71 lines
2.0 KiB
GDScript
71 lines
2.0 KiB
GDScript
extends KinematicBody
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export(NodePath) var player_node
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onready var player = get_node(player_node)
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export(NodePath) var solar_system_node
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onready var solar_system = get_node(solar_system_node)
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var bullet_scene = preload("res://Bullet.tscn")
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var bullet_velocity = 40.0
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var target
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var velocity := Vector3(0.0, 1.0, 1.0)
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func _ready():
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$ShotTimer.connect("timeout", self, "shoot_bullet")
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func _physics_process(delta):
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# Project the player's position into the future
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target = _get_future_position(
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player.get_center(),
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player.velocity - velocity
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)
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if target:
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var gravity = solar_system.get_gravitation_acceleration(global_transform.origin)
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look_at(target, gravity)
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global_transform.origin += velocity * delta
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func shoot_bullet():
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if not target:
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# Player can't be hit right now, abort
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return
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var instance = bullet_scene.instance()
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get_tree().get_root().add_child(instance)
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instance.global_transform.origin = global_transform.origin - global_transform.basis.z
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instance.velocity = velocity + (target - global_transform.origin).normalized() * bullet_velocity
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func _get_future_position(position, velocity):
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# Solution to the quadratic formula gives us the time at which the player would be hit
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# TODO: Take acceleration into account as well!
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var a = pow(velocity.x, 2) + pow(velocity.y, 2) + pow(velocity.z, 2) - pow(bullet_velocity, 2)
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var b = 2 * (velocity.x * (position.x - global_transform.origin.x)
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+ velocity.y * (position.y - global_transform.origin.y)
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+ velocity.z * (position.z - global_transform.origin.z))
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var c = pow(position.x - global_transform.origin.x, 2.0) \
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+ pow(position.y - global_transform.origin.y, 2.0) \
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+ pow(position.z - global_transform.origin.z, 2.0)
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var discriminant = pow(b, 2) - 4 * a * c
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if (discriminant < 0): return null # Can't hit the target :(
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var t1 = (-b + sqrt(discriminant)) / (2 * a)
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var t2 = (-b - sqrt(discriminant)) / (2 * a)
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# Choose the smallest positive t value
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var t = min(t1, t2)
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if t < 0: t = max(t1, t2)
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return position + t * velocity
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