From 16d14ce7ffc1e70269fda8d375f1da11c3907af8 Mon Sep 17 00:00:00 2001
From: Tim Vaughan <timv@ughan.xyz>
Date: Fri, 24 Feb 2023 14:14:25 +0100
Subject: [PATCH] Added image pigment.

---
 Textures.lua    | 53 ++++++++++++++++++++++++++++++++++++++++++++++---
 mandel_wall.lua | 34 ++++++++++++++++++++-----------
 2 files changed, 72 insertions(+), 15 deletions(-)

diff --git a/Textures.lua b/Textures.lua
index 2b2e701..ccc7dbc 100644
--- a/Textures.lua
+++ b/Textures.lua
@@ -63,16 +63,63 @@ local function make_solid_pigment(colour)
    end
 end
 
-local function make_checkered_pigment(colour1, colour2)
+local function make_checkered_pigment(pigment1, pigment2)
    return function(x,y)
       if (x%1 < 0.5 and y%1 < 0.5) or (x%1 > 0.5 and y%1 > 0.5) then
-         return colour1
+         return pigment1(x,y)
       else
-         return colour2
+         return pigment2(x,y)
       end
    end
 end
 
+local function make_image_pigment(filename,scale)
+
+   print("Loading image pigmant from '" .. filename .. "'...")
+
+   local f = assert(io.open(filename, "rb"))
+   local data = f:read("*all")
+   f:close()
+
+   local start,_,wstr,hstr,dstr,raster =
+      string.find(data, "^P6[%s%c]+(%d+)[%s%c]+(%d+)[%s%c]+(%d+)[%s%c](.*)$")
+
+   if start ~= 1 then
+      error("Error reading image. Is it in PPM(P6) format?")
+   end
+
+   if dstr ~= "255" then
+      error("Only images with a depth of 255 are supported.")
+   end
+
+   local width = tonumber(wstr)
+   local height = tonumber(hstr)
+   local depth = tonumber(dstr)
+
+   local pixels = {}
+   local i = 1
+   for triple in string.gmatch(raster, "...") do
+      local _,_,r,g,b = string.find(triple, "(.)(.)(.)")
+      pixels[i] = {string.byte(r)/depth, string.byte(g)/depth, string.byte(b)/depth}
+      i = i + 1
+   end
+   
+   print("done.")
+   print("(Read " .. tostring(#pixels) .. " pixels.)")
+
+   local pixels_per_unit = math.max(width,height)
+
+   return function(x,y)
+      local xi = math.floor(((x+0.5)*pixels_per_unit/scale)%width) + 1
+      local yi = math.floor(((y+0.5)*pixels_per_unit/scale)%height) + 1
+      local i = width*(yi-1) + xi
+      if pixels[i] == nil then
+         error("Pixel not found at xi=" .. tostring(xi) .. " yi=" .. tostring(yi))
+      end
+      return pixels[i]
+   end
+end
+
 local function make_mandelbrot_pigment(set_pigment, nonset_pigment, max_iter)
 
    local function get_col(x,y,cx,cy,iter)
diff --git a/mandel_wall.lua b/mandel_wall.lua
index 127a27b..3c1f741 100644
--- a/mandel_wall.lua
+++ b/mandel_wall.lua
@@ -12,6 +12,8 @@ local T = Textures
 
 require "Render"
 
+
+
 local lights = {V.new{1,-1,1}}
 
 local plane_normal = V.normalize(V.new{0.0,-1,0.0})
@@ -19,21 +21,29 @@ local texture_y = V.normalize(V.cross(plane_normal,V.x))
 local texture_x = V.cross(texture_y,plane_normal)
 
 local scene = {
-   -- sdf = P.make_plane(V.new{0,0,0}, plane_normal,
-   --                    T.make_phong_texture(lights,
-   --                                         T.map_rectangular(
-   --                                            T.make_mandelbrot_pigment(
-   --                                               T.make_checkered_pigment({0.5,0.2,1.0},{1,1,1}),
-   --                                               T.make_checkered_pigment({1,1,1},{0.5,0.2,1.0}),
-   --                                               20),
-   --                                            texture_x, texture_y),
-   --                                         0.2, 1.0, 0, 1)),
-
-   sdf = P.make_plane(V.origin, plane_normal, T.make_phong_texture(lights,T.map_rectangular(T.make_solid_pigment({0.5,0.2,1.0}), texture_x, texture_y), 0.2, 1.0, 0.5, 20)),
+   sdf = P.make_plane(V.new{0,0,0}, plane_normal,
+                      T.make_phong_texture(lights,
+                                           T.map_rectangular(
+                                              T.make_mandelbrot_pigment(
+                                                 make_image_pigment("images/wood1.ppm",1),
+                                                 make_image_pigment("images/wood2.ppm",1),
+                                                 20),
+                                              texture_x, texture_y),
+                                           0.2, 1.0, 0, 1)),
+
+   -- sdf = P.make_plane(V.origin, plane_normal,
+   --                    T.make_phong_texture(
+   --                       lights,
+   --                       T.map_rectangular(
+   --                          -- T.make_solid_pigment({0.5,0.2,1.0}),
+   --                          T.make_checkered_pigment(
+   --                             make_image_pigment("images/wood1.ppm", 1),
+   --                             make_image_pigment("images/wood2.ppm", 1)),
+   --                          texture_x, texture_y), 0.2, 1.0, 0.5, 20)),
                                
    camera = {location = V.new{0,-5,0},
              point_at = V.new{0,0,0},
              right = V.x,
              fov = 1}}
 
-Render.render(scene, 300, 200, "mandel_wall.ppm")
+Render.render(scene, 1280, 960, "mandel_wall.ppm")
-- 
2.20.1