port improvements to autobrake_test too, excluding the weird calc_targets thing

autobrake_test.p8

@@ -81,9 +81,10 @@ function _draw()
  print("dx: ".. the_ship.dx, 20, 86, 7)
  meter(80, 86, 128, 90, the_ship.dx/the_ship.maxspd/2)
  print("x: "..the_ship.x, 24, 92, 7)
+ print("bx: "..gbx, 20, 98, 7)
 
- print("xmin:"..tostr(constraints.xmin), 12, 102, 7)
- print("xmax:"..tostr(constraints.xmax), 12, 108, 7)
+ print("xmin:"..tostr(constraints.xmin), 12, 108, 7)
+ print("xmax:"..tostr(constraints.xmax), 12, 114, 7)
 end
 
 function meter(x0, y0, x1, y1, frac)
@@ -127,26 +128,24 @@ function ship:draw()
   spr(1,self.x,self.y)
  end
 
- if (self.dx == 0) return
+ --if (self.dx == 0) return
  local bd, f = brake_dist(self.dx, self.thrust + self.drag)
- local bdx = self.x+bd-2
- spr(3, bdx,self.y-2)
- print(tostr(f), bdx, self.y - 8, 14)
+ gbx = self.x+bd
+ spr(3, gbx-2,self.y-2)
+ print(tostr(f), gbx-2, self.y - 8, 14)
 end
 
 function calc_velocity(v0, t, vmax, drag)
- local v1 = v0 + t
- local sg = sgn(v1)
- v1 -= sg*drag
- if (sgn(v1) != sg) return 0
- if (abs(v1) > vmax) return sg*vmax
- return v1
+ v0 = mid(v0 + t, vmax, -vmax)
+ return v0 - mid(drag, -drag, v0)
 end
 
 function ship:update()
  local t = btn(0) and -1 or btn(1) and 1 or 0
  t *= self.thrust
  t = constraints:constrain(self, t)
+ -- t = constraints:constrain(self, t)
+ -- t = constraints:constrain(self, t)
  local s = calc_velocity(self.dx, t, self.maxspd, self.drag)
 
  self.x += s
@@ -165,10 +164,31 @@ constraints = {
 
 function constraints:constrain(s, want)
  self.color=10
+ if (not self.xmin) return want
 
- local v1 = calc_velocity(s.dx, want, s.maxspd, s.drag)
- local bd, bf = brake_dist(v1, s.thrust + s.drag)
-
+ -- bmx: brake max
+ local v1, bmx = calc_velocity(s.dx, want, s.maxspd, s.drag), s.thrust + s.drag
+ local bd, bf = brake_dist(v1, bmx)
+ local bx, txm = s.x + bd + v1, self.xmax
+ if bx < self.xmin then
+  -- predicted brake point left
+  -- of xmin; apply max reverse
+  -- thrust, treat xmin as our
+  -- max target, and handle
+  -- overbraking by coalescing
+  -- with past +xmax case
+  self.color = 9
+  want = s.thrust
+  txm = self.xmin
+  v1 = calc_velocity(s.dx, want, s.maxspd, s.drag)
+  bd, bf = brake_dist(v1, bmx)
+  bx  = bd + s.x + v1
+ end
+ if (bx <= txm) return want
+ self.color = 8
+ local overage = bx - txm
+ want -= overage/max(bf,1)
+ if (want < -s.thrust) want = -s.thrust
  return want
 end
 

vacuum_gambit.p8

@@ -420,6 +420,13 @@ ship_m = {
  
  xmomentum = 0,
  ymomentum = 0,
+
+ -- xmin, xmax, ymin, ymax:
+ --   movement constraints
+ --   enforced by `constrain`.
+ xmin = 0, xmax = 104,
+ -- ymin, ymax default to nil
+ --   pship needs more constraint 
 }
 mknew(ship_m)
 
@@ -428,31 +435,60 @@ function ship_m:die()
  if (self.hp <= 0) boom(self.x+self.size*4, self.y+self.size*4,12*self.size, self.boss)
 end
 
+function ship_m:calc_velocity(v0, t)
+ v0 = mid(v0 + t, self.maxspd, -self.maxspd)
+ return v0 - mid(self.drag, -self.drag, v0)
+end
+
+function ship_m:brake_dist(v0)
+ local brake_max = self.thrust + self.drag
+ local tri_frames = abs(v0\brake_max)
+ local chunks = tri_frames * (tri_frames - 1) >> 1
+ local chunk_zone = chunks * brake_max
+ local overage = abs(v0) - tri_frames * brake_max
+ return (chunk_zone + overage * (tri_frames + 1)) * sgn(v0), (overage > 0) and tri_frames + 1 or tri_frames
+end
+
+function ship_m:constrain(p, dp, pmin, pmax, want)
+ if (not pmin) return want
+ local v1, bd, bf, bp
+ function calc_targets()
+  -- velocity after move
+  v1 = self:calc_velocity(dp, want)
+  -- brake distance and frames
+  bd, bf = self:brake_dist(v1)
+  -- brake point
+  bp = p + bd + v1
+ end
+ calc_targets()
+ if bp < pmin then
+  -- undershoot. max thrust,
+  -- then treat as overshoot
+  -- targeting minimum bound
+  want, pmax = self.thrust, pmin
+  calc_targets()
+ end
+ if (bp <= pmax) return want
+ -- spread overshoot across frames
+ want -= (bp - pmax)/max(bf,1)
+ return max(want, -self.thrust)
+end
+
 function ship_m:move()
  self:refresh_shield()
  self.power = min(self.max_power, self.power + self.generator)
  local dx, dy, shoot_spec, shoot_main = self:act()
+ dx = self:constrain(self.x, self.xmomentum, self.xmin, self.xmax, dx)
+ dy = self:constrain(self.y, self.ymomentum, self.ymin, self.ymax, dy)
  if (shoot_main) self:maybe_shoot(self.main_gun)
  if (shoot_spec) self:maybe_shoot(self.special_gun)
  if (dx ~= 0 or dy ~= 0) spark(self.sparks, self.x + 4*self.size, self.y + 4*self.size, dx*2.5, dy*2.5, self.sparkodds)
- self.xmomentum += dx
- self.ymomentum += dy
- self.xmomentum = mid(-self.maxspd, self.maxspd, self.xmomentum)
- self.ymomentum = mid(-self.maxspd, self.maxspd, self.ymomentum)
- 
+ self.xmomentum = self:calc_velocity(self.xmomentum, dx)
+ self.ymomentum = self:calc_velocity(self.ymomentum, dy)
+
  self.x += self.xmomentum
  self.y += self.ymomentum
  
- if self == primary_ship then
-  self.x = mid(0, 112 - 8 * self.size, self.x)
-  self.y = mid(0, 128 - 8 * self.size, self.y)
- end
- 
- --friction
- local d = self.drag
- self.xmomentum -= mid(d, -d, self.xmomentum)
- self.ymomentum -= mid(d, -d, self.ymomentum)
- 
  -- "scrolling" behavior
  if self.slip then
   self.y += scrollrate
@@ -850,6 +886,7 @@ player = ship_m.new{
  ymomentum = 0,
  maxspd = 2.5, -- momentum cap
  thrust = 0.25, -- momentum added from button
+ ymin = 0, ymax = 120, -- stay on screen
  drag = 0.125, -- momentum lost per frame
  slip = false, -- does not slide down screen
  act = function(self)  -- fetch buttons