mieki256's diary

function love.conf(t)
  t.window.title = "Shader test 10 sphere"
  t.window.vsync = true
  t.window.resizable = true
  t.window.width = 640
  t.window.height = 480
  -- t.window.fullscreen = true
  -- t.window.fullscreentype = "exclusive"
end

-- Shader test 10 sphere

function love.load()
  love.graphics.setDefaultFilter("nearest", "nearest")
  scr_w, scr_h = 640, 480
  canvas = love.graphics.newCanvas(scr_w, scr_h)

  img = love.graphics.newImage("star_bg_1024x1024.png")
  -- img = love.graphics.newImage("uvcheckermap01-1024.png")
  img:setFilter("linear", "linear")

  -- make shader
  local shadercode = [[
    extern number scr_dist;
    extern number r;
    extern number scale;
    extern number start_x;
    extern number start_y;

    vec4 effect( vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords ) {
      float sx = (screen_coords.x - (love_ScreenSize.x / 2)) / love_ScreenSize.x;
      float sy = (screen_coords.y - (love_ScreenSize.y / 2)) / love_ScreenSize.x;
      // float sx = texture_coords.x - 0.5;
      // float sy = texture_coords.y - 0.5;
      float ang_v = atan(sy, scr_dist);
      float ang_u = atan(sx, scr_dist);
      float pz = r * cos(ang_v);
      float qz = pz * cos(ang_u);
      float u = sx * qz / scr_dist;
      float v = sy * qz / scr_dist;
      texture_coords.x = mod((u + start_x) * scale + 0.5, 1.0);
      texture_coords.y = mod((v + start_y) * scale + 0.5, 1.0);
      vec4 texcolor = Texel(texture, texture_coords);
      return texcolor * color;
    }
  ]]
  myshader = love.graphics.newShader(shadercode)
  local angle_of_view = 60
  local scr_dist = math.cos(math.rad(angle_of_view/2))
  myshader:send("scr_dist", scr_dist)
  myshader:send("r", scr_dist + 0.1)
  myshader:send("scale", 0.4)
  myshader:send("start_x", 0.0)
  myshader:send("start_y", 0.0)

  ang_a = 0.0
  ang_b = 0.0
  px = (scr_w - img:getWidth()) / 2
  py = (scr_h - img:getHeight()) / 2
end

function love.update(dt)
  ang_a = ang_a + 10 * dt
  ang_b = ang_b + 16 * dt
  myshader:send("start_x", (1.0 - math.sin(math.rad(ang_a))))
  myshader:send("start_y", (1.0 - math.sin(math.rad(ang_b))))
end

function love.draw()
  love.graphics.setCanvas(canvas)
  love.graphics.clear(0, 0, 0, 255)

  love.graphics.setColor(255, 255, 255)
  love.graphics.setShader(myshader)
  love.graphics.draw(img, px, py)
  love.graphics.setShader()

  love.graphics.setCanvas()

  -- draw canvas to window
  wdw_w, wdw_h = love.graphics.getDimensions()
  scr_scale = math.min((wdw_w / scr_w), (wdw_h / scr_h))
  scr_ox = (wdw_w - (scr_w * scr_scale)) / 2
  scr_oy = (wdw_h - (scr_h * scr_scale)) / 2
  love.graphics.setColor(255, 255, 255)
  love.graphics.draw(canvas, scr_ox, scr_oy, 0, scr_scale, scr_scale)

  love.graphics.print("FPS: "..tostring(love.timer.getFPS()), 10, 10)
end

function love.keypressed(key, isrepeat)
  if key == "escape" then
    -- ESC to exit
    love.event.quit()
  elseif key == "f11" then
    -- toggle fullscreen
    if love.window.getFullscreen() then
      love.window.setFullscreen(false)
    else
      love.window.setFullscreen(true)
    end
  end
end

• sz : 視点(0,0,0) から画面までの距離。
• sy : 画面を通る直線のy値。
• P : 球と交差する点。
• pz : 球と交差する点のz座標。
• a : 垂直方向の角度。
• r : 球の半径。

a = atan(sy, sz)
pz = r * cos(a)

b = atan(sx, z)
qz = pz * cos(b)

u = sx * qz / sz
v = sy * qz / sz