quick question about some entity code

[fessmK]

Hello all, long time no see.
I ran into an interesting problem while running an experimental entity.
error:

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2017-12-06 15:09:01: ACTION[Server]: singleplayer invokes /spawnentity, entityname="test:basic_mob"
2017-12-06 15:09:01: [Server]: 2
2017-12-06 15:09:01: ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: Runtime error from mod 'test' in callback luaentity_Step(): Invalid float vector dimension range 'x' (expected -2.14748e+006 < x < 2.14748e+006 got nan).
2017-12-06 15:09:01: ERROR[Main]: stack traceback:
2017-12-06 15:09:01: ERROR[Main]: 	[C]: in function 'setvelocity'
2017-12-06 15:09:01: ERROR[Main]: 	...test-0.4.16-win64\bin\..\games\temple\mods\test\init.lua:50: in function 'set_velocity'
2017-12-06 15:09:01: ERROR[Main]: 	...test-0.4.16-win64\bin\..\games\temple\mods\test\init.lua:126: in function 'func'
2017-12-06 15:09:01: ERROR[Main]: 	...0.4.16-win64\bin\..\builtin\profiler\instrumentation.lua:106: in function <...0.4.16-win64\bin\..\builtin\profiler\instrumentation.lua:100>

here is the function:

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set_velocity = function(self, v)
		
		local yaw = self.object:getyaw()
		if self.drawtype == "side" then
			yaw = yaw+(math.pi/2)
		end
		local x = math.sin(yaw) * -v
		local z = math.cos(yaw) * v
		self.object:setvelocity({x=x, y=self.object:getvelocity().y, z=z}) --sometimes crashes because a NaN is passed to x
	end,

and the parameters when called:(only called in on_step(dtime))

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minetest.debug(self.run_velocity) --reason for all those 2s
self.set_velocity(self, self.run_velocity)

--and

self.set_velocity(self, 0)

I tried checking to see if the variable x, and z, were numbers, but that always came back as true.


this experimental code was based on PlzAdam's Mobs mod

[Krock]

NaN is represented in the 64-bit IEEE floating point number, which Lua uses by default for numbers. So it reasonable that checking this against being the number type succeeds every time.

More interesting would be where "self.run_velocity" comes from, as "math.sin(0/0)" (passing NaN as function argument) returns NaN, which gets then passed to "self.object:setvelocity".

PS: "setvelocity" and "getyaw" (and similar) are deprecated. Use "set_velocity" and "get_yaw" instead.

[fessmK]

More interesting would be where "self.run_velocity" comes from

it is set to 2

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run_velocity = 2,

edit: it is probably worth mentioning that, after the initial spawn with /spawnentity and the resulting crash, it runs just fine. Also, using an item to spawn the entity does not result in a crash.