From bb9573c800572e7426b458d6551cd30cac8d1d72 Mon Sep 17 00:00:00 2001
From: Tim Vaughan <timv@ughan.xyz>
Date: Thu, 23 Feb 2023 11:54:30 +0100
Subject: [PATCH] Added mandelbrot pigment.

---
 Textures.lua | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Textures.lua b/Textures.lua
index 1e919c7..1456f7d 100644
--- a/Textures.lua
+++ b/Textures.lua
@@ -68,6 +68,32 @@ local function make_checkered_pigment(colour1, colour2)
       end
    end
 end
+
+local function make_mandelbrot_pigment()
+
+   local maxiter = 100
+   local set_colour = {0,0,0}
+
+   local function get_col(x,y,cx,cy,iter)
+      if iter == 0 then
+         return set_colour
+      elseif x^2 + y^2 > 4 then
+         local I = iter/max_iter
+         return {I,I,1-I}
+      else
+         return get_col(x^2 - y^2 + cx,
+                        2*x*y + cy,
+                        cx, cy, iter-1)
+      end
+
+      local xp = x^2 - y^2 + cx
+      local yp = 2*x*y + cy
+   end
+
+   return function (x,y)
+      get_col(0,0,x,y,maxiter)
+   end
+end
    
 Textures = {
    make_phong_texture = make_phong_texture,
-- 
2.20.1