Blender Game Engine Overview | Page 4

object without sensors is automatically collapsed. Adding a sensor will automatically show the
object.

Common Sensor Options
All sensors have a set of buttons and fields and menu in common. They are organized in the two rows:
the sensor header and the sensor pulses bar .
Sensor Header

Sensor header

Triangle button
Collapses the sensor.
Sensor type menu
See sensor types.
Sensor name
The name of the sensor. It is used to access sensors with python; it needs to be unique among the
selected objects.
X Button
Deletes the sensor.


Sensor Pulses Bar
Sensors fire pulses to controllers. The pulses can be TRU E or FALSE. Different parameters on the
sensor's logic block control when a sensor fires what pulse. This is extremly important as it has direct

influence on the game logic and the performance. It is up to the controllers how to react on TRUE and
FALSE pulses.


Sensor pulses bar
True level triggering
If this is set, the controllers receive TRUE pulses as long as the sens or's state is positive. The
sensor will fire TRUE pulses with the frequency of the sensor.
False level triggering
If this is set, the controllers receive FALSE pulses as long as the sensor's state is negative. The
sensor will fire FALSE pulses with the frequency of the sensor.
Note about triggers
If you don't set any triggers, the sensor fires no pulse at all as long t he sensor's state does
not change. When the sensor changes it's state from negative to positive t he sensor fires
one TRUE pulse to the controllers. When sensor changes it's state from positive to
negative the sensor fires one FALSE pulse to the controllers.
In between the controllers might still request the sensor's state, but if the controller does
not get pulses (TRUE or FALSE) from any other sensor it will not be act ivated at all.
Frequency
Despite the name, "Frequency", the f parameter sets the delay between repeated pulses, measure d
in logic ticks. The default value is 0 and it means no delay.
Logic ticks have a frequency of 60 Hz (60 ticks per second). For example:
 setting f=1 means the sensor pulses once every 60th of a second. A setting of f = 1,
effectively means a 1 to 1 ratio between ticks, 1 tick = 1 pulse.
 setting f=30 means the sensor pulses once after 30 ticks have elapsed. Thi s means the
pulse is emitted every half a second because there are 60 ticks per second by default.
 setting f=60 means the sensor pulses every 60 ticks, which means one time per second
Raising the value of f is good for saving performance by not doing things more often than
necessary.

Level Button

Makes the sensor working over state changes. See this page for the state system.
Tap Button
Sends a positive pulse only once even if the sensor remains true. Only one of Tap or Level can be
activated.
When the Tap parameter is set the sensor will fire a FALSE pulse within t he next frame, even
when the sensor event is still present. When the sensor's event goes away no pulse will be fired.
If the TRUE level triggering is set, the TRUE/FALSE pulse pair will be repeated until the sensor's
event goes away.
The FALSE level triggering will be ignored when the Tap parameter is set.
Pulses will not be inverted when the Inv parameter is set. But the TRUE/FALSE pulse pair will
be send when the sensor's event is not present.
Invert Button
This inverts the sensor output.
If this is set, the sensor will send FALSE pulses when the sensor should se nd TRUE pulses and
TRUE pulses if the sensor should send FALSE pulses. If the Tap parameter is set, the sensor acts
different (refer to the previous section).
Note about Inv and triggers
Note that the toggle Inv inverts the level BEFORE the triggers, which means the triggers a ct on the signal coming out from Inv.
As a test, setup the logic bricks as below on an object of your choic e.



Start the game