From 512b5c91fc117dac730f150ecd0f1f2f44886667 Mon Sep 17 00:00:00 2001
From: Altagos <altagos@posteo.de>
Date: Fri, 01 Mar 2024 13:15:10 +0000
Subject: [PATCH] fuzzy metal

---
 src/main.zig | 4 ++--
 src/material.zig | 9 ++++++---
 2 file(s) changed, 8 insertion(s)(+), 5 deletion(s)(-)

diff --git a/src/main.zig b/src/main.zig
--- a/src/main.zig
+++ b/src/main.zig
@@ -29,8 +29,8 @@
     // Setting up the world
     var material_ground = Material.lambertian(zm.f32x4(0.8, 0.8, 0.0, 1.0));
     var material_center = Material.lambertian(zm.f32x4(0.7, 0.3, 0.3, 1.0));
-    var material_left = Material.metal(zm.f32x4(0.8, 0.8, 0.8, 1.0));
-    var material_right = Material.metal(zm.f32x4(0.8, 0.6, 0.2, 1.0));
+    var material_left = Material.metal(zm.f32x4(0.8, 0.8, 0.8, 1.0), 0.3);
+    var material_right = Material.metal(zm.f32x4(0.8, 0.6, 0.2, 1.0), 1.0);
 
     var world = HittableList.init(allocator);
     try world.add(Hittable.initSphere(Sphere{ .center = zm.f32x4(0, -100.5, -1, 0), .radius = 100, .mat = &material_ground }));
diff --git a/src/material.zig b/src/material.zig
--- a/src/material.zig
+++ b/src/material.zig
@@ -12,8 +12,8 @@
         return .{ .lambertian = .{ .albedo = albedo } };
     }
 
-    pub fn metal(albedo: zm.Vec) Material {
-        return .{ .metal = .{ .albedo = albedo } };
+    pub fn metal(albedo: zm.Vec, fuzz: f32) Material {
+        return .{ .metal = .{ .albedo = albedo, .fuzz = if (fuzz < 1) fuzz else 1.0 } };
     }
 
     pub fn scatter(self: *Material, r: *Ray, rec: *hittable.HitRecord, attenuation: *zm.Vec) ?Ray {
@@ -39,10 +39,13 @@
 
 pub const Metal = struct {
     albedo: zm.Vec,
+    /// fuzz < 1
+    fuzz: f32,
 
     pub fn scatter(self: *Metal, r: *Ray, rec: *hittable.HitRecord, attenuation: *zm.Vec) ?Ray {
         const reflected = util.reflect(zm.normalize3(r.dir), rec.normal);
+        const scattered = Ray.init(rec.p, reflected + zm.f32x4s(self.fuzz) * util.randomUnitVec());
         attenuation.* = self.albedo;
-        return Ray.init(rec.p, reflected);
+        return if (zm.dot3(scattered.dir, rec.normal)[0] > 0) scattered else null;
     }
 };

--
tangled.sh