Complex sentence: The first known record of projections onto walls was in 1969, when Disneyland opened their Haunted Mansion ride using fake disembodied heads as objects which had 16mm film projected onto them to make them look real through optical illusions.
Split into simpler sentences: The first known record of projections onto walls was in 1969, when Disneyland opened their Haunted Mansion ride. They used fake disembodied heads as objects which had 16mm film projected onto them to make them look real through optical illusions.