Textures.lua

   1 -- Textures for raymarcher
   2 require "Vector"
   3 local V = Vector
   4
   5 local function make_phong_texture(lights, pigment, amb, diff, spec, shiny)
   6    local normalize = V.normalize
   7
   8    local eps = 0.0001
   9    local function light_visibility(location, light_dir, pos, dest, res, sdf)
  10       local p = sdf(location)
  11       if pos + p.dist > dest then
  12          return res
  13       elseif p.dist < eps then
  14          return 0.0
  15       else
  16          return light_visibility(location + light_dir*p.dist, light_dir, pos+p.dist,
  17                                  dest, math.min(res, 30*p.dist/(pos+p.dist)), sdf)
  18       end
  19    end
  20
  21    return function (location, ray_dir, normal, count, sdf)
  22       local colour = pigment(location[1],location[2])
  23       local thiscol = {colour[1]*amb, colour[2]*amb, colour[3]*amb}
  24
  25       local reflected_ray = ray_dir - normal*(ray_dir*normal*2)
  26       for _,light in ipairs(lights) do
  27          local light_dist = V.norm(light-location)
  28          local light_dir = (light-location)/light_dist
  29
  30          local vis = light_visibility(location + light_dir*eps, light_dir, eps, light_dist, 1, sdf)
  31
  32          local Idiff = math.max(normal*light_dir, 0)
  33          local Ispec = math.pow(math.max(light_dir*reflected_ray,0),shiny)
  34
  35          thiscol[1] = thiscol[1] + vis*(colour[1]*Idiff*diff + Ispec*spec)
  36          thiscol[2] = thiscol[2] + vis*(colour[2]*Idiff*diff + Ispec*spec)
  37          thiscol[3] = thiscol[3] + vis*(colour[3]*Idiff*diff + Ispec*spec)
  38       end
  39
  40       return thiscol
  41    end
  42 end
  43
  44 local function make_count_texture(scale)
  45    return function (location, ray_dir, normal, count, sdf)
  46       return {count*scale, count*scale, count*scale}
  47    end
  48 end
  49
  50 local function make_flat_texture(pigment)
  51    return function (location, ray_dir, normal, count, sdf)
  52       return pigment(location[1], location[2])
  53    end
  54 end
  55
  56 local function make_solid_pigment(colour)
  57    return function (x,y)
  58       return colour
  59    end
  60 end
  61
  62 local function make_checkered_pigment(colour1, colour2)
  63    return function (x,y)
  64       if (x%1 < 0.5 and y%1 < 0.5) or (x%1 > 0.5 and y%1 > 0.5) then
  65          return colour1
  66       else
  67          return colour2
  68       end
  69    end
  70 end
  71
  72 local function make_mandelbrot_pigment(set_colour, max_iter)
  73
  74    local function get_col(x,y,cx,cy,iter)
  75       if iter == 0 then
  76          return set_colour
  77       elseif x^2 + y^2 > 4 then
  78          local I = iter/max_iter
  79          return {I,I,1-I}
  80       else
  81          return get_col(x^2 - y^2 + cx,
  82                         2*x*y + cy,
  83                         cx, cy, iter-1)
  84       end
  85    end
  86
  87    return function (x,y)
  88       get_col(0,0,x,y,max_iter)
  89    end
  90 end
  91
  92 Textures = {
  93    make_phong_texture = make_phong_texture,
  94    make_flat_texture = make_flat_texture,
  95    make_count_texture = make_count_texture,
  96    make_solid_pigment = make_solid_pigment,
  97    make_checkered_pigment = make_checkered_pigment,
  98    make_mandelbrot_pigment = make_mandelbrot_pigment
  99 }
 100
 101 return Textures