Looks like a missing dependency. See what else the Instant Massive Structures Mod needs you to have set up beforehand.
Also in the 1.8 snapshots there's a spectate mode (gamemode 3) that renders you invisible and such, and also able to hop into the bodies of other players and mobs to watch from their PoV. And when spectating inside some mobs, shaders are used for various visual effects.
Spider...
Creeper...
Also in the 1.8 snapshots there's a spectate mode (gamemode 3) that renders you invisible and such, and also able to hop into the bodies of other players and mobs to watch from their PoV. And when spectating inside some mobs, shaders are used for various visual effects.
Spider...
Creeper...