Event Jitter Fix / Display Rounding Error Fix

Discussion in 'RGSS3 Scripts (RMVX Ace)' started by Neon Black, Aug 27, 2013.

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  1. Neon Black

    Neon Black The Classy Prostitute Member

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    Scroll down to the red bolded text if you just want the fix.

    Recently it was brought to my attention that when scrolling the map with a lot of events on screen, the events would "jump" by a single pixel and would be improperly positioned.  I initially shrugged this off as lag, but when I saw the same effects on my absolutely awesome machine I wasn't quite sure what was up.  I decided I would look into it a little bit more.  When I tried to recreate it on my own by packing a screen full of events and then scrolling I was unable to reproduce the results.  It wasn't until I tested the issue with the demo in a related topic that I noticed the issue seemed to have to do with slow speed panning.

    Essentially what I discovered is that events and the tilemap were rounding extremely low values from "display_x" and "display_y" differently.  The tilemap always rounded up while characters/events always rounded down.  What do I mean by extremely low values?  Because of the formula used to calculate scroll distance (2 ** @scroll_speed / 256.0) the display points can end up being values such as 15.5 pixels.  As mentioned earlier, the tilemap would round this up to 16 while the events would round this down to 15.  This would cause events to display 1 pixel away from where they were supposed to.

    To fix the issue I modified two things to ensure that tilemaps and events would always get the same value.  First of all I added two methods to replace the normal reader methods for the displays.  In these I just multiplied by 32, used .floor to round down, switched it back to a floating point value, and divided it by 32.  This ensured that when received by anything that might use the display values, it was always rounded to the lowest values without any further need for coercing.  Secondly, I modified the two "adjust" methods used to determine the X and Y positions of events to reference the new reader methods rather than using the variable directly.

    Anyway, all that done, here's the snippet.  Be sure to place this under materials and above all additional custom scripts since this is meant to be a bugfix of the default scripts.

    Pastebin link: http://pastebin.com/XDd0tVWJ

    Full Script:

    Code:
    ##------## Display rounding error fix created by Neon Black.#### When certain slow display panning speeds are used, events will improperly## round floating values to determine their position on screen.  This causes## them to appear off from the tilemap by a single pixel.  Though minor this is## noticable.  This snippet fixes this behaviour.#### This snippet may be used in any project.##------ class Game_Map ## Rounds X and Y display values DOWN so the nearest 32 is found.  def display_x    (@display_x * 32).floor.to_f / 32  end    def display_y    (@display_y * 32).floor.to_f / 32  end    def adjust_x(x)    if loop_horizontal? && x < display_x - (width - screen_tile_x) / 2      x - display_x + @map.width    else      x - display_x    end  end    def adjust_y(y)    if loop_vertical? && y < display_y - (height - screen_tile_y) / 2      y - display_y + @map.height    else      y - display_y    end  endend
     
    Last edited by a moderator: Aug 27, 2013
    #1
    Sindaine, Fallun, Marsigne and 11 others like this.
  2. Galv

    Galv Veteran Veteran

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    Fantastic! I can't thank you enough for this. I couldn't work it out myself, very nice.
     
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  3. Kenen

    Kenen Veteran Veteran

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    Your eye for precision and quality is outstanding, Neon Black. Thank you for the fix!
     
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  4. Engr. Adiktuzmiko

    Engr. Adiktuzmiko Chemical Engineer, Game Developer, Using BlinkBoy' Veteran

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    wow, it's cool that you even noticed that 1 pixel deviation...
     
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  5. Megablackdragon31

    Megablackdragon31 Veteran Veteran

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    Long time no see,Neon Black.

    Thanks you very much for the fix,you are a life saver.
     
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  6. estriole

    estriole Veteran Veteran

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    omg! i think you really have photographic memory. not everyone can notice that 1 pixel difference :D . good job neon :D .
     
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  7. Zachy

    Zachy Veteran Veteran

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    This is exactly what I needed, thank you for the great fix.
     
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  8. Fallun

    Fallun Villager Member

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    Wow! awesome! <3 needed this fix!! 
     
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  9. TheWhiteRose000

    TheWhiteRose000 Veteran Veteran

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    This actually helped me a lot, as I got a lot of visual scripts running and its very taxing.

    Wish I could smooth it out more but, beggars can't be choosers.
     
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  10. StarWarrior00

    StarWarrior00 ~ King of Cuteness ~ Veteran

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    What are the terms of use for the script?
     
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