From 40aa4813f3faec2f5dd1c77daf66632b989f1a6b Mon Sep 17 00:00:00 2001
From: Steve <5084958+Stooberton@users.noreply.github.com>
Date: Thu, 16 May 2024 17:02:39 -0500
Subject: [PATCH] Added ACF.getTraceDepth

(Untested code)
Returns the depth in mm a trace penetrates a prop before hitting something else. This is the full line of sight thickness if there are no obstacles.
---
 lua/acf/core/utilities/traces_sh.lua | 81 ++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)

diff --git a/lua/acf/core/utilities/traces_sh.lua b/lua/acf/core/utilities/traces_sh.lua
index 25d70022d..ec7764f91 100644
--- a/lua/acf/core/utilities/traces_sh.lua
+++ b/lua/acf/core/utilities/traces_sh.lua
@@ -33,6 +33,7 @@ do -- ACF.trace
 	-- Automatically filters out and retries when hitting a clipped portion of a prop
 	-- Does NOT modify the original filter
 	local util = util
+	local sqrt = math.sqrt
 
 	local function doRecursiveTrace(traceData)
 		local Output = traceData.output
@@ -79,4 +80,84 @@ do -- ACF.trace
 
 		return Output
 	end
+
+	local function findOtherSideOfSphere(point, dir, ent)
+		local radius = ent:Radius()
+		local center = ent:GetPos()
+
+		local displacement = point - origin
+
+		local ie     = ray:Dot(displacement)^2 - displacement:LengthSqr()
+		local exit   = ray:Dot(point - center) + sqrt(ie)
+		local length = (point - exit):Length() * 25.4
+
+		return exit, length
+	end
+
+	local function findOtherSideOfPoly(Ent, Origin, Dir)
+		local Mesh = Ent:GetPhysicsObject():GetMeshConvexes()
+		local Min  = math.huge
+
+		for K in pairs(Mesh) do -- Loop over mesh
+			local Hull = Mesh[K]
+
+			for I = 1, #Hull, 3 do -- Loop over each tri (groups of 3)
+				-- Points on tri
+				local P1     = Ent:LocalToWorld(Hull[I].pos)
+				local P2     = Ent:LocalToWorld(Hull[I + 1].pos)
+				local P3     = Ent:LocalToWorld(Hull[I + 2].pos)
+
+				-- Two edges to test with
+				local Edge1  = P2 - P1
+				local Edge2  = P3 - P1
+
+				-- Plane facing the wrong way?
+				if Dir:Dot(Edge1:Cross(Edge2)) > 0 then  continue end
+
+				-- Ray is perpendicular to plane?
+				local H = Dir:Cross(Edge2)
+				local A = Edge1:Dot(H)
+
+				if A > -0.0001 and A < 0.0001 then continue end
+
+				-- Ray passes through the triangle?
+				local F = 1 / A
+				local S = Origin - P1 -- Displacement from to origin from P1
+				local U = F * S:Dot(H)
+
+				if U < 0 or U > 1 then continue end
+
+				local Q = S:Cross(Edge1)
+				local V = F * Dir:Dot(Q)
+
+				if V < 0 or U + V > 1 then continue end
+
+				-- Ray intersects triangle
+				-- Length of ray to intersection
+				local T = F * Edge2:Dot(Q)
+
+				if T > 0.0001 and T < Min then Min = T end
+			end
+		end
+
+		return Origin + Dir * Min
+	end
+
+	function ACF.getTraceDepth(trace)
+		-- Traces from the surface of an object to the furthest tri on the opposite side
+		-- Stops at any other object that is intersecting inside
+
+		local ent    = trace.Entity
+		local origin = trace.StartPos
+		local enter  = trace.HitPos
+		local rayDir = (enter - trace.StartPos):GetNormalized()
+
+		local tempFilter = {}; for k, v in pairs(trace.Filter) do filter[k] = v end -- Shallow copy of the original filter (presumably a projectile trace) prevents two overlapping cubes from infinitely intersecting
+
+		local opposite = ent._IsSpherical and findOtherSideOfSphere(enter, rayDir, ent:GetPos()) or findOtherSideOfPoly(ent, origin, rayDir)
+		local exit     = ACF.trace({start = enter, endpos = opposite, filter = tempFilter}).HitPos -- Not strictly an exit... may have run into an intersecting entity
+		local length   = (exit - enter):Length() * 25.4 -- Inches to mm
+
+		return exit, length
+	end
 end