How do i make a thing flash in and out of existence? Like the Invis-orb in Zdoom.

[Ezxariarch]

When i DLed ZDoom i saw that the Partial incisability orb flashes in and out of existance by changing its tranparency. I wanted to know howto do that for a TC im working on. I also saw this done on Ghost-Busters Doom 2. They made the "Giga-meter" (chaingun replacement) do that. So...any one got any ideas??? ^_^

[SpinSpyder_KaK_]

Might try using an OPEN script to repeatedly increase and decrease the translucency of an object.