wnsrc/lua/pac3/core/client/parts/clip.lua

--[[
| This file was obtained through the combined efforts
| of Madbluntz & Plymouth Antiquarian Society.
|
| Credits: lifestorm, Gregory Wayne Rossel JR.,
| 	Maloy, DrPepper10 @ RIP, Atle!
|
| Visit for more: https://plymouth.thetwilightzone.ru/
--]]

local render_EnableClipping = render.EnableClipping
local render_PushCustomClipPlane = render.PushCustomClipPlane
local LocalToWorld = LocalToWorld
local IsEntity = IsEntity

local BUILDER, PART = pac.PartTemplate("base_drawable")

PART.FriendlyName = "clip"
PART.ClassName = "clip2"
PART.Groups = {'model', 'modifiers'}
PART.Icon = 'icon16/cut.png'

function PART:OnParent(part)
	if not part.AddModifier then return end
	part:AddModifier(self)


	-- this is only really for halos..
	local ent = self:GetOwner()

	if ent:IsValid() then
		function ent.pacDrawModel(ent)
			self:PreOnDraw()
			ent:DrawModel()
			self:PostOnDraw()
		end
	end
end

function PART:OnUnParent(part)
	if not part:IsValid() then return end
	if not part.RemoveModifier then return end

	part:RemoveModifier(self)
end

do
	local bclip

	function PART:PreOnDraw()
		bclip = render_EnableClipping(true)

		local pos, ang = LocalToWorld(self.Position + self.PositionOffset, self:CalcAngles(self.Angles + self.AngleOffset), self:GetBonePosition())
		local normal = ang:Forward()

		render_PushCustomClipPlane(normal, normal:Dot(pos))
	end

	local render_PopCustomClipPlane = render.PopCustomClipPlane

	function PART:PostOnDraw()
		render_PopCustomClipPlane()

		render_EnableClipping(bclip)
	end
end

BUILDER:Register()