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Mapping entity orientation to direction

Posted: Sun Aug 01, 2021 1:27 pm
by Deadlock989
Re: https://lua-api.factorio.com/latest/Lua ... rientation

I have long suspected that for entities with arbitrary animation directions (vehicles, turrets, radar) there is not a linear relationship between the RealOrientation of the entity and the animation frame. I have struggled for a long, long time with projectile/beam origin offsets for turrets and finally resorted to rendering and testing like this:

orientations2.jpg
orientations2.jpg (188.61 KiB) Viewed 603 times

This helped a lot but for scripted effects it still wasn't quite right. It seemed as though the animation frame used was sometimes off.

So I tested it. This is a 64-direction vehicle with a test sprite sheet. The large number here is the animation frame number, the smaller rendered text below is the fraction value that the entity's orientation was set to:

orientations.jpg
orientations.jpg (328.02 KiB) Viewed 603 times

Notice the repetitions and missing numbers. If the relationship was linear then for each frame number N, the number below should be (N-1)/64. But it clearly isn't. You can see this in effect for yourself if you build a custom radar (radars are a weird entity with an orientation that advances per tick instead of being an actual animation) and watch it turning - it clearly speeds up and slows down as it approaches the vertical and horizontal directions.

So what is the formula in the source code for mapping orientation to direction?

Re: Small documentation improvement requests

Posted: Sun Aug 01, 2021 2:45 pm
by Klonan
Deadlock989 wrote:
Sun Aug 01, 2021 1:27 pm
So what is the formula in the source code for mapping orientation to direction?
There is some info here:
viewtopic.php?f=23&t=30074

Re: Small documentation improvement requests

Posted: Sun Aug 01, 2021 3:59 pm
by Deadlock989
Klonan wrote:
Sun Aug 01, 2021 2:45 pm
Deadlock989 wrote:
Sun Aug 01, 2021 1:27 pm
So what is the formula in the source code for mapping orientation to direction?
There is some info here:
viewtopic.php?f=23&t=30074
Thanks. From that I found a way of converting turret orientation to the frame number ("direction"), it's probably a stupid/horrible way of doing it but it works:

Code: Select all

local function reverse_projected_orientation(turn)
	turn = turn + 0.25
	local x = math.sin(turn * math.pi * 2)
	local y = -math.cos(turn * math.pi * 2)
	y = y * math.cos(math.pi / 4)
	return (math.atan2(x, -y) / (math.pi * 2)) - 0.25
end

local function orientation_to_direction(orientation,directions)
	return math.floor((reverse_projected_orientation(orientation)*directions)+0.5) % directions
end
orientations3.jpg
orientations3.jpg (39.05 KiB) Viewed 570 times