Esempio n. 1
0
        public static QuadraticResult QuadraticEquation(float a, float b, float c)
        {
            QuadraticResult retval = new QuadraticResult();

            float b4ac = b * b - 4 * a * c;

            if (b4ac < 0)
            {
                retval.numResults = 0;
            }
            else if (b4ac == 0)
            {
                //Mathf.Sqrt(0) is 0 so ignore it
                retval.numResults = 1;
                retval.r1         = -b / (2 * a);
            }
            else
            {
                float sq = Mathf.Sqrt(b4ac);
                retval.numResults = 2;
                retval.r1         = (-b + sq) / (2 * a);
                retval.r2         = (-b - sq) / (2 * a);
            }

            return(retval);
        }
        /*
         * Calc time to intersect of linear moving target, given intial positions and known speed
         */
        public static float CalcIntersectTime(Vector3 enemyPos, Vector3 enemyVelocity, Vector3 firingPos, float bulletSpeed)
        {
            //using the expanding sphere vs growing line method
            //http://playtechs.blogspot.kr/2007/04/aiming-at-moving-target.html

            //make local, sphere is now at origin
            Vector3 dif = enemyPos - firingPos;

            //squared speed dif
            float a = bulletSpeed * bulletSpeed - Vector3.Dot(enemyVelocity, enemyVelocity);

            //two times dot of our vector and the escape vel
            float b = -2 * Vector3.Dot(enemyVelocity, dif);

            float c = -Vector3.Dot(dif, dif);

            QuadraticResult res = UTIL.QuadraticEquation(a, b, c);

            switch (res.numResults)
            {
            case 1:
                if (res.r1 > 0)
                {
                    return(res.r1);
                }
                break;

            case 2:
                float max = Mathf.Max(res.r1, res.r2);

                if (max > 0)
                {
                    return(max);
                }
                break;

            default:
                break;
            }
            return(Mathf.Infinity);
        }