port ship constraints logic

This commit is contained in:
Kistaro Windrider 2024-08-16 19:20:30 -07:00
parent d33d7ad6d1
commit 9dc36a95ee
Signed by: kistaro
SSH Key Fingerprint: SHA256:TBE2ynfmJqsAf0CP6gsflA0q5X5wD5fVKWPsZ7eVUg8

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@ -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 +435,59 @@ 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
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)/(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