Fix collision resolution at low fps

1 files changed, 39 insertions, 35 deletions

diff --git a/src/phys.lua b/src/phys.lua
index e55f5c7..9adb915 100644
--- a/src/phys.lua
+++ b/src/phys.lua
@@ -104,36 +104,32 @@ function phys.Box:get_rect()
       self.height
 end
 
-function box_in_tilemap(map, box)
+local function get_tilemap_collision_rect(map, box)
   local x, y, width, height = box:get_rect()
 
   if has_tile(map, to_tile_coords(x, y)) then
-    return true
+    return true, get_tile_rect(x, y)
   end
   if has_tile(map, to_tile_coords(x + width, y)) then
-    return true
+    return true, get_tile_rect(x + width, y)
   end
   if has_tile(map, to_tile_coords(x, y + height)) then
-    return true
+    return true, get_tile_rect(x, y + height)
   end
   if has_tile(map, to_tile_coords(x + width, y + height)) then
-    return true
+    return true, get_tile_rect(x + width, y + height)
   end
 
   local extra_x = math.floor(width / (TILESIZE - 1))
   local step = width / (extra_x + 1)
 
   for i = 1, extra_x do
-    if has_tile(
-      map, to_tile_coords(x + step * i, y))
-    then
-      return true
+    if has_tile(map, to_tile_coords(x + step * i, y)) then
+      return true, get_tile_rect(x + step * i, y)
     end
 
-    if has_tile(
-      map, to_tile_coords(x + step * i, y + height))
-    then
-      return true
+    if has_tile(map, to_tile_coords(x + step * i, y + height)) then
+      return true, get_tile_rect(x + step * i, y + height)
     end
   end
 
@@ -141,29 +137,29 @@ function box_in_tilemap(map, box)
   step = height / (extra_y + 1)
 
   for i = 1, extra_y do
-    if has_tile(
-      map, to_tile_coords(x, y + step * i))
-    then
-      return true
+    if has_tile(map, to_tile_coords(x, y + step * i)) then
+      return true, get_tile_rect(x, y + step * i)
     end
 
-    if has_tile(
-      map, to_tile_coords(x + width, y + step * i))
-    then
-      return true
+    if has_tile(map, to_tile_coords(x + width, y + step * i)) then
+      return true, get_tile_rect(x + width, y * step * i)
     end
   end
 
-  return value
+  return false
 end
 
-function collision_check(box)
+local function get_collision_rect(box)
   local box_x, box_y, box_width, box_height = box:get_rect()
   local other_x, other_y, other_width, other_height
 
   for _, tilemap in ipairs(box.tilemap_mask) do
-    if box_in_tilemap(tilemap, box) then
-      return true
+    local ok, tx, ty, t_width, t_height = get_tilemap_collision_rect(
+      tilemap,
+      box
+    )
+    if ok then
+      return true, tx, ty, t_width, t_height
     end
   end
 
@@ -178,7 +174,7 @@ function collision_check(box)
             box_x, box_y, box_width, box_height,
             other_x, other_y, other_width, other_height
           ) then
-        return true
+        return true, other_x, other_y, other_width, other_height
       end
       ::collision_check_continue::
     end
@@ -199,22 +195,30 @@ function phys.Box:update(velx, vely, dt)
   -- welc
   for i = 1, steps do
     local p = i / steps
-    local before
 
-    before = self.x
     self.x = self.x + velx * dt * p
-    if collision_check(self) then
-      self.touchx = velx > 0 and 1 or -1
+    local ok, otherx, othery, other_width, other_height = get_collision_rect(self)
+    if ok then
+      self.touchx = sign(velx)
       velx = 0
-      self.x = before
+      if self.touchx > 0 then
+        -- this - 0.001 is a hack to prevent some silly bug I can't figure out
+        self.x = otherx - self.width - self.offsetx - 0.001
+      elseif self.touchx < 0 then
+        self.x = otherx + other_width - self.offsetx
+      end
     end
 
-    before = self.y
     self.y = self.y + vely * dt * p
-    if collision_check(self) then
-      self.touchy = vely > 0 and 1 or -1
+    ok, otherx, othery, other_width, other_height = get_collision_rect(self)
+    if ok then
+      self.touchy = sign(vely)
       vely = 0
-      self.y = before
+      if self.touchy > 0 then
+        self.y = othery - self.height - self.offsety - 0.001
+      elseif self.touchy < 0 then
+        self.y = othery + other_height - self.offsety
+      end
     end
 
     if self:touching() then