Speculative CCD without rigidbody

Questions & Answers
1

I am making bullet physics through script without rigidbody using raycast and I wanna know how to implement Speculative CCD for it because bullets keep passing through at high speeds.

this is my bullet script

public class C_BaseKinematicEntity : MonoBehaviour
{
    public C_BaseKinematicEntity(GameObject entity, EntityProperties_t entityProperties)
    {
        this.entity = entity;
        this.mass = entityProperties.mass;
        this.drag = entityProperties.drag;
        this.angularDrag = entityProperties.angularDrag;
    }

    public GameObject entity;
    public float drag, angularDrag, mass;
    public Vector3 position, velocity, angularVelocity;
    public Quaternion rotation;

    public void Setup(EntityData_t entityData)
    {
        this.position = entityData.position;
        this.rotation = entityData.rotation;
        this.velocity = entityData.velocity;
        this.angularVelocity = entityData.angularVelocity;

        this.UpdateGameObject();
    }

    public void UpdateGameObject()
    {
        this.entity.transform.position = this.position;
        this.entity.transform.rotation = this.rotation;
    }
    public void UpdateVelocity()
    {
        this.velocity += Physics.gravity * Time.fixedDeltaTime;
        this.velocity *= (1 - Time.fixedDeltaTime * this.drag);

        Util.Render.DebugCube(this.position + this.velocity, 0.1f, Color.grey);
    }
    public void UpdatePosition()
    {
        this.position += this.velocity * Time.fixedDeltaTime;
    }
    public void UpdateRotation()
    {
        this.rotation = Quaternion.FromToRotation(Vector3.forward, this.velocity);
    }
    public void UpdateCollision()
    {
        float maxDistance = this.velocity.magnitude * Time.fixedDeltaTime;

        RaycastHit hit;

        if (Physics.BoxCast(this.entity.transform.position, this.entity.transform.lossyScale / 2, this.entity.transform.forward, out hit, this.entity.transform.rotation, maxDistance))
        {
            ProcessCollision(hit);
        }
    }
    public virtual void ProcessCollision(RaycastHit hit) { }
}
2

You can take the current bullet position, the previous bullet position, and call Physics.RaycastAll() or Physics.SphereCastAll() between both positions. That would give you all objects the bullet has passed through in that timestep.