Floodlights
When turned on, a floodlight projects a beam of light at full
brightness until it hits an opaque block or reaches a maximum range.
The default range is 64 blocks, although this can be increased up to a
limit of 255 by changing the maxFloodlightRange configuration setting.
Light from a floodlight has the same properties as torchlight, so it
will prevent mob spawning, promote plant growth, and so on. It is not
sunlight, however, so it will not ignite skeletons or power solar
panels.
Most floodlights require a redstone signal to turn them on. Some types also have an internal switch.
Orientation
Starting with version 1.7, floodlights can face in any direction. When
placing a floodlight, the business end will point away from the face of
the block that you click on, so you may need to place a temporary block
to get it facing the right way.
Floodlight Types
This is the simplest to use as it needs
no power source, but it is the most expensive to make and requires
materials from the Nether.
Runs on acetylene gas. Cheap to make, but must be supplied with fuel.
Available when IndustrialCraft 2 is
installed. Slightly more expensive than the carbide floodlight, but
offers the convenience of electric power.
Limitations
Floodlights work by placing a line of invisible light-producing blocks
along the beam path. Putting a transparent block, such as glass,
directly in the path of the beam will prevent a light block from being
placed there, and so the light intensity will be slightly reduced in
the vicinity. However, this effect should not be noticeable unless you
place a lot of transparent blocks in a row. Also note that if you fill
the entire beam path (from the floodlight to the next opaque block)
with transparent blocks, the floodlight will not produce any light at
all.
In some situations, placing or removing blocks in a beam path may
result in the beam not being updated properly. In most cases, you
should be able to fix this by turning the floodlight off and on again.
If that doesn't work, or if stray light blocks remain after removing a
floodlight, you may need to force an update by temporarily placing a
block next to the affected area.
The light blocks are designed to be as unobtrusive as possible, and
will mostly behave the same way as air, but there is a possibility that
they might interfere with the operation of other mods. There is one
known issue in vanilla Minecraft: a large oak tree that grows near a
floodlight will be left with a hole where the beam passes through.
Other tree types are unaffected.
Turning a floodlight on or off causes a large number of lighting
updates. As of version 1.11.2, floodlights have "slow" turn-on and
turn-off characteristics, limiting the number of lighting updates that
can occur per tick, so this should not normally be a problem. However,
toggling a large number of floodlights simultaneously in a large open
areas could cause momentary lag.