Collisions, bullet, multicollisions , distance to enemy etc

Questions
#1

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I have a main character (player), he has 2 collisions.
1 his body that collects coins and reacts to enemy touch
2 circle of his perception, if the enemy touches the circle of perception, then he understands its angle, and creates a bullet flying into it

Coin
Has a collision with trigger type. Removed when the player’s body touches it but not the circle of perception

Enemy
Has body collision
Does not react to coins and the circle of perception, but if it touches with a bullet, it is removed. When it dies, it creates a coin.

How it is possible to implement it and not to mix collisions?

Is it possible to get the distance to an object without the help of collisions? when the distance with the enemy is less than 10 - a bullet is created?

Tell me how to implement a bullet hell game.
Does it make sense to use so many collisions?
How to correctly refer to the created object from the object that did not create it?

#2

You need to add more groups so that you’re able to tell them apart!

#3

circle of perception is trigger , is it possible to get collision point from it?

#4

No. You need to change to kinematic or calculate it yourself

#5

circle of perception should not block the passage for the enemy.

#6

I use a helper module with some basics maths functions.

For distance between two points :

function dist_xy(x1,y1, x2,y2)
    return ((x2-x1)^2+(y2-y1)^2)^0.5
end

Or you can use vmath.length() API reference (vmath)
You just need to calculate the vector between the two positions you’re interested in then get its length.

I’m not sure which one would be the most efficient. If critical it would be better to do some benchmark.

Hope that helps.
I’m not the greatest neither in Defold, nor in Lua.

#7

I thought about it, but it seemed to me that I could push off from the capabilities of the physics engine.
Thank you.

#8

It doesn’t have to if you don’t want it to! From your original post I’d create the following collision objects and assign them these groups and masks:

Player

  • Body - Collects coins and reacts to enemy touch
    • Group: PLAYER
    • Mask: ENEMY, COIN
  • Circle of perception - Detects nearby enemies
    • Group: ENEMY_DETECTOR
    • Mask: ENEMY

Enemy

  • Body - For collisions with player and bullets. Does not react to coins and circle of perception.
    • Group: ENEMY
    • Mask: PLAYER, BULLET, ENEMY_DETECTOR

In your player collision code you check if a collision happened with the “body” or “circle of perception”:

function on_message(self, message_id, message, sender)
	if message_id == hash("contact_point_response") then
		if message.other_group == hash("ENEMY") and message.own_group == hash("PLAYER") then
			print("Owww! That hurts!")
		elseif message.other_group == hash("ENEMY") and message.own_group == hash("ENEMY_DETECTOR") then
			print("Enemy nearby! Fire bullet!")
			local enemy_pos = go.get_position(message.other_id)
		end
	end
end
3 Likes
#9

Thanks!!!