Визуализатор "эхо". Имеет проблему с неудалением эхо после добавления, в связи с чем при большом кол-ве эхо начинает все лагать. Взято отсюда: https://facepunch.com/showthread.php?t=1440586&p=51617841&viewfull=1#post51617841

cl_echo_visualizer.lua

local echoes = {}
local echo_thickness = 10
local color_mask = Color(0,0,0,0)


local function drawStencilSphere( pos, ref, compare_func, radius, color, detail )
	render.SetStencilReferenceValue( ref )
	render.SetStencilCompareFunction( compare_func )
	render.DrawSphere(pos, radius, detail, detail, color)
end


hook.Add("PostDrawTranslucentRenderables", "Echo", function( )
	local localplayer_pos = LocalPlayer():EyePos()

	local detail = 25

	local realtime = RealTime()

	render.SetStencilEnable(true)

	render.SetStencilPassOperation( STENCILOPERATION_KEEP )
	render.SetStencilFailOperation( STENCILOPERATION_KEEP )

	for _, echo in ipairs(echoes) do
		local dist = echo.pos:Distance(localplayer_pos)

		local opacity = ((echo.radius - (dist / 2)) / echo.radius) * 0.25
		local p = (realtime - echo.start) / echo.lifetime

		if p < 1.0 and opacity > 0 then
			local outer_r = Lerp(p, 0, echo.radius)
			local inner_r = math.max(outer_r-echo_thickness,0)

			local color = echo.color
			color.a = 255 * opacity * math.pow(1-p, 2)

			render.ClearStencil()

			render.SetColorMaterial()

			render.SetStencilZFailOperation( STENCILOPERATION_REPLACE )

			drawStencilSphere(echo.pos, 2, STENCILCOMPARISONFUNCTION_ALWAYS, -outer_r, color_mask, detail ) -- big, inside-out

			render.SetStencilZFailOperation( STENCILOPERATION_INCR )

			drawStencilSphere(echo.pos, 2, STENCILCOMPARISONFUNCTION_ALWAYS, outer_r, color_mask, detail ) -- big

			render.SetStencilZFailOperation( STENCILOPERATION_INCR )

			drawStencilSphere(echo.pos, 2, STENCILCOMPARISONFUNCTION_ALWAYS, -inner_r, color_mask, detail ) -- small, inside-out

			render.SetStencilZFailOperation( STENCILOPERATION_DECR )

			drawStencilSphere(echo.pos, 2, STENCILCOMPARISONFUNCTION_ALWAYS, inner_r, color_mask, detail ) -- small

			render.SetColorMaterialIgnoreZ()

			drawStencilSphere(echo.pos, 2, STENCILCOMPARISONFUNCTION_EQUAL, -outer_r, color, detail ) -- big, inside-out
		end
	end

	render.SetStencilEnable(false)
end)

local function addEcho(time,pos,radius,color)
	local i = table.insert(echoes,{
		pos   = pos,
		start = RealTime(),
		lifetime = time,
		radius = radius,
		color = color,
	})

	timer.Simple(time,function()
		table.remove(echoes,i)
	end)
end


timer.Create("string identifiesdfar",.2,50,function()
	addEcho(20, LocalPlayer():GetPos(), 20000, Color(255,0,0))
end)

timer.Simple(20,function()
	echoes = {}
end)