JDodi/GunsAndBullets

Generic gun and bullets

Guns and Bullets

This project is a set of generic gun and bullet components to be futher expanded upon for specific projects. They are designed around my usual use case of fast moving bullets fired from vehicles.

The goal of this project was to create a sort of "canonical" version of bullet and gun code that I so frequently write and rewrite. Rather than constantly pulling and gutting code from old projects, it'd be nice to have a single package that I can just import.

This project was built in Unity 2017.3.1f1.

Download

You can either clone the repository or download the asset package located in the root.

Bullets

The bullets are handled by raycasting forwards every frame. It allows for fast moving bullets to almost never tunnel through objects. I've been reusing this exact same code for years and it has served me well.

private void MoveBullet()
{
    RaycastHit rayHit;
    Ray velocityRay = new Ray(transform.position, velocity.normalized);
    bool rayHasHit = Physics.Raycast(velocityRay, 
                                     out rayHit,
                                     velocity.magnitude * kVelocityMult * Time.deltaTime,
                                     hitMask);

    if (rayHasHit == true)
    {
        // Bullet hit something.
        // Put code here to damage the thing you hit using your components.
        DestroyBullet(rayHit.point, true);
    }
    else
    {
        // Bullet didn't hit anything, continue moving.
        transform.Translate(velocity * Time.deltaTime, Space.World);
    }
}

Limitations

The code in this project is very simple. While it is generic enough to cover what I feel is 90% of use cases involving fast bullets, there are some limitations to keep in mind.

1. This solution is designed around bullets that will be traveling at fast speeds relative to their targets. If the targets travel at similar speeds, or faster, than the bullets, then it is possible for the bullet to be skipped over in a frame.
2. Neither the bullets, nor the impact effects, are pooled. Pooling is too implementation specific to include here, so keep in mind that you may want to write a pooling system for bullets if bullet spawning/destruction becomes a bottleneck.

Guns

The guns have a couple useful features:

• Deviation can be added to make guns inaccurate. The value is the max error off boresight that a bullet can have.
• Using the Gimbal Range, guns can auto-aim to some degree. More on this below.
• Multiple barrels are supported, and can be set to fire together, or sequentially.
• Ammo usage can be toggled on/off at any time.

Gimballing

An optional feature that I often find myself repeatedly implementing is gimballing guns. The idea behind this is to allow the gun to hit a precise point without necessarily aiming the gun directly at that point. This is very useful for things such as auto-aim, AI controlled weapons, and ensuring that guns converge on a crosshair.

Gimbal Range describes how far off-boresight the gun can hit a specified target. To enable this feature, set the UseGimballedAiming property on the gun component to true. Use the TargetPosition to assign a world position for the gun to try to aim at. As long as UseGimballedAiming is true, the gun will try its best to hit TargetPosition.

Limitations

As with the bullets, I feel this component is generic enough to cover 90% of the use cases I'm interested in with little to no modification. However, there is one caveat to keep in mind.

Fire rate is handled through a cooldown variable, meaning that the gun cannot fire faster than the update loop. At 60fps, this means the practical lower limit on Fire Delay is 0.0167. At 30fps, this grows to 0.0333. For extremely fast firing guns either the code must be extended, or workarounds such as firing multiple barrels at the same time should be put in place.

Remember that bullets are not pooled. If you're running into fire rate limitations, you might want to start thinking about setting up a pooling system, as the time Unity spends doing instantiation/destruction calls would no longer be trivial.

Changelog

1.1 (Feb 20 2019)

• Fixed bug where bullet would spawn hit effect at own position rather than impact position.

1.0 (Feb 11 2019)

• Released