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English Knockback function

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old Knockback function

Mami Tomoe
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Quote
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:
(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!

old Re: Knockback function

uaiek
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Quote
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):

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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)

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

old Re: Knockback function

uaiek
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Quote
user 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.

old Re: Knockback function

Mami Tomoe
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Quote
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.

old Re: Knockback function

Mami Tomoe
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Quote
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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

I've created this, is there any better way of doing it?
The 
if
line I mean.

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Pay attention to what I need above, those threads/files provide inefficient and overkill scripts, some even being outdated.

old Re: Knockback function

uaiek
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Quote
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.

old Re: Knockback function

Mami Tomoe
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Quote
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.

old Re: Knockback function

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

This is some stuff that I use:
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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
This may be optimized to local vars eg. 
local floor = math.floor
but in global scope.

old Re: Knockback function

Mami Tomoe
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Quote
@user 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!

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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

One problem though...

This area is not walk-able, as you can see the bot can't get out:
IMG:https://i.imgur.com/uDTBdN0.png


But in the console I get this:
IMG:https://i.imgur.com/wLg4MZo.png
edited 1×, last 18.09.19 12:40:34 am

old Re: Knockback function

Mami Tomoe
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Quote
@user 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?
edited 1×, last 21.09.19 07:44:12 pm

old Re: Knockback function

Gaios
Reviewer Off Offline

Quote
@user 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.
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