How are random encounters scripted?

[wjannsz]

Hi all,
I've been puzzled by how a random encounter could be scripted in games.

For example, say there's a secret travelling merchant that could be available at 12 locations.

My thinking at the moment is to use the random function to decide where the merchant would be on this day (beach), so if you don't choose to go to the beach, you won't see the merchant.

Another thought is: when the player goes to the park, a random function will decide whether the merchant will show (1/13 chance). If true, merchant will show up.

This thought came after playing FFIII, with the Legendary Smith.
I'm curious as to how these event logics are usually designed, please help?
Many thanks in advance

[kitsalai]

Both methods you mentioned will work fine. I believe most random encounters in modern games use psuedorandom generators as to make the player feel the sense of "randomness". You don't want to random hit a 10% chance two times in a row or never hit a 10% after 100 tries after all. For our purposes, renpy's random or python's random is suffice. http://www.renpy.org/doc/html/other.html#renpy-random

As to whether when you want to generate that random location is up to you. Note that if you random the location of the merchant before the player clicks the location, the player can save the game immediately beforehand and try up to 12 times to get it right. If you choose to generate the random encounter after the player clicks, it will make it more difficult for the player to find the merchant by saving/loading.

The design is up to you, but in my opinion I prefer the player to feel at ease and would select the merchant beforehand.

[Onishion]

Yeah, it might be nice to just schedule the merchant and let players learn the patter themselves. I tend to prefer rare but potentially predictable system to one that is truly random.

[trooper6]

Yeah, it might be nice to just schedule the merchant and let players learn the patter themselves. I tend to prefer rare but potentially predictable system to one that is truly random.

I also tend to prefer the "realistic" way...which is to give the merchant a schedule.

[Onishion]

Btw, is there some kind of "on rollback" trigger? If so, a fun little troll, without making rollback impossible, might be to make it so that the location is random, so in theory they could keep rolling back and retrying until the hit it right, but have a trigger so that if they do rollback at that time, it blocks the merchant out until the next "turn," whenever that is, so that even if they did get the right RNG roll for him to appear, he just wouldn't. It shouldn't cause any damage that they wouldn't already have if they were playing it fair.

[xela]

I think renpy.random "remembers" it's choices when rolling back. They would have to save/reload to get a new result. Otherwise, you can always lock the seed to use a separate function to make sure that even loading doesn't put your merchant in the new location. We discussed something like this in the cookbook long time ago.

[wjannsz]

ah... I was thinking inside a tiny box. I didn't think about the good old save/load method at all, even though I did that all the time when I played games :p. not being able to S/L does take out a lot of the fun.

If the player saves right before the clicking the location and then the merchant-random event runs, it would be easier for player to S/L, while possibly loses the point of me making merchant appearances random. I'll have to bear in mind the effect of the rollback function as well. (too many rollbacks will unlock achievements sounds like fun.)
from my past usage of renpy.random.choice, I believe that the choice will be the same when rolling back and forth.

Thanks for all your opinions and input above, I think from what you guys have suggested, I'll be going for scripted randomness. That is, patterns that are discoverable to players that have followed the stories/hidden hints, while to a new player it would be completely random.

Mmmm......i'll go get my thinking cap!

[morg]

there's one way to do that listed in the ren'py cookbook which i think you'll find very useful:
http://www.renpy.org/wiki/renpy/doc/coo ... han_others
i also have my own way i made up quickly..

Code: Select all

label start:
    $ visited_beach = 0
    $ visited_waterfall = 0
    call screen imagemap #imagemap that has all the locations
label beach:
    $ visited_beach += 1
    if visited_beach <= 13:
        "hm.. i can't find him here.."
        jump start
    else:
        show merchant
        "there you are!"
        #continue the story...
        
label park:
    #it is impossible to find him in the park
    "he isn't here"
    jump start
    
label waterfall:
    $ visited_waterfall += 1
    if visited_waterfall <= 10: #the chance of finding him in the waterfall is higher
        "he ain't here."
        jump start
    else:
        show merchant
        "there u are"
        #etc
        

and if you want to make the places the merchant can be random you could use the generator

Code: Select all

    $ place = renpy.random.choice(["beach", "park", "waterfall"])

and then adding it like so:

Code: Select all

define m = Character("Merchant")
label start:
    $ place = renpy.random.choice(["beach", "park", "waterfall"])
    $ visited_beach = 0
    $ visited_waterfall = 0
    call screen imagemap #imagemap that has all the locations
label beach:
    if place == "beach":
        $ visited_beach += 1
        if visited_beach <= 13:
            "hm.. i can't find him here.."
            jump start
        else:
            show merchant
           "there you are!"
           #continue the story...
    else:
        "he isn't here"
        jump start
label park:
    if place == "park":
        $ visited_park += 1
        if visited_park <= 13:
            "not here"
            jump start
        else:
            show merchant
            m "i see you've found me"
            "yeah. finally"
            #continue story or jump to label
    else:
        "he isn't here"
        jump start
    
label waterfall:
    if place == "waterfall":
        $ visited_waterfall += 1
        if visited_waterfall <= 10: #the chance of finding him in the waterfall is higher if the get it
            "he ain't here."
            jump start
        else:
            show merchant
            "there u are"
            #continue story or jump to the next event label
    else:
        "not here"
        jump start
    
        

ofcourse that's a ton of programming and may or may not suit you... and like what has been said the random generator can't be used how you want it because the result you get doesn't change until you restart, but it can be used to randomize events

[wjannsz]

hi morg,
thanks for directing me to that page and laying out a foundation for me.
i gave it a try and this is what i came up with.

Code: Select all

init python:
    class NonUniformRandom(object):
        def __init__(self, list_of_values_and_probabilities):
            """
            expects a list of [ (value, probability), (value, probability),...]
            """
            self.the_list = list_of_values_and_probabilities
            self.the_sum = sum([ v[1] for v in list_of_values_and_probabilities])

        def pick(self):
            """
            return a random value taking into account the probabilities
            """
            import random
            r = random.uniform(0, self.the_sum)
            s = 0.0
            for k, w in self.the_list:
                s += w
                if r < s: return k
            return k

define m = Character("Merchant")
label start:
    
    $choose = renpy.input("Where do you want to go today? beach, park or waterfall?")
    while choose != "beach" and choose != "park" and choose != "waterfall":
        "I'm sorry, [choose] is not available for visiting yet, please choose again."
        jump start
label places:
    $ locations = [('beach',10),('park',3),('waterfall',5)]
    $ place = NonUniformRandom(locations)
    if place.pick() == choose:
        "I see you've found me."
    else:
        "Nope, not here."
        jump start

i think this might do what i want. i put the generator after the click, and tested. the result will still change after rollback