[HELP] laser movement

[StDH]

Well as topic already say i need to help with laser movement like on this video:


as you cant see player and npc are moving with some angle and laser must move with them at some angle and speed, or otherwise it will be rocket.

and that: (me[angle] + npc[angle]) / 2 = laser[angle] -> i dont know if it is right, tell me if am i doing it wrong
i need to calculate angle + speed of laser [using sf::Sprite]

[ChronicRat]

Maybe I misunderstood, but you need to get direction? From sf::Transformable you can get direction via matrix:

    this = something sf::Transformable.
        const float* m = this->getTransform().getMatrix();
        return sf::Vector2f(m[0], m[1]);
 

[StDH]

i need to calculate the direction of laser from those two points

[ChronicRat]

Well, as i remember it is - normalize(V2 - V1).

[StDH]

thanks  i will write you if it works, but i'll try it later

[Grimshaw]

ChronicRat is right, normalize(V2 - V1) will give you the direction vector from V1 to V2.

If you want that in an angle, here's how you do it (radian): atan2(direction.y, direction.x), you can then convert to degrees if needed. :p

[StDH]

ChronicRat is right, normalize(V2 - V1) will give you the direction vector from V1 to V2.

If you want that in an angle, here's how you do it (radian): atan2(direction.y, direction.x), you can then convert to degrees if needed. :p

it looks like one of my function in npc[movable struct]:

#define toDegrees 57.32f        //(180 / 3.14)

float gameEntityMove::coordsToAngle(sf::Vector2f start, sf::Vector2f end)
{
        #pragma warning(disable : 4715) // not all control paths return a value

        if (start.x != end.x && start.y != end.y)
                return std::atan2(start.y - end.y, start.x - end.x) * toDegrees;
        else
                return -1;
}

am i right ?

[Nexus]

If you don't want to reinvent the wheel, you can also use Thor.Vectors, they provide already everything: angles, distances, normalization, ...

Computing the direction is then as simple as:

sf::Vector direction = thor::unitVector(b - a);

You usually don't want to work with angles unless you really need them, because the special cases (wraparound) are a bit annoying to handle.