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custom_physics.lua

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+local min = math.min
+local abs = math.abs
+
+function ap_airship.physics(self)
+    local friction = 0.996
+	local vel=self.object:get_velocity()
+		-- dumb friction
+	if self.isonground and not self.isinliquid then
+        --minetest.chat_send_all("with friction")
+		vel = {x=vel.x*friction,
+								y=vel.y,
+								z=vel.z*friction}
+        self.object:set_velocity(vel)
+	end
+	
+	-- bounciness
+	if self.springiness and self.springiness > 0 then
+		local vnew = vector.new(vel)
+		
+		if not self.collided then						-- ugly workaround for inconsistent collisions
+			for _,k in ipairs({'y','z','x'}) do
+				if vel[k]==0 and abs(self.lastvelocity[k])> 0.1 then
+					vnew[k]=-self.lastvelocity[k]*self.springiness
+				end
+			end
+		end
+		
+		if not vector.equals(vel,vnew) then
+			self.collided = true
+		else
+			if self.collided then
+				vnew = vector.new(self.lastvelocity)
+			end
+			self.collided = false
+		end
+		--minetest.chat_send_all("vnew")
+		self.object:set_velocity(vnew)
+    end
+    --[[else
+        self.object:set_pos(self.object:get_pos())
+        if not self.isonground then
+            --minetest.chat_send_all("test")
+            self.object:set_velocity(vel)
+        end
+	end]]--
+
+	--buoyancy
+	local surface = nil
+	local surfnodename = nil
+	local spos = airutils.get_stand_pos(self)
+	spos.y = spos.y+0.01
+	-- get surface height
+	local snodepos = airutils.get_node_pos(spos)
+	local surfnode = airutils.nodeatpos(spos)
+	while surfnode and (surfnode.drawtype == 'liquid' or surfnode.drawtype == 'flowingliquid') do
+		surfnodename = surfnode.name
+		surface = snodepos.y +0.5
+		if surface > spos.y+self.height then break end
+		snodepos.y = snodepos.y+1
+		surfnode = airutils.nodeatpos(snodepos)
+	end
+
+    local new_velocity = nil
+
+    local accell = {x=0, y=0, z=0}
+    self.water_drag = 0.1
+    self.object:move_to(self.object:get_pos())
+    local time_correction = (self.dtime/ap_airship.ideal_step)
+    local y_accel = self._baloon_buoyancy*time_correction
+    --minetest.chat_send_all(y_accel)
+    local max_y_acell = 0.3
+    if y_accel > max_y_acell then y_accel = max_y_acell end
+    if y_accel < (-1*max_y_acell) then y_accel = -1*max_y_acell end
+
+
+    self.isinliquid = false
+    if self._baloon_buoyancy == 0 then
+        local velocity = vector.new(vel)
+        velocity.y = velocity.y - (velocity.y/100)
+        self.object:set_velocity(velocity)
+    end
+    --minetest.chat_send_all("_baloon_buoyancy: "..self._baloon_buoyancy.." - dtime: "..self.dtime.." - ideal: "..ap_airship.ideal_step)
+    airutils.set_acceleration(self.object,{x=0,y=y_accel,z=0})
+
+    
+end