On 6/20/2022 6:29 PM, Jacob Kauffmann via ntg-context wrote:

Dear list,

...

Am 01.09.2021 um 09:54 schrieb Jacob Kauffmann via ntg-context ntg-context@ntg.nl:

• color by value in lmt_surface

We want to show a surface plot of a function where the color indicates the function value (instead, or in addition to a light source). The easiest would be to have variable cf for the brightness factor (as it is), and in addition variables such as zt, minz, maxz, akin to the color formatter for lmt_contour. This becomes handy when colors are to be aligned with function values (e.g. negative = blue, zero = white, positive = red, see MWE attached).

I managed to achieve this by tweaking f_color and mp.lmt_surface_do in mlib-cnt.lmt in ConTeXt ver: 2022.05.11 11:36 LMTX fmt: 2022.6.20 a bit. Please find the diff and a MWE attached.

in next version (next time just send me the file, easier than a diff)

Cheers, Jacob Kauffmann

--- context/tex/texmf-context/tex/context/base/mkxl/mlib-cnt.lmt 2022-06-20 18:11:51.000000000 +0200 +++ mlib-cnt.lmt 2022-06-20 18:26:22.000000000 +0200 @@ -1839,7 +1839,29 @@

local f_color = formatters [ [[ local math = math

• return function(f)

• local min = math.min
• local max = math.max
• local abs = math.abs
• local minz = %s
• local maxz = %s
• local color_value = 0
• local color_step = mp.lmt_color_functions.step
• local color_shade = mp.lmt_color_functions.shade
• local function step(...)

•    return color_step(color_value,n,...)
  

• end
• local function shade(...)

•    return color_shade(color_value,n,...)
  

• end
• -- local function lin(l)
• -- return l/n
• -- end
• %s
• return function(z, f)

•    function_value = z
  

•    brightness_factor = f
      return %s
  end
  

  ]] ]

@@ -1898,7 +1920,7 @@ local dy = (ymax - ymin) / ny local xt = xmin --

• local minf, maxf

• local minf, maxf, minz, maxz

  -- similar as contours but no data loop here

@@ -1908,12 +1930,6 @@ return false -- fatal error end --

• local ccode = load(f_color(colorcode))
• local color = type(ccode) == "function" and ccode()
• if type(color) ~= "function" then

•    return false -- fatal error
  

• end

---

  for i=0,nx do
      local yt = ymin
      for j=0,ny do

@@ -1946,7 +1962,16 @@ maxf = fac end --

•        data[i][j] = { x, y, fac }
  

•        if not minz then
  

•           minz = z
  

•           maxz = z
  

•        elseif z < minz then
  

•           minz = z
  

•        elseif z > maxz then
  

•           maxz = z
  

•        end
  

•        --
  

•        data[i][j] = { x, y, fac, z }
          --
          yt = yt + dy
      end
  

@@ -1957,6 +1982,16 @@ local range = maxf - minf local cl = linecolor or 1 local enforce = attributes.colors.model == "cmyk"

• --
• -- local ccode = load(f_color(colorcode))
• report("minz, maxz is (%s,%s)",minz,maxz)
• report("colorcode is %s", colorcode)
• local ccode = load(f_color(minz, maxz, preamble, colorcode))
• local color = type(ccode) == "function" and ccode()
• if type(color) ~= "function" then

•    return false -- fatal error
  

• end
• -- for i=0,nx-1 do for j=0,ny-1 do -- points

@@ -1985,12 +2020,13 @@ local z32 = z3[2] local z41 = z4[1] local z42 = z4[2]

•        local zout = z1[4]
       -- if lines then
       --     -- fill first and draw then, previous shapes can be covered
       -- else
       --     -- fill and draw in one go to prevent artifacts
       -- end
  

•        local cr, cg, cb = color(cf)
  

•        local cr, cg, cb = color(zout, cf)
          if not cr then cr = 0 end
          if not cg then cg = 0 end
          if not cb then cb = 0 end
  
  
  
  
  

---

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