The lightsaber scrolling effect is the gradual activation or deactivation of individual LEDs within a lightsaber lightsaber blade. The purpose of the scrolling effect is to mimic the extension and retraction effect of the lightsaber blade in the Star Wars films. A real life lightsaber, however, has a plastic blade attached to the hilt. The scrolling effect within the plastic blade imitates the extension and retraction of the energy blade within the Star Wars films.
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Not all lightsabers are capable of the scrolling effect. The lightsaber use a blade that contains a series or strip of LEDs. String blades and neopixel blades contain LEDs within the blade. Lightsabers that use in-hilt LEDs cannot accomplish the scrolling effect. In-hilt LEDs use one light source in the emitter area of the hilt so you can’t isolate when the light reaches certain segments of the blade. The blade is either illuminated or it’s dark–it’s on or it’s off.
Many Star Wars Force FX lightsabers, which are equipped with string blades, use the scrolling effect. Some lower-end lightsaber and lightsaber-like toys use the scrolling effect as well. For example, the Walmart Space Sword, which retails for under $5, uses the scrolling effect.
The lightsaber scrolling effect is cool visual effect intended to add some realism to the activation and deactivation of lightsaber. Only lightsabers that use LEDs within the lightsaber blade can accomplish the saber scrolling effect. In-hilt LEDs are incapable of the visual effect.