A script for the Valve flashlight, meant for VR. This fixes bugs, adds some small features, and cleans up the code from the sample here: https://developer.valvesoftware.com/wiki/SteamVR/Environments/Scripting/flashlight_script_code_full

flashlight.lua

-- Disable this flag to remove the glow particle around the flashlight's lens.
local enableGlow = true;
local glowParticle;

local lightTable = {
  classname = "light_spot",
  targetname = "light" .. thisEntity:entindex(),
  enabled = 0,
  brightness = "1.5",
  range = "400",
  castshadows = "1",
  shadowtexturewidth = "64",
  shadowtextureheight = "64",
  style = "0",
  fademindist = "0",
  fademaxdist = "4000",
  bouncescale = "1.0",
  renderdiffuse = "1",
  renderspecular = "1",
  directlight = "2",
  indirectlight = "0",
  attenuation1 = "0.0",
  attenuation2 = "1.0",
  innerconeangle = "20",
  outerconeangle = "32"
}

local isEquipped = false;
local holdingHand;
local holdingHandId = -1; -- 0 is right hand. 1 is the left hand.
local handAttachment;
local player;

local flashlightOn = false;
local particleTrackpad;
local lightEntity;

local trackpadX = 0.0;
local trackpadY = 0.0;

local lightColorsIndex = 13; -- Start at white.
local lightColors = {};
lightColors[1] = { 255, 128, 0 };
lightColors[2] = { 255, 0, 0 };
lightColors[3] = { 255, 0, 64 };
lightColors[4] = { 180, 0, 180 };
lightColors[5] = { 64, 0, 180 };
lightColors[6] = { 0, 0, 255 };
lightColors[7] = { 0, 180, 180 };
lightColors[8] = { 0, 255, 128 };
lightColors[9] = { 0, 255, 0 };
lightColors[10] = { 128, 255, 0 };
lightColors[11] = { 255, 255, 0 };
lightColors[12] = { 255, 180, 0 };
lightColors[13] = { 255, 255, 255 };
local colorWheelCount = 12; -- White is at the center of the wheel.
local colorWheelMaxDegrees = {};

local equippedStartTime = 0;

function SetEquipped(self, pHand, nHandID, pHandAttachment, pPlayer)
  holdingHand = pHand;
  holdingHandId = nHandID;
  handAttachment = pHandAttachment;
  player = pPlayer;
  isEquipped = true;
  equippedStartTime = Time();

  local trackpadParticleName = "particles/tool_fx/controller_trackpad_position_dot.vpcf";
  particleTrackpad = ParticleManager:CreateParticle(trackpadParticleName, PATTACH_POINT_FOLLOW, handAttachment);
  ParticleManager:SetParticleControlEnt(particleTrackpad, 0, handAttachment, PATTACH_POINT_FOLLOW, "trackpad_center", Vector(0, 0, 0), true);

  local degreeChunk = 360.0 / colorWheelCount;
  for i = 1, colorWheelCount do
    local maxDegree = i * degreeChunk;
    colorWheelMaxDegrees[i] = maxDegree;
  end

  if (lightEntity == nil) then
    lightEntity = SpawnEntityFromTableSynchronous(lightTable.classname, lightTable);
  end
  lightEntity:SetParent(handAttachment, "flashlight_beam");
  lightEntity:SetLocalOrigin(Vector(0, 0, 0));
  lightEntity:SetLocalAngles(0, 0, 0);

  if (flashlightOn) then
    EntFireByHandle(self, handAttachment, "Skin", "1", 0);
  end

  ParticleManager:SetParticleControl(particleTrackpad, 1, Vector(-trackpadY, trackpadX, 0));
  ParticleManager:SetParticleControl(particleTrackpad, 2, Vector(lightColors[lightColorsIndex][1], lightColors[lightColorsIndex][2], lightColors[lightColorsIndex][3]));
  EntFireByHandle(self, lightEntity, "setlightcolor", "" .. lightColors[lightColorsIndex][1] .. " " .. lightColors[lightColorsIndex][2] .. " " .. lightColors[lightColorsIndex][3] .. "", 0);

  if (enableGlow) then
    if (flashlightOn) then
      ParticleManager:DestroyParticle(glowParticle, true);
      createGlowParticle(handAttachment);
    end

    holdingHand:SetThink("FlashlightThink", self, 0.0);
  end

  return true;
end

function SetUnequipped()
  holdingHand = nil;
  holdingHandId = -1;
  handAttachment = nil;
  player = nil;
  isEquipped = false;

  lightEntity:SetParent(thisEntity, "flashlight_beam");

  if (particleTrackpad ~= nil) then
    ParticleManager:DestroyParticle(particleTrackpad, true);
    particleTrackpad = nil;
  end

  if (enableGlow and flashlightOn) then
    ParticleManager:DestroyParticle(glowParticle, true);
    createGlowParticle(thisEntity);
  end

  return true;
end

---------------------------------------------------------------------------
-- Get the degrees of an x and y position on a two-dimensional surface.
---------------------------------------------------------------------------
function GetDegrees(x, y)
  local deltaX = 0 - x;
  local deltaY = 0 - y;

  local radAngle = math.atan2(deltaY, deltaX);
  local degreeAngle = radAngle * 180.0 / math.pi;

  return (180.0 - degreeAngle);
end

function Precache(context)
  PrecacheModel("models/props_gameplay/flashlight001.vmdl", context);
  PrecacheParticle("particles/tool_fx/controller_trackpad_position_dot.vpcf", context);
  if (enableGlow) then
    PrecacheParticle("particles/tool_fx/flashlight_thirdperson.vpcf", context);
  end
end

function ChangeColor(newLightColorsIndex)
  if (lightColorsIndex == newLightColorsIndex) then
    return ;
  end
  lightColorsIndex = newLightColorsIndex;
  if (enableGlow and flashlightOn) then
    ParticleManager:SetParticleControl(glowParticle, 5, Vector(lightColors[lightColorsIndex][1], lightColors[lightColorsIndex][2], lightColors[lightColorsIndex][3]));
  end
  EntFireByHandle(self, lightEntity, "setlightcolor", "" .. lightColors[lightColorsIndex][1] .. " " .. lightColors[lightColorsIndex][2] .. " " .. lightColors[lightColorsIndex][3] .. "", 0);
  EmitSoundOn("ui_select", thisEntity);
end

function OnHandleInput(input)
  local holdingHandIN_TRIGGER = IN_USE_HAND1;
  if (holdingHandId == 0) then
    holdingHandIN_TRIGGER = IN_USE_HAND0
  end
  local holdingHandIN_GRIP = IN_GRIP_HAND1;
  if (holdingHandId == 0) then
    holdingHandIN_GRIP = IN_GRIP_HAND0
  end
  local holdingHandIN_PAD_TOUCH_HAND = IN_PAD_TOUCH_HAND1;
  if (holdingHandId == 0) then
    holdingHandIN_PAD_TOUCH_HAND = IN_PAD_TOUCH_HAND0
  end

  if (input.buttonsDown:IsBitSet(holdingHandIN_PAD_TOUCH_HAND)) then
    local updateTrackpad = false;
    local currentTrackpadX = input.trackpadX;
    if (currentTrackpadX ~= trackpadX) then
      trackpadX = currentTrackpadX;
      updateTrackpad = true;
    end
    local currentTrackpadY = input.trackpadY;
    if (currentTrackpadY ~= trackpadY) then
      trackpadY = currentTrackpadY;
      updateTrackpad = true;
    end
    if (updateTrackpad) then
      UpdateTrackpadPosition();
    end
  end

  if (input.buttonsPressed:IsBitSet(holdingHandIN_TRIGGER)) then
    input.buttonsPressed:ClearBit(holdingHandIN_TRIGGER);
    -- Add a delay to prevent the flashlight from turning on when picked up with the trigger.
    if (Time() > equippedStartTime + 0.2) then
      ToggleFlashlight();
    end
  end

  if (input.buttonsReleased:IsBitSet(holdingHandIN_TRIGGER)) then
    input.buttonsReleased:ClearBit(holdingHandIN_TRIGGER);
  end

  if (input.buttonsReleased:IsBitSet(holdingHandIN_GRIP)) then
    input.buttonsReleased:ClearBit(holdingHandIN_GRIP);
    thisEntity:ForceDropTool();
  end

  return input;
end

function UpdateTrackpadPosition()
  local degree = GetDegrees(trackpadX, trackpadY);
  local distance = math.sqrt((trackpadX ^ 2) + (trackpadY ^ 2));
  if (distance < 0.24) then
    -- The center of the trackpad is the white selection.
    ChangeColor(13);
  else
    local minDegree = 0
    for i = 1, colorWheelCount do
      local maxDegree = colorWheelMaxDegrees[i];
      if (degree >= minDegree and degree < maxDegree) then
        ChangeColor(i);
        break ;
      end
      minDegree = maxDegree;
    end
  end

  ParticleManager:SetParticleControl(particleTrackpad, 1, Vector(-trackpadY, trackpadX, 0));
  ParticleManager:SetParticleControl(particleTrackpad, 2, Vector(lightColors[lightColorsIndex][1], lightColors[lightColorsIndex][2], lightColors[lightColorsIndex][3]));
end

function ToggleFlashlight()
  if (flashlightOn) then
    TurnFlashlightOff()
  else
    TurnFlashlightOn();
  end
  holdingHand:FireHapticPulse(1); -- 1 is the heavy rumble.
end

function TurnFlashlightOn()
  flashlightOn = true;
  -- Borrow the drone sound.
  EmitSoundOn("drone_equip", thisEntity);
  EntFireByHandle(self, handAttachment, "Skin", "1", 0);
  EntFireByHandle(self, thisEntity, "Skin", "1", 0);
  EntFireByHandle(self, lightEntity, "TurnOn", "", 0);

  if (enableGlow) then
    createGlowParticle(handAttachment);
  end
end

function TurnFlashlightOff()
  flashlightOn = false;
  -- Borrow the drone sound.
  EmitSoundOn("drone_equip", thisEntity);
  EntFireByHandle(self, handAttachment, "Skin", "0", 0);
  EntFireByHandle(self, thisEntity, "Skin", "0", 0);
  EntFireByHandle(self, lightEntity, "TurnOff", "", 0);

  if (enableGlow) then
    ParticleManager:DestroyParticle(glowParticle, true);
    glowParticle = nil;
  end
end

function createGlowParticle(owningEntity)
  local modelAttachmentIndex = owningEntity:ScriptLookupAttachment("flashlight_beam");
  local vecStartPos = owningEntity:GetAttachmentOrigin(modelAttachmentIndex);
  local direction = -owningEntity:GetForwardVector();
  local vecEndPos = vecStartPos + (direction * 140);
  local glowParticleName = "particles/tool_fx/flashlight_thirdperson.vpcf";
  glowParticle = ParticleManager:CreateParticle(glowParticleName, PATTACH_POINT_FOLLOW, owningEntity);
  ParticleManager:SetParticleControlEnt(glowParticle, 1, owningEntity, PATTACH_POINT_FOLLOW, "flashlight_beam", Vector(0, 0, 0), true);
  ParticleManager:SetParticleControl(glowParticle, 2, vecEndPos);
  ParticleManager:SetParticleControl(glowParticle, 5, Vector(lightColors[lightColorsIndex][1], lightColors[lightColorsIndex][2], lightColors[lightColorsIndex][3]));
end

function FlashlightThink()
  if (flashlightOn) then
    local owningEntity = thisEntity;
    if (isEquipped) then
      owningEntity = handAttachment;
    end
    local modelAttachmentIndex = owningEntity:ScriptLookupAttachment("flashlight_beam");
    local vecStartPos = owningEntity:GetAttachmentOrigin(modelAttachmentIndex);
    local direction = -owningEntity:GetForwardVector();
    local vecEndPos = vecStartPos + (direction * 140);
    ParticleManager:SetParticleControlEnt(glowParticle, 1, owningEntity, PATTACH_POINT_FOLLOW, "flashlight_beam", Vector(0, 0, 0), true);
    ParticleManager:SetParticleControl(glowParticle, 2, vecEndPos);
  end
  return 0.01;
end