export #:Color
+           #:black
            #:mul
            #:mul-scalar
            #:add))
@@ -13,6 +14,9 @@
     (g F32)
     (b F32))
   
+  (declare black (Void -> Color))
+  (define (black) (Color 0.0 0.0 0.0))
+  
   (declare mul (Color * Color  -> Color))
   (define (mul (Color r g b) (Color r2 g2 b2))
     "Multiply a color by a given scalar value"
diff --git a/src/main.ct b/src/main.ct
index d13fbff..2c5f5d8 100644
--- a/src/main.ct
+++ b/src/main.ct
@@ -80,9 +80,9 @@
     ; Center
     (s:Sphere (v:Vec3 0.0 0.0 -1.2) 0.5 (m:Lambertian (c:Color 0.1 0.2 0.5)))
     ; Left
-    (s:Sphere (v:Vec3 -1.0 0.0 -1.0) 0.5 (m:Metal (c:Color 0.8 0.8 0.8)))
+    (s:Sphere (v:Vec3 -1.0 0.0 -1.0) 0.5 (m:Metal (c:Color 0.8 0.8 0.8) 0.3))
     ; Right
-    (s:Sphere (v:Vec3 1.0 0.0 -1.0) 0.5 (m:Metal (c:Color 0.8 0.6 0.2)))
+    (s:Sphere (v:Vec3 1.0 0.0 -1.0) 0.5 (m:Metal (c:Color 0.8 0.6 0.2) 1.0))
   ])
   
   (define INFINITY (the F32 math:infinity))
@@ -125,7 +125,7 @@
   (declare ray-color (r:Ray * UFix -> c:Color))
   (define (ray-color r depth)
     (cond 
-      ((<= depth 0) (c:Color 0.0 0.0 0.0))
+      ((<= depth 0) (c:black))
       (True
         (match (hit-any? r 0.001 INFINITY)
           ((Some (h:HitRecord point normal _ _ material))
@@ -171,7 +171,7 @@
               :repeat (unwrap-as UFix IMAGE-WIDTH)
                (let color = 
                  (for ((sample 0 (1+ sample)) 
-                        (pixel-color (c:Color 0.0 0.0 0.0) 
+                        (pixel-color (c:black) 
                                      (c:add pixel-color (ray-color (get-ray x y) MAX_DEPTH))))
                       :returns (c:mul-scalar pixel-color PIXEL-SAMPLES-SCALE)
                       :repeat (unwrap-as UFix SAMPLES-PER-PIXEL)
diff --git a/src/material.ct b/src/material.ct
index 91249c2..f44ba6f 100644
--- a/src/material.ct
+++ b/src/material.ct
@@ -13,7 +13,7 @@
 
 (coalton-toplevel
   (define-type Material
-    (Metal c:Color)
+    (Metal c:Color F32)
     (Lambertian c:Color)
     (Dielectric F32))
   
@@ -25,15 +25,19 @@
         (values (Some (r:Ray point normal)) albedo)
         (values (Some (r:Ray point scatter-direction)) albedo)))
   
-  (declare scatter-metal (v:Vec3 * v:Vec3 * v:Vec3 * c:Color -> Optional r:Ray * c:Color))
-  (define (scatter-metal direction point normal albedo)
+  (declare scatter-metal (v:Vec3 * v:Vec3 * v:Vec3 * c:Color * F32 -> Optional r:Ray * c:Color))
+  (define (scatter-metal direction point normal albedo fuzz)
     (let reflected = (v:reflect direction normal))
-    (values (Some (r:Ray point reflected)) albedo))
+    (let re-reflected = (v:vec-add (v:unit-vector reflected)
+                                   (v:vec-mul-scalar (v:random-unit-vector) fuzz)))
+    (if (> (v:vec-dot re-reflected normal) 0)
+        (values (Some (r:Ray point re-reflected)) albedo)
+        (values None (c:black))))
   
   (declare scatter (r:Ray * v:Vec3 * v:Vec3 * Material -> Optional r:Ray * c:Color))
   (define (scatter (r:Ray _ direction) point normal material)
     (match material
       ((Lambertian albedo) (scatter-lambertian point normal albedo))
-      ((Metal albedo) (scatter-metal direction point normal albedo))
-      (_ (values None (c:Color 0.0 0.0 0.0)))))
+      ((Metal albedo fuzz) (scatter-metal direction point normal albedo fuzz))
+      (_ (values None (c:black)))))
 )
\ No newline at end of file
-- 
2.51.2