Drawing a Line at runtime

ID:178876
 
Mar 23 2002, 9:49 pm
I'm looking for an way to draw lasers in my game. What I'd like to do to represent this is just have a line drawn from the source to the target if they are close enough.

Can anyone tell me the proc if there is one to do this?

LJR
Mar 23 2002, 10:22 pm
Mar 23 2002, 10:23 pm
In response to Sob
Thanks but no thanks ;)
I'm the like to know how its done coder of BYOND! :P

LJR
Mar 23 2002, 11:01 pm
In response to LordJR
LordJR wrote:
Thanks but no thanks ;)
I'm the like to know how its done coder of BYOND! :P

s_missile probably wouldn't suit your purposes there anyway, since it's designed for graphical missiles that fly to their targets. =P
Mar 23 2002, 11:02 pm
In response to Spuzzum
Spuzzum wrote:
LordJR wrote:
Thanks but no thanks ;)
I'm the like to know how its done coder of BYOND! :P

s_missile probably wouldn't suit your purposes there anyway, since it's designed for graphical missiles that fly to their targets. =P

Yeah I knew, I just didn't want to insult him :)

LJR
Mar 24 2002, 9:51 am
In response to LordJR
Well in case anyone missed this, I can't find anything where it talked about Drawing.. What kinda procs are theses?? Is this new stuff since the Book came out?

LJR
Mar 24 2002, 12:11 pm (Edited on Mar 24 2002, 12:23 pm)
In response to LordJR
I started working on the problem and this is what I have so far. It won't draw an entire line from the src to the target but it will create a laser pulse (one turf large) that is aligned with the target.
mob
  verb
    Shoot(var/mob/M as mob in oview(8))
      var/hypotenuse = sqrt((M.x - x)**2 + (M.y - y)**2)
      var/angle = round(arccos((M.x - x)/hypotenuse))
      var/icon/I = new('laser2.dmi')
      if(M.y > y)
        angle *= -1
      angle += 45
      I.Turn(angle)
      missile(I,src,M)


You need to draw the laser icon from the bottum left corner to the top right corner of the icon. It doesn't need to be continuous just with that orientation (meaning it could be several torpedoes instead of one continuous beam).

This will make use of the entire turf length of the turf. If you don't mind it partially filling the turf you can get rid of the angle += 45 line and make your icons from left center to right center (horizontally). It just depends on what you want.

Anyway, I might try to allow one continuous beam but I'll have to think about that because the shifts involved could be troublesome.
Mar 25 2002, 11:30 am
In response to LordJR
LordJR wrote:
Well in case anyone missed this, I can't find anything where it talked about Drawing.. What kinda procs are theses?? Is this new stuff since the Book came out?

There are no drawing procs (yet) in the /icon class, but icon.Blend() can be used to take special single-pixel icons and overlay them.
/*
    This requires pixel.dmi to be a white pixel at the lower left corner
    of an otherwise transparent pixmap.

    x,y coords are 0-based, not 1-based; no limit checking is done, so
    they should be 0-31.
 */

DrawPixel(icon/ic,x,y,color)
  var/icon/pixel=new /icon('pixel.dmi')
  pixel.Blend(color,ICON_MULTIPLY)
  pixel.Shift(EAST,x)
  pixel.Shift(NORTH,y)
  ic.Blend(pixel,ICON_OVERLAY)

Obviously that proc is massively inefficient; it's better to cache a colored pixel first.

Lummox JR
Mar 26 2002, 3:47 am
In response to English
Ok.. I've not had much exp. with this so I'm wondering if anyone can suggest some ways that I could do this syntax wise.

I've drawn 3 framed animated icons of my lasers when they fire, since there are no draw commands yet. So what I need to know now, is how to check 3 spaces in front of the mob, also how to define which side of the mob is the front. So when they fire, it shots out the lasers up to 3 spaces ahead, if any objs or mobs are encounted during this check it stops, and does a check to see if its a valid target, if so damage is done.

LJR

ps. I have heard some people recommend the missle() for this, but I'm worried about this considering there is no movement from source to target like a missle, but a instant 3 tile line and anything in the way gets hit.
Mar 26 2002, 5:14 am
In response to LordJR
LordJR wrote:
Ok.. I've not had much exp. with this so I'm wondering if anyone can suggest some ways that I could do this syntax wise.

I've drawn 3 framed animated icons of my lasers when they fire, since there are no draw commands yet. So what I need to know now, is how to check 3 spaces in front of the mob, also how to define which side of the mob is the front. So when they fire, it shots out the lasers up to 3 spaces ahead, if any objs or mobs are encounted during this check it stops, and does a check to see if its a valid target, if so damage is done.

missile() is clearly not what you want. I believe you want a simple straight line between two arbitrary tiles. Well, then you're going to want an algorithm to make the icons for you:
/*
    Draw a laser going dx tiles east, dy tiles north, centered
    in each tile. This proc returns an associative list that's
    meant to be cached for quick lookup. For convenience, keep
    dx>=0.

    'laser.dmi' should be a single icon, a white pixel at 16,16
    and all other pixels transparent.

    This laser is white. To color it in, I recommend using an associative
    list as a cache to store the colored icons. The laser is a single
    pixel line, but this code can be modified (not easily, mind you)
    to produce thicker lines.
 */

proc/CreateLaser(dx,dy)
  var/cachekey="[dx,dy]"
  var/list/L=list()
  var/icon/lasershifted=new /icon('laser.dmi')
  var/unitstomove=max(dx,dy)*32
  var/xinc1=0
  var/yinc1=0
  var/xinc2=0
  var/yinc2=0
  var/maindir=EAST
  var/sidedir=(dy>=0)?NORTH:SOUTH
  if(dx>dy)
    xinc1=1
    yinc2=(dy>=0)?1:-1
  else
    yinc1=(dy>=0)?1:-1
    xinc2=1
    maindir=sidedir
    sidedir=EAST
    var/swap=dx
    dx=dy
    dy=swap
  var/mainsub=(dx>=0)?16:15
  var/sidesub=(dy>=0)?16:15
  dx=abs(dx)
  dy=abs(dy)
  var/centerx=0   // coords of current tile
  var/centery=0
  var/aside=dx
  var/icon/current
  for(var/n=0,n<=unitstomove,++n)
    current=L["[centerx],[centery]"]
    if(!current)
      current=new /icon(lasershifted)
      L["[centerx],[centery]"]=current
    else
      current.Blend(lasershifted,ICON_OVERLAY)
    lasershifted.Shift(maindir,1,1)    // wrap
    aside+=dy
    mainsub=(mainsub+1)&31
    if(!mainsub)
      centerx+=xinc1
      centery+=yinc2
    if(aside>dx+dx)
      aside%=dx
      lasershifted.Shift(sidedir,1,1)  // wrap
      sidesub=(sidesub+1)&31
      if(!sidesub)
        centerx+=xinc2
        centery+=yinc2
  lasercache[cachekey]=L
  return L

I wrote that mostly as an exercise to see what I could come up with. Code to draw a thicker laser would be slightly harder because you'd need 1) to use ICON_ADD and icons with small circle and a black background, followed by a call to SwapColor() at the very end to replace black with the mask, and 2) to add to more than one icon at a time when the shifted circle covers more than one tile.

Lummox JR