Shows the licence plate of the car in front

LicencePlateDisplay_Raycast.cs

/*
 * Raycast version
 */
using System;
using GTA;
using GTA.Math;
using GTA.Native;

public class Raycast : Script
{
    public Raycast()
    {
        Tick += OnTick;
    }

    void OnTick(object sender, EventArgs e)
    {
        Ped player = Game.Player.Character;
        if (!player.IsInVehicle())
        {
            return;
        }
        Vehicle vehicle = player.CurrentVehicle;
        float searchdist = 30.0f;
        Vector3 vehPos = vehicle.Position;
        Vector3 vehDir = vehicle.ForwardVector;
        Vector3 vehFor = vehPos + (vehDir * searchdist);
        int ray = Function.Call<int>(Hash._CAST_RAY_POINT_TO_POINT, vehPos.X, vehPos.Y, vehPos.Z, vehFor.X, vehFor.Y, vehFor.Z, 10, vehicle, 7);

        OutputArgument hit = new OutputArgument();
        OutputArgument endcoords = new OutputArgument();
        OutputArgument surfacenormal = new OutputArgument();
        OutputArgument entityHit = new OutputArgument();
        Function.Call(Hash._GET_RAYCAST_RESULT, ray, hit, endcoords, surfacenormal, entityHit);
        Vehicle hitVehicle = entityHit.GetResult<Vehicle>();
        Vector3 hitVehPos = hitVehicle.Position;

        OutputArgument x = new OutputArgument();
        OutputArgument y = new OutputArgument();
        bool success = Function.Call<bool>(Hash._WORLD3D_TO_SCREEN2D, hitVehPos.X, hitVehPos.Y, hitVehPos.Z, x, y);
        if (success && hitVehicle.Exists())
        {
            string name = hitVehicle.FriendlyName;
            string numplate = hitVehicle.NumberPlate;
            string text = "^\n" + name + "\n" + numplate + "\n";

            Function.Call(Hash.SET_TEXT_FONT, 0);
            Function.Call(Hash.SET_TEXT_SCALE, 0.2, 0.2);
            Function.Call(Hash.SET_TEXT_COLOUR, 255, 255, 255, 255);
            Function.Call(Hash.SET_TEXT_WRAP, 0.0, 1.0);
            Function.Call(Hash.SET_TEXT_CENTRE, 0);
            Function.Call(Hash.SET_TEXT_DROPSHADOW, 0, 0, 0, 0, 0);
            Function.Call(Hash.SET_TEXT_EDGE, 1, 0, 0, 0, 205);
            Function.Call(Hash._SET_TEXT_ENTRY, "STRING");
            Function.Call(Hash._ADD_TEXT_COMPONENT_STRING, text);
            Function.Call(Hash._DRAW_TEXT, x.GetResult<float>(), y.GetResult<float>());
            Function.Call(Hash.DRAW_RECT, x.GetResult<float>() + 0.027f, y.GetResult<float>() + 0.043f, 0.058f, 0.056f,
                75, 75, 75, 175);
        }
    }
}

LicencePlateDisplay_Search.cs

/*
 * Search version
 * Due to having multiple entries we can do fancy stuff like fade-in,
 * fade-out, depending on distance, and showing multiple boxes.
 */

using System;
using System.CodeDom.Compiler;
using GTA;
using GTA.Math;
using GTA.Native;

public class SearchCone : Script
{
    public SearchCone()
    {
        Tick += OnTick;
    }

    private bool active = false;
    private Vehicle lastVehicle;

    bool areTheseClose(float h1, float h2, float separation)
    {
        var diff = Math.Abs(h1 - h2);
        if (diff < separation)
            return true;
        if (Math.Abs(diff - 360) < separation)
            return true;

        return false;
    }

    float howClose(float h1, float h2, float separation)
    {
        var diff = Math.Abs(h1 - h2);
        if (diff < separation)
            return (separation - diff) / separation;
        if (Math.Abs(diff - 360) < separation)
            return (separation - Math.Abs(diff - 360)) / separation;

        return 0.0f;
    }

    void OnTick(object sender, EventArgs e)
    {
        Ped player = Game.Player.Character;
        Vehicle vehicle;
        if (!player.IsInVehicle())
        {
            vehicle = lastVehicle;
        }
        else
        {
            vehicle = player.CurrentVehicle;
            lastVehicle = vehicle;
        }

        if (vehicle == null)
            return;

        if (Game.IsControlJustPressed(0, Control.VehicleHandbrake))
        {
            active = !active;
            UI.Notify("Plate viewer " + (active ? "enabled" : "disabled"));
        }

        if (!active)
        {
            return;
        }

        Vector3 vehPos = vehicle.Position;

        const float searchDist = 30.0f;

        Vehicle[] vehicles = World.GetAllVehicles();

        for (int i = 0; i < vehicles.Length; i++)
        {
            if (vehicles[i] != vehicle)
            {
                Vector3 targetPos = vehicles[i].Position;

                Vector3 direction = targetPos - vehPos;
                direction.Normalize();
                float vehDirection = Convert.ToSingle(Math.Atan2(direction.Y, direction.X) * (180.0f / Math.PI));
                float myHeading = (vehicle.Heading + 90.0f) % 360;

                OutputArgument x = new OutputArgument();
                OutputArgument y = new OutputArgument();
                bool success = Function.Call<bool>(Hash._WORLD3D_TO_SCREEN2D, targetPos.X, targetPos.Y, targetPos.Z, x, y);
                bool close = areTheseClose(vehDirection, myHeading, 30.0f);
                float centerCloseness = howClose(vehDirection, myHeading, 30.0f);
                if (success && close)
                {
                    float dist = World.GetDistance(vehPos, targetPos);
                    if (dist < searchDist)
                    {
                        float meCloseness = (float)Math.Pow(2.0f * (searchDist - dist) / searchDist, 2.0f);
                        int drawAlpha = Math.Min((int)(255 * centerCloseness * meCloseness), 255);
                        string name = vehicles[i].FriendlyName;
                        string numplate = vehicles[i].NumberPlate;

                        string text = "^\n" + name + "\n" + numplate + "\n";
                        float screenX = x.GetResult<float>();
                        float screenY = y.GetResult<float>();
                        ShowVehicleTag(text, screenX, screenY, drawAlpha);
                    }
                }
            }
        }
    }

    private static void ShowVehicleTag(string text, float x, float y, int alpha)
    {
        Function.Call(Hash.SET_TEXT_FONT, 0);
        Function.Call(Hash.SET_TEXT_SCALE, 0.4, 0.4);
        Function.Call(Hash.SET_TEXT_COLOUR, 255, 255, 255, alpha);
        Function.Call(Hash.SET_TEXT_WRAP, 0.0, 1.0);
        Function.Call(Hash.SET_TEXT_CENTRE, 0);
        Function.Call(Hash.SET_TEXT_DROPSHADOW, 0, 0, 0, 0, 0);
        Function.Call(Hash.SET_TEXT_EDGE, 1, 0, 0, 0, 205);
        Function.Call(Hash._SET_TEXT_ENTRY, "STRING");
        Function.Call(Hash._ADD_TEXT_COMPONENT_STRING, text);
        Function.Call(Hash._DRAW_TEXT, x, y);
        Function.Call(Hash.DRAW_RECT, x + 0.03f, y + 0.057f, 0.07f, 0.06f, 75, 75, 75, alpha / 2);
    }


}