-- EDITABLE (NO RECOMMENDED)
parts = 10 						-- amount of sides that is displayed behind the vehicle (you can see the corners)
partLength = 1 					-- length of every part in SA coördinates
lineThickness = 15 				-- thickness of every line (not sure about the unit)
xOff, yOff, zOff = 0, -2.5, 0 	-- offset of the rainbow
fadeLength = 5 					-- amount of parts from the end to the front that's in the fade, for some reason it starts bugging when you make it larger than 5

colors = { 						-- colors in the rainbow in RGB
	{ 255, 0, 0 },
	{ 255, 150, 0 },
	{ 255, 255, 0 },
	{ 50, 255, 0 },
	{ 0, 150, 255 },
	{ 100, 50, 255 }
		}

-- DO NOT EDIT ANYTHING BELOW HERE, UNLESS YOU KNOW WHAT YOU'RE DOING
lineOffsetZMultiplier = 0.01
vehicleTable = {}
oldPosTable = {}
partsTable = {}
if fadeLength >= parts then
	fadeLength = parts - 1
end
startFade = parts - fadeLength
fadeIndex = 255 / fadeLength
lineOffsetZ = lineThickness * lineOffsetZMultiplier



lineStartZ = zOff + #colors * lineOffsetZ * 0.5

function render ()
	for i, v in pairs ( getElementsByType ( "vehicle" ) ) do
		if not vehicleTable[v] then
			vehicleTable[v] = {}
		else
			local vx, vy, vz = getElementPosition ( v )
			
			local matrix = getElementMatrix ( v )
			local x = xOff * matrix[1][1] + yOff * matrix[2][1] + zOff * matrix[3][1] + 1 * matrix[4][1]
			local y = xOff * matrix[1][2] + yOff * matrix[2][2] + zOff * matrix[3][2] + 1 * matrix[4][2]
			local z = xOff * matrix[1][3] + yOff * matrix[2][3] + zOff * matrix[3][3] + 1 * matrix[4][3]
			
			if oldPosTable[v] then
				local oldX, oldY, oldZ = unpack ( oldPosTable[v] )
				if getDistanceBetweenPoints3D ( x, y, z, oldX, oldY, oldZ ) > partLength then
					table.insert ( vehicleTable[v], { oldX, oldY, oldZ, x, y, z } )
					oldPosTable[v] = { x, y, z }
				end
				
				for i, part in pairs ( vehicleTable[v] ) do
					if #vehicleTable[v] <= parts or i >= #vehicleTable[v] - parts then
						local a = 255
						if i < #vehicleTable[v] - parts + fadeLength then
							local index = i - ( #vehicleTable[v] - parts )
							a = 255 * fadeIndex * ( fadeLength - index )
						end
						local px1, py1, pz1, px2, py2, pz2 = unpack ( part )
						drawRainbow ( px1, py1, pz1, px2, py2, pz2, a )
					end
				end
				
				drawRainbow ( x, y, z, oldX, oldY, oldZ, 255 )
			else
				oldPosTable[v] = { x, y, z }
			end
		end
	end
end
addEventHandler ( "onClientRender", getRootElement(), render )

function drawRainbow ( x1, y1, z1, x2, y2, z2, alpha )
	for i, color in pairs ( colors ) do
		local i = #colors - i
		local r, g, b = unpack ( color )
		local z1 = z1 + - lineStartZ + ( i - 1 ) *  lineOffsetZ
		local z2 = z2 + - lineStartZ + ( i - 1 ) *  lineOffsetZ
		dxDrawLine3D ( x1, y1, z1, x2, y2, z2, tocolor(r, g, b, alpha), lineThickness )
	end
end