imPlot3DDemo.nelua

-- Notice:
--   Compile with Clang compiler.
--
--
require 'os'
require'math'
--
require'cimgui'
require'simple'
require'imgui_backend_opengl3'
require'imgui_backend_glfw'
require'loadImage'
require'utils'
require'IconsFontAwesome6'
--
require'cimplot'
--
require'cimplot3d'

--- External functions
local function setupFonts() <cimport> end                -- from utils/setupFonts.c

--- Initial Window size
local MainWinWidth <const>  = 1280
local MainWinHeight <const> = 800

--- Constants
local IMPLOT_AUTO: float32 = -1

--- Global vars
local versions : [][2]int32 = {{4, 6} ,{4, 5} ,{4, 4} ,{4, 3} ,{4, 2} ,{4, 1} ,{4, 0} ,{3, 3} }

--- Forward definitions

---------
--- main
---------
local main = function()
  glfwInit()
  defer glfwTerminate()  end
  local glfwWin: *GLFWwindow = nilptr
  local glsl_version:cstring -- = "#version 330"
  for _, ver in ipairs(versions) do
    glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE)
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, ver[0])
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, ver[1])
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE)
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE)
    glfwWindowHint(GLFW_RESIZABLE, GLFW_TRUE)

    glfwWin = glfwCreateWindow(MainWinWidth, MainWinHeight, "ImGui with Nelua 2025/05", nilptr, nilptr)
    if nilptr ~= glfwWin then
      glsl_version = "#version " .. tostring( ver[0] * 100 + ver[1] * 10)
      break
    end
  end
  if nilptr == glfwWin then
    print("Could not create window")
    os.exit(false)
  end
  defer glfwDestroyWindow(glfwWin) end

  glfwMakeContextCurrent(glfwWin)
  glfwSwapInterval(1) -- # Enable vsync

  ------------------------
  --- Load title bar icon
  ------------------------
  local IconName = "res/img/nl.png"
  LoadTitleBarIcon(glfwWin, IconName)

  if gladLoadGL(glfwGetProcAddress) == 0 then
    error 'Could not initialize GLAD'
  end
  print('OpenGL loaded:', (@cstring)(glGetString(GL_VERSION)))

  local context = ImGui_CreateContext()
  defer ImGui_DestroyContext(context) end

  ImGui_ImplGlfw_InitForOpenGL(glfwWin, true)
  defer ImGui_ImplGlfw_Shutdown() end

  ImGui_ImplOpenGL3_Init(glsl_version)
  defer ImGui_ImplOpenGL3_Shutdown() end

  setupFonts()

  --igStyleColorsDark()
  ImGui_StyleColorsClassic()

  local showWindowDelay = 1 -- TODO : Avoid flickering window at start up.
  local clearColor: [3]cfloat = {0.03,0.15,0.2}

  local pio = ImGui_GetIO()

  --------------------------
  --- ImPlot/ImPlot3D create context
  --------------------------
  local imPlotContext = ImPlot_CreateContext()
  defer ImPlot_DestroyContext(imPlotContext) end
  --- 3D
  local imPlot3DContext = ImPlot3D_CreateContext()
  defer ImPlot3D_DestroyContext(imPlot3DContext) end

  --------------------
  --- Main while loop
  --------------------
  while glfwWindowShouldClose(glfwWin) == 0 do
    glfwPollEvents()

    ImGui_ImplOpenGL3_NewFrame() -- # start imgui frame
    ImGui_ImplGlfw_NewFrame()
    ImGui_NewFrame()

    ImPlot3D_ShowDemoWindow(nilptr)

    ---------------------
    --- DemoSurfacePlots
    ---------------------
    do ImGui_Begin("ImPlot3D Surface plots with Nelua lang. " .. ICON_FA_CHART_COLUMN, nilptr, 0)
      defer ImGui_End() end
      -- Static vars
      local N <const> = 20
      local xs: [400]float32 <static>
      local ys: [400]float32 <static>
      local zs: [400]float32 <static>
      local t:float32 <static> = 0.0
      --
      local  selected_fill:cint <static> = 1 -- Colormap by default
      local  sel_colormap :cint <static> = 5 -- Jet by default

      local  solid_color <static> = ImVec4_c{0.8, 0.8, 0.2, 0.6}
      -- Generate colormaps
      local colormaps:[]cstring <static> = {"Viridis", "Plasma", "Hot", "Cool", "Pink", "Jet", "Twilight", "RdBu", "BrBG", "PiYG", "Spectral", "Greys"}
      --
      local custom_range      <static> = false
      local range_min:float32 <static> = -1.0
      local range_max:float32 <static> = 1.0

      ImGui_Text("Frame rate  %.3f ms/frame (%.1f FPS)" , 1000.0 / pio.Framerate, pio.Framerate)
      t = t + ImGui_GetIO().DeltaTime
      -- Define the range for X and Y
      local min_val = -1.0
      local max_val = 1.0
      local step = (max_val - min_val) / (N - 1)
      -- Populate the xs, ys, and zs arrays
      for i=0, N -1 do
        local j = 0
        while j < N do
          local  idx = i * N + j
          xs[idx] = min_val + j * step -- X values are constant along rows
          ys[idx] = min_val + i * step -- Y values are constant along columns
          zs[idx] = math.sin(2 * t + math.sqrt((xs[idx] * xs[idx] + ys[idx] * ys[idx]))) -- z = sin(2t + sqrt(x^2 + y^2))
          j = j + 1
        end
      end
      -- Choose fill color
      ImGui_Text("Fill color")
      do ImGui_Indent()
        -- Choose solid color
        ImGui_RadioButtonIntPtr("Solid", &selected_fill, 0)
        if selected_fill == 0 then
          ImGui_SameLine()
          ImGui_ColorEdit4("##SurfaceSolidColor", (@pointer(array(float32,4)))(&solid_color), 0)
        end
        -- Choose colormap
        ImGui_RadioButtonIntPtr("Colormap", &selected_fill, 1)
        if selected_fill == 1 then
          ImGui_SameLine()
          ImGui_ComboChar("##SurfaceColormap", &sel_colormap, &colormaps, #colormaps)
        end
        ImGui_Unindent()
      end

      -- Choose range
      ImGui_Checkbox("Custom range", &custom_range)
      do ImGui_Indent()
        if not custom_range then ImGui_BeginDisabled() end
        ImGui_SliderFloat("Range min", &range_min, -1.0               , range_max - 0.01)
        ImGui_SliderFloat("Range max", &range_max, range_min + 0.01, 1.0)
        if not custom_range then ImGui_EndDisabled() end
        ImGui_Unindent()
      end
      -- Begin the plot
      if selected_fill == 1 then
        ImPlot3D_PushColormap_Str(colormaps[sel_colormap])
      end
      if ImPlot3D_BeginPlot("Surface Plots", ImVec2_c{-1, 400}, ImPlot3DFlags_NoClip) then
        -- Set styles
        ImPlot3D_SetupAxesLimits(-1, 1, -1, 1, -1.5, 1.5)
        ImPlot3D_PushStyleVar_Float(ImPlot3DStyleVar_FillAlpha, 0.8)
        if selected_fill == 0 then
          ImPlot3D_SetNextFillStyle(solid_color)
        end
        local IMPLOT3D_AUTO <const> =  -1                       -- Deduce variable automatically
        local vec4:ImVec4_c
        vec4 =  ImPlot3D_GetColormapColor(1, IMPLOT3D_AUTO)
        ImPlot3D_SetNextLineStyle(vec4, IMPLOT3D_AUTO)

        -- Plot the surface
        if custom_range then
          ImPlot3D_PlotSurface_FloatPtr("Wave Surface", &xs, &ys, &zs, N, N, range_min, range_max, 0, 0, #float32)
        else
          ImPlot3D_PlotSurface_FloatPtr("Wave Surface", &xs, &ys, &zs, N, N, 0, 0, 0, 0, #float32)
        end
        -- End the plot
        ImPlot3D_PopStyleVar()
        ImPlot3D_EndPlot()
      end
      if selected_fill == 1 then
        ImPlot3D_PopColormap()
      end
    end

    ---------
    ImGui_Render()
    glClearColor(clearColor[0], clearColor[1], clearColor[2], 1.0)
    glClear(GL_COLOR_BUFFER_BIT)
    ImGui_ImplOpenGL3_RenderDrawData(ImGui_GetDrawData())

    glfwSwapBuffers(glfwWin)

    if showWindowDelay > 0 then
      showWindowDelay = showWindowDelay - 1
    elseif showWindowDelay == 0 then
      showWindowDelay = -1
      glfwShowWindow(glfwWin)
    end
  end -- main while loop end

end -- main() end

main()