Nyancars script by Puma for MTA

-- 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