CODEWITHSUNDEEP
c++2dgame-enginesfml
micnyk
micnyk

Reputation: 746

Top-down perspective aim tank turret with mouse

I want to make tank's turret be aimed with mouse in a top-down perspective. I have written some code to animate rotation to given angle:

void Tank::rotateTurret(float angle) {
    turretRotation += angle;
}

sf::Sprite turret;
void Tank::update(unsigned int time) {
    if (turretRotation != 0.0f) {
        float rotate;

        if (turretRotation > 0.0f) {
            rotate = turretRotationSpeed * time;

            if (rotate > turretRotation) {
                rotate = turretRotation;
                turretRotation = 0;
            }
            else
                turretRotation -= rotate;
        }
        else {
            rotate = -turretRotationSpeed * time;

            if (rotate < turretRotation) {
                rotate = turretRotation;
                turretRotation = 0;
            }
            else
                turretRotation -= rotate;
        }

        turret.rotate(rotate);
    }
}

And I can calculate mouse pointer angle relative to top left corner:

void TankPlayerController::update() {
    sf::Vector2i mousePosition = sf::Mouse::getPosition(*relativeWindow);
    sf::Vector2i mouseMovement = mousePosition - lastMousePosition;

    if (mouseMovement.x != 0 || mouseMovement.y != 0) {
        float mouseAngle = VectorAngleDeg(mousePosition.x, mousePosition.y);

        tank->rotateTurret(???);

        lastMousePosition = mousePosition;
    }
}

But I have no idea how to combine it together. How should it be done?

Upvotes: 0

Views: 282

Answers (1)

William Jones
William Jones

Reputation: 204

You need to calculate the angle to the center of the turret (CoT) from the upper left corner (ULHC) and the angle to the mouse location from the ULHC. Next consider the triangle formed from the lines connecting the ULHC to the CoT, the line connecting the ULHC to the mouse pointer location and the line connecting the CoT to the mouse pointer location. Since you know the distance from the ULHC to the CoT and the distance from the ULHC to the mouse pointer location all you need to do is determine the difference between the angle to the CoT and the mouse pointer position you can use the Law of Cosines to get the angel between the ULHC and the mouse position at the turret and from there the angle to any arbitrary axis you choose.

It would be easier with a picture :|

Upvotes: 1

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