test player-relative paths

segment/path update logic was somewhat backwards.

the result is definitely good enough for the kind of movements I want!

vacuum_gambit.p8

@@ -194,7 +194,9 @@ function updategame()
   interlude -= 1
  else
   current_wave = flotilla.new()
-  current_wave:load(rnd() > 0.5 and 7 or 0, 0, min(ones(waves_complete)\2, 4))
+  --current_wave:load(rnd() > 0.5 and 7 or 0, 0, min(ones(waves_complete)\2, 4))
+  current_wave:load(0, 0, min(ones(waves_complete)\2, 4))
+  current_wave:update()
  end
  events = filtermoved(events)
  appendmove(events, new_events)
@@ -466,9 +468,7 @@ ship_m = mknew{
  -- xmin, xmax, ymin, ymax:
  --   movement constraints
  --   enforced by `constrain`.
- xmin = 0, xmax = 104,
- -- ymin, ymax default to nil
- --   pship needs more constraint 
+ xmin = 0, xmax = 104, ymin = 0, ymax = 120
 }
 
 function ship_m:die()
@@ -510,6 +510,10 @@ function ship_m:brake_dist(v0)
  return (chunk_zone + overage * (tri_frames + 1)) * sgn(v0), (overage > 0) and tri_frames + 1 or tri_frames
 end
 
+function ship_m:reset_bounds()
+ self.xmin, self.xmax, self.ymin, self.ymax = 0, 104, 0, 120
+end
+
 function ship_m:constrain(p, dp, pmin, pmax, want)
  if (not pmin) return want
  local v1, bd, bf, bp
@@ -615,6 +619,190 @@ function ship_m:refresh_shield()
  self.shield_refresh_ready = gframe + self.shieldcooldown
 end
 
+-->8
+-- paths
+
+-- destination: a point the
+-- center of a ship approaches
+destination = mknew{
+ -- 0..1: a point on a line
+ -- segment from the ship's
+ -- flotilla spot to the player;
+ -- -1 means center of play area
+ anchor_frac=0,
+
+ -- (0, 1]: relative to max
+ -- acceleration, how quickly
+ -- should the ship accelerate
+ -- to its destination?
+ -- 0: park here instead, using
+ -- constraint following
+ accel_frac=1,
+
+ -- how far to lerp between the
+ -- anchor and the screen bounds.
+ -- this is the "destination"-y
+ -- part of a destination.
+ x_off_frac = 0,
+ y_off_frac = 0
+}
+
+function lerp(a, b, f)
+ return (1-f)*a+b*f
+end
+
+function destination:anchor(fx, fy)
+ local af = self.anchor_frac
+ if (af == -1) return 51,59
+ return lerp(fx, primary_ship.x, af), lerp(fy, primary_ship.y, af)
+end
+
+function destination:target_from(fx, fy)
+ local rx, ry = self:anchor(fx, fy)
+ local xf, yf = self.x_off_frac, self.y_off_frac
+ if (xf < 0) rx = lerp(rx, 0, -xf)
+ if (xf > 0) rx = lerp(rx, 104, xf)
+ if (yf < 0) ry = lerp(ry, 0, -yf)
+ if (yf > 0) ry = lerp(ry, 120, yf)
+ return rx, ry, self.accel_frac
+end
+
+segment = mknew{
+ -- On loop, where to set index?
+ loop_idx = 1,
+ -- current index
+ current_idx = 1,
+ -- how long does this segment
+ -- last? 0 is erroneous,
+ -- positive values are a frame
+ -- count, negative values are
+ -- a number of loops.
+ limit = -1,
+
+ -- remain: remaining steps until end
+ -- prev_x, prev_y: stored previous
+ --  location to figure out
+ --  approach/depart
+ -- dest_x, dest_y: stored
+ --  current destination to
+ --  figure out approach/depart
+ -- dests[1..n]: destinations
+ init = function(x)
+  x.init = segment.reset
+  mknew(x)
+  if not x.mirror then
+   local mdests = {}
+   for i, v in ipairs(x.dests) do
+    mdests[i] = destination.new{
+     anchor_frac=v.anchor_frac,
+     accel_frac=v.accel_frac,
+     x_off_frac=-v.x_off_frac,
+     y_off_frac=v.y_off_frac,
+    }
+   end
+   x.mirror = mknew(x.new{mirror=x, init=segment.reset, dests=mdests})
+  end
+ end
+}
+
+function segment:reset()
+ self.current_idx = 1
+ self.remain = self.limit
+ self.prev_x = false
+ self.prev_y = false
+ self.was_approaching = false
+end
+
+function segment:target_from(fx, fy)
+ local rx, ry, af = self.dests[self.current_idx]:target_from(fx, fy)
+ self.dest_x, self.dest_y = rx, ry
+ return rx, ry, af
+end
+
+function segment:update(x, y)
+ local rem = self.remain
+ -- frame check
+ if (rem > 0) rem -= 1
+
+ if self:should_step(x, y) then
+  self.prev_x, self.prev_y, self.was_approaching = false, false, false
+  if self.current_idx == #self.dests then
+   self.current_idx = self.loop_idx
+   if (rem < 0) rem += 1
+  else
+   self.current_idx += 1
+  end
+ end
+ self.remain = rem
+ return rem != 0
+end
+
+function segment:should_step(x, y)
+ local dest_x, dest_y = self.dest_x, self.dest_y
+ local dx1, dy1 = x - dest_x, y-dest_y
+ if (abs(dx1) <= 1.5 and abs(dy1) <= 1.5) return true
+ if self.prev_x then
+  local dx0, dy0 = self.prev_x - dest_x, self.prev_y - dest_y
+  local d12, d02 = dx1 * dx1 + dy1 * dy1, dx0 * dx0 + dy0 * dy0
+  if d12 > d02 then
+   if (self.was_approaching) return true
+  else
+   if (d12 == d02 and self.was_approaching) return true
+   self.was_approaching = true
+  end
+ end
+ self.prev_x, self.prev_y = x, y
+ return false
+end
+
+path = mknew {
+ loop_idx = 1,
+ -- segs[1..n]: segments or subpaths
+ init=function(x)
+  if not x.mirror then
+   local msegs = {}
+   for i, v in ipairs(x.segs) do
+    msegs[i]=v.mirror
+   end
+   x.mirror = path.new{mirror=x, loop_idx=x.loop_idx, segs=msegs}
+  end
+  x.init = function(y)
+   local ysegs = {}
+   for i, v in ipairs(x.segs) do
+    ysegs[i]=v.new{}
+   end
+   y.segs = ysegs
+   y:reset()
+  end
+  mknew(x)
+ end,
+}
+
+function path:reset()
+ self.current_idx = 1
+ for s in all(self.segs) do
+  s:reset()
+ end
+end
+
+function path:target_from(fx, fy)
+ return self.segs[self.current_idx]:target_from(fx, fy)
+end
+
+function path:update(x, y)
+ local idx, segs = self.current_idx, self.segs
+ if not segs[idx]:update(x, y) then
+  segs[idx]:reset()
+  if idx == #segs then
+   self.current_idx = self.loop_idx
+   return
+  else
+   self.current_idx = idx+1
+  end
+ end
+ return true
+end
+
 -->8
 -- bullet and gun behaviors
 
@@ -1089,7 +1277,6 @@ player = mknew(ship_m.new{
  ymomentum = 0,
  maxspd = 1.5, -- momentum cap
  thrust = 0.1875, -- momentum added from button
- ymin = 0, ymax = 120, -- stay on screen
  drag = 0.0625, -- momentum lost per frame
  act = function(self)  -- fetch buttons
   local b,th = btn(),self.thrust
@@ -1303,13 +1490,76 @@ ship_f = mknew(ship_m.new{
  act = function(self)
   local wx,wy=self.want_x,self.want_y
   self.xmin,self.xmax,self.ymin,self.ymax = wx,wx,wy,wy
-  return 0,0,false,false
+  return 0,0
  end,
  init = function(self)
   if (self.gun_proto) self.main_gun = self.gun_proto.new()
+  if (self.path) self.path = self.path.new()
  end
 })
 
+diamond_loop = segment.new{
+ dests = {
+  destination.new{
+   x_off_frac=0.125
+  }, destination.new{
+   y_off_frac=0.125
+  }, destination.new {
+   x_off_frac = -0.125
+  }, destination.new {
+   y_off_frac = -0.125
+  },
+ },
+}
+
+park = segment.new{
+ dests = {
+  destination.new{
+   accel_frac = 0
+  }
+ }
+}
+
+diamond_bounce = path.new{
+ segs = {
+  park,
+  diamond_loop,
+  park,
+  diamond_loop.mirror,
+ },
+}
+
+swoop = segment.new {
+ dests = {
+  destination.new{
+   accel_frac = 0
+  }, destination.new{
+   x_off_frac = -0.75,
+   anchor_frac = 0.25,
+  }, destination.new {
+   x_off_frac = -0.375,
+   anchor_frac = 0.625,
+  }, destination.new {
+   y_off_frac = -0.125,
+   anchor_frac = 1,
+  }, destination.new {
+   x_off_frac = 0.375,
+   anchor_frac = 0.625,
+  },
+ },
+}
+
+swoop_loop = path.new {
+ segs = {
+  diamond_loop,
+  swoop,
+  park,
+  diamond_loop.mirror,
+  swoop.mirror,
+  park,
+ }
+}
+
 ship_mook = mknew(ship_f.new{
  sprite=103
 })
@@ -1326,11 +1576,37 @@ ship_turret = mknew(ship_f.new{
 ship_skirmisher = mknew(ship_f.new{
  sprite=107,
  xp = 0x0.0004,
+ hp = 1.5,
  sparks = smokespark,
  sparkodds = 3,
  fire_off_y = 7,
+ xmin = -8,
+ xmax = 112,
+ path = swoop_loop,
 })
 
+function ship_skirmisher:reset_bounds()
+ self.xmin, self.xmax, self.ymin, self.ymax = -8, 112, 0, 128
+end
+
+function ship_skirmisher:act()
+ local tx, ty, af = self.path:target_from(self.want_x, self.want_y)
+ if af <= 0 then
+  self.xmin, self.xmax, self.ymin, self.ymax = tx,tx,ty,ty
+  return 0,0
+ end
+ self:reset_bounds()
+ local ax, ay, th = tx - self.x, ty - self.y, self.thrust*af
+ local ma = max(abs(ax), abs(ay))
+ return ax*th/ma, ay*th/ma
+end
+
+function ship_skirmisher:move()
+ if (not ship_f.move(self)) return
+ if (not self.path:update(self.x, self.y)) self.path:reset()
+ return true
+end
+
 function rnd_spawn_loc()
  local x,y = flr(rnd(304)), flr(rnd(32))
  if (x<184) return x-40,-y-8
@@ -1431,7 +1707,7 @@ flotilla = mknew{
    [8]=mknew(ship_turret.new{ship_t=8}),
    [9]=mknew(ship_turret.new{ship_t=9, sprite=4}),
    [12]=mknew(ship_skirmisher.new{ship_t=12}),
-   [13]=mknew(ship_skirmisher.new{ship_t=13, sprite=26}),
+   [13]=mknew(ship_skirmisher.new{ship_t=13, sprite=26, path=diamond_bounce}),
   }
  end,
 }
@@ -1447,6 +1723,7 @@ function flotilla:load(ulc_cx, ulc_cy, lvl)
   [12]=0,
   [13]=0,
  }
+ local maxcol = 0
  repeat
   local row,cx,opt,f,mode = {},ulc_cx,{},0,0
   for i,v in ipairs(self.opt_odds) do
@@ -1458,7 +1735,7 @@ function flotilla:load(ulc_cx, ulc_cy, lvl)
    mode = f&0x03
    if mode==2 then
     -- bits 0x0c: ship class
-    local ship_t = f&0x0c
+    local ship_t, col = f&0x0c, cx-ulc_cx
     -- bit 0x20: optional?
     if f&0x20 == 0 or opt[ship_t] then
      -- bit 0x10: alternate ship?
@@ -1467,7 +1744,8 @@ function flotilla:load(ulc_cx, ulc_cy, lvl)
      -- and we allow alternates
      -- for this type of ship
      ship_t+=(uv>>ship_t&0x1)&((f&0x10)>>4)
-     add(row, self.ship_bases[ship_t].new{col=cx-ulc_cx})
+     add(row, self.ship_bases[ship_t].new{col=col})
+     if (col > maxcol) maxcol = col
     end
    end
    cx += 1
@@ -1487,6 +1765,13 @@ function flotilla:load(ulc_cx, ulc_cy, lvl)
   -- control mark bit 0x04: end of flotilla
  until f&0x04 > 0
  self.rows=rows
+ -- mirror right half paths; alternate center column if odd
+ local rh = maxcol>>1
+ for r, row in ipairs(rows) do
+  for s in all(row) do
+   if ((s.path) and (s.col > rh or (s.col == rh and r & 1 == 1))) s.path = s.path.mirror.new()
+  end
+ end
  self:statisfy(counts)
 end