There are two principal ways of approaching a video-mapping show:
1)-Project images on a surface/façade. Images are projected in the “normal” way, as if the building were a huge flat screen.
2)MASKING. It consists on creating masks (a sort of opacity templates) with the exact shape and position of the different elements of the building/architecture etc. On this masks, or in the space between this masks, is where the video is projected, using a simple alpha-channel technique. This produces the illusion that some parts of the building glow, darken etc.