Weapons / Multiple Enemies / ** Now Bullets **

[ninwa]

You're almost there!

Take a look at this:

Code: Select all

for i=1, #enemies do
   if not CheckCollision(player, enemies[i]) then
       -- the vector from enemy to the player
       local vx = player.x - enemies[i].x
       local vy = player.y - enemies[i].y

       -- normalize it, i.e. divide it by it's length
       local length = math.sqrt(vx * vx + vy * vy)
       vx = vx / length
       vy = vy / length

       -- move the zombie towards the player
       enemies[i].x = enemies[i].x + vx * enemies[i].speed * dt
       enemies[i].y = enemies[i].y + vy * enemies[i].speed * dt
   end
end

[Ryne]

Ahh, now I see what I was doing wrong. I actually had my function worded EXACTLY like you have it, though I didn't add the iterator, thinking it wasn't needed. Thanks again!

EDIT: Holy Awesome! it works perfectly. I'm going to fix up a lot of my code and actually submit a playable demo. Thanks Ninwa!

[Ryne]

Alright so everything worked great for multiple enemies FOLLOWING the player. The only issue now is that when I try to use the same method to change player direction it only works for the last enemy drawn. Here is my function to change "enemies.dir" depending on where the enemy is in relation to the player.

Function:

Code: Select all

function CheckDirection(obj1, obj2)

	if obj1.x > obj2.x + obj2.w - 1 then
	for i=1, #enemies do
	enemies[i].dir = "right"
	end
	
	elseif obj1.y > obj2.y + obj2.h - 1 then
	for i=1, #enemies do
	enemies[i].dir = "down"
	end
	
	elseif obj2.x > obj1.x + obj1.w - 1 then
	for i=1, #enemies do
	enemies[i].dir = "left"
	end

	elseif obj2.y > obj1.y + obj1.h - 1 then
	for i=1, #enemies do
	enemies[i].dir = "up"
	end
	end

end

Then for checking I use:

Code: Select all

	for i=1, #enemies do
	CheckDirection(player, enemies[i])
	end

And here is the .love to illustrate what is happening.
http://dl.dropbox.com/u/7905642/lz_01.love

Any ideas?

[TechnoCat]

http://dl.dropbox.com/u/7905642/lz_01.love

dt is your friend! He is flying way fast out of control on my computer.

Code: Select all

	-- keys
  	if love.keyboard.isDown( "w" ) then
	direction = "up"
	state = anim.walkup
	player.y = player.y - 1

should be

Code: Select all

player.y = player.y - 1*dt

Alright so everything worked great for multiple enemies FOLLOWING the player. The only issue now is that when I try to use the same method to change player direction it only works for the last enemy drawn. Here is my function to change "enemies.dir" depending on where the enemy is in relation to the player.
Any ideas?

This is because you are doing it for each zombie in the list, therefore only the last zombie direction is kept for the draw. He can't possibly face them all at the same time if they are different unit vectors from the player.

What you need to do is iterate over the zombies to find the nearest one, and then face that one.
Sorry, in advance for psuedo-code

Code: Select all

closestZombie = zombies[1]
for i,v in zombies do
  if v.distanceFromPlayer() < closestZombie.distanceFromPlayer() then
    closestZombie = v
end
--now set your player facing closestZombie

When you exit that for loop, closestZombie should be assigned to the closest one. Just make sure you catch cases where there are no zombies, or if the zombies aren't yet close enough to bother making the player turn around.

Distance formula for 2 2d points would be

Code: Select all

-- First point is (x1,y1)
-- Second point is (x2, y2)
distance = math.sqrt((x2-x1)^2+(y2-y1)^2)

[Ryne]

Thanks for the reply but I don't think you understand my question. I don't want the player to face the zombie. The player has nothing to do with my question.

Right now each enemy spawned has a "dir" variable for direction. It can be up, down, left, or right. I have a function that SHOULD change each of the enemies "dir" value depending on their position in relevance to the player. Right now it only changes that value for the LAST enemy thats spawned.

Also I have to use player.x = player.x + 50 * dt, in order to get it to the same speed as "1" without DT. This seems to make the player lag/jitter.

[nevon]

Also I have to use player.x = player.x + 50 * dt, in order to get it to the same speed as "1" without DT. This seems to make the player lag/jitter.

That's because dt is the time passed since the last update. Usually it's a very small number. So if you multiply dt by 50, that means your player will move 50px in one second. If you just put 1 (without multiplying it by dt) it's going to move much faster on a fast machine than it will on a slow one.

[Ryne]

Also I have to use player.x = player.x + 50 * dt, in order to get it to the same speed as "1" without DT. This seems to make the player lag/jitter.

That's because dt is the time passed since the last update. Usually it's a very small number. So if you multiply dt by 50, that means your player will move 50px in one second. If you just put 1 (without multiplying it by dt) it's going to move much faster on a fast machine than it will on a slow one.

Ahh, I've set it to 60, which is my refresh rate and it is back to perfectly smooth. Anything besides 60 looks fine but its a little jittery.

[TechnoCat]

Ahh, I've set it to 60, which is my refresh rate and it is back to perfectly smooth. Anything besides 60 looks fine but its a little jittery.

Possibly try math.floor'ing the x and y draw position values.

[Ryne]

Alright my thread is being diverted. I still need help with this:

Thanks for the reply but I don't think you understand my question. I don't want the player to face the zombie. The player has nothing to do with my question.

Right now each enemy spawned has a "dir" variable for direction. It can be up, down, left, or right. I have a function that SHOULD change each of the enemies "dir" value depending on their position in relevance to the player. Right now it only changes that value for the LAST enemy thats spawned.

And here is my post again:

Function:

Code: Select all

function CheckDirection(obj1, obj2)

	if obj1.x > obj2.x + obj2.w - 1 then
	for i=1, #enemies do
	enemies[i].dir = "right"
	end
	
	elseif obj1.y > obj2.y + obj2.h - 1 then
	for i=1, #enemies do
	enemies[i].dir = "down"
	end
	
	elseif obj2.x > obj1.x + obj1.w - 1 then
	for i=1, #enemies do
	enemies[i].dir = "left"
	end

	elseif obj2.y > obj1.y + obj1.h - 1 then
	for i=1, #enemies do
	enemies[i].dir = "up"
	end
	end

end

Then for checking I use:

Code: Select all

	for i=1, #enemies do
	CheckDirection(player, enemies[i])
	end

And here is the .love to illustrate what is happening.
http://dl.dropbox.com/u/7905642/lz_01.love

Any ideas?

[TechnoCat]

Code: Select all

function CheckDirection(obj1, obj2)
  if obj1.x > obj2.x + obj2.w - 1 then
    for i=1, #enemies do
      enemies[i].dir = "right"
    end
....

If you are checking between obj1 and obj2, then why are you invoking every zombie in the table and changing their direction?
Seems like it should be something more like:

Code: Select all

function CheckDirection(obj1, obj2)
  if obj1.x > obj2.x + obj2.w - 1 then
    obj2.dir = "right"
....

And you NEED dt (or some way to time frames). The guy moves at the speed of light on my computer because it is computation based instead of time based.