# Knockback function

15 replies__1__

16.09.19 10:48:01 am

Hold on! I did search the forum, all I found were complete scripts for different purposes that don't work as I intend.

They either used arrays, that I don't want or they had hard to configure (or bad) weapon system.

They also didn't let me add more than just weapons very easily.

Hello!

I'm in the lookout for a function that receives the following parameters:

It will knock back the player

That's all I need, I can (probably) make the rest of the calculations alone.

Note: It shouldn't let a player enter somewhere he can't get out of.

Note: It should be efficient (no arrays please).

Note: Distance should be in pixels, of course.

Thank you!

They either used arrays, that I don't want or they had hard to configure (or bad) weapon system.

They also didn't let me add more than just weapons very easily.

Hello!

I'm in the lookout for a function that receives the following parameters:

(p, angle, distance)

It will knock back the player

p

to the distance distance

using the angle angle

.That's all I need, I can (probably) make the rest of the calculations alone.

Note: It shouldn't let a player enter somewhere he can't get out of.

Note: It should be efficient (no arrays please).

Note: Distance should be in pixels, of course.

Thank you!

fish

For simple implementation, assume the player is at pixel coordinates (px,py). Use setpos to set the player's position to (px+distance*cos(angle), py+distance*sin(angle)). However, if you don't want the player to be pushed, say, inside a wall, then you should do ray tracing method, for example (pseudocode):

Set the step value s to not too small or not too big (like distance/10) will achieve correct result with good performance.

Code:

1

2

3

4

5

6

7

8

9

10

11

2

3

4

5

6

7

8

9

10

11

dir := normalize(cos(angle), sin(angle))

final_target := (px, py)

for t from 0 to distance step by s:

tentative_target := (px,py) + dir * t

if tile at tentative_target is walkable:

final_target := tentative_target

else:

break

setpos(p, final_target)

final_target := (px, py)

for t from 0 to distance step by s:

tentative_target := (px,py) + dir * t

if tile at tentative_target is walkable:

final_target := tentative_target

else:

break

setpos(p, final_target)

Set the step value s to not too small or not too big (like distance/10) will achieve correct result with good performance.

edited 2×, last 17.09.19 01:06:24 pm

It seems to be good.

**Mami Tomoe has written:**

That is Lua right...?

No, it's not. That is a piece of pseudo code to demonstrate the algorithm. You said you can do the rest of the calculations alone so I thought you can implement it in Lua by yourself.

It seems to be good.

I program in C# primarily, I don't know what a "pseudo" is.

I meant if you give me the function in Lua, I can make use of it from there.

I don't need weapon config or the other stuff that people usually post.

I meant if you give me the function in Lua, I can make use of it from there.

I don't need weapon config or the other stuff that people usually post.

fish

Code:

1

2

3

4

5

6

7

8

2

3

4

5

6

7

8

local function knockback(p, angle, distance)

local x, y = get_player(p, 'x'), get_player(p, 'y')

local new_x, new_y = x + distance * math_cos(angle), y + distance * math_sin(angle)

if tile(math_ceil(new_x / 32), math_ceil(new_y / 32), 'walkable') then

exec('setpos ' .. p .. ' ' .. new_x .. ' ' .. new_y)

end

end

local x, y = get_player(p, 'x'), get_player(p, 'y')

local new_x, new_y = x + distance * math_cos(angle), y + distance * math_sin(angle)

if tile(math_ceil(new_x / 32), math_ceil(new_y / 32), 'walkable') then

exec('setpos ' .. p .. ' ' .. new_x .. ' ' .. new_y)

end

end

I've created this, is there any better way of doing it?

The

if

line I mean.@ Gaios: Pay attention to what I need above, those threads/files provide inefficient and overkill scripts, some even being outdated.

fish

This is near correct, but If the tile is not walkable, the player won't be knocked back at all. I think you'd like to have the player pushed to the edge of the unwalkable tile.

It seems to be good.

Do you know a good way of doing it? I tried using a while loop but it was quite messy.

First the game froze in an infinite loop, then it made it possible to go over walls...

It was that point I decided to give up until I have to do it alone or someone can help.

First the game froze in an infinite loop, then it made it possible to go over walls...

It was that point I decided to give up until I have to do it alone or someone can help.

fish

@ Mami Tomoe: You need to do some precision, eg. each 5px.

This is some stuff that I use:

This may be optimized to local vars eg.

This is some stuff that I use:

Code:

1

2

3

4

5

6

7

8

9

2

3

4

5

6

7

8

9

function pos_trigger(x, y, rot, power)

rot = (rot < -90) and rot + 360 or rot

local angle = math.rad(math.abs(rot + 90)) - math.pi

local new_x = math.floor((x + math.cos(angle) * power))

local new_y = math.floor((y + math.sin(angle) * power))

return new_x, new_y

end

rot = (rot < -90) and rot + 360 or rot

local angle = math.rad(math.abs(rot + 90)) - math.pi

local new_x = math.floor((x + math.cos(angle) * power))

local new_y = math.floor((y + math.sin(angle) * power))

return new_x, new_y

end

This may be optimized to local vars eg.

local floor = math.floor

but in global scope. @ Gaios: I don't exactly understand what your function is used for...

EDIT:

Okay, now I get it.

Nice code! With a bit of tinkering I got it to a 95% perfection state!

One problem though...

This area is not walk-able, as you can see the bot can't get out:

But in the console I get this:

EDIT:

Okay, now I get it.

Nice code! With a bit of tinkering I got it to a 95% perfection state!

Code:

1

2

3

4

5

6

7

8

9

10

11

12

13

2

3

4

5

6

7

8

9

10

11

12

13

local function knockback(p, rot, power)

local x, y = get_player(p, 'x'), get_player(p, 'y')

rot = (rot < -90) and rot + 360 or rot

local angle = math_rad(math_abs(rot + 90)) - math_pi

local new_x = math_floor((x + math_cos(angle) * power))

local new_y = math_floor((y + math_sin(angle) * power))

if tile(math_floor(new_x / 32), math_floor(new_y / 32), 'walkable') then

exec('setpos ' .. p .. ' ' .. new_x .. ' ' .. new_y)

end

end

local x, y = get_player(p, 'x'), get_player(p, 'y')

rot = (rot < -90) and rot + 360 or rot

local angle = math_rad(math_abs(rot + 90)) - math_pi

local new_x = math_floor((x + math_cos(angle) * power))

local new_y = math_floor((y + math_sin(angle) * power))

if tile(math_floor(new_x / 32), math_floor(new_y / 32), 'walkable') then

exec('setpos ' .. p .. ' ' .. new_x .. ' ' .. new_y)

end

end

One problem though...

This area is not walk-able, as you can see the bot can't get out:

But in the console I get this:

edited 1×, last 18.09.19 12:40:34 am

fish

@ Gaios: thanks it works now.

EDIT:

I've come across a problem where a power above 32~ tiles will make the player skip the wall, which can result in no-clipping outside of the map.

Is there a good fix for that?

EDIT:

I've come across a problem where a power above 32~ tiles will make the player skip the wall, which can result in no-clipping outside of the map.

Is there a good fix for that?

edited 1×, last 21.09.19 07:44:12 pm

fish

@ Mami Tomoe: If we assume that

power

won't be greater than 60 then just divide the power by 2 and do double check for normal power and divided one.__1__