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Projection Mapping (3D)
About this app
A projector shines onto a room corner, a column, a sculpture of blocks or a facade. Four modes, uncorrected, keystone, mapping and illusion, show why keystone correction holds on one plane only, mapping fits every shape and a spatial illusion works only from the sweet spot. A panel shows the image the projector sends; lenses show brightness (cos θ / d²) and stretched pixels.
Frequently asked questions
- What is projection mapping?
- Projection mapping projects images precisely onto non-flat objects such as building facades, sculptures or stage sets. A 3D model or survey of the surface tells the system which projector pixel lands on which point, and the outgoing image is pre-distorted so the content sits on the surface. It helps to think of the projector as a camera in reverse: each pixel becomes a ray of light that lands on the first surface it hits.
- Why isn’t keystone correction enough for facades or room corners?
- Keystone correction pre-distorts the image so that it looks rectangular on exactly one plane. A room corner, a column or a facade with projections is made of several planes or curved surfaces, and the image stays distorted on every surface except the reference plane. Mapping binds the content to the geometry of each surface, so it looks right from any viewpoint.
- How does projection brightness depend on distance and angle?
- Illuminance on the surface is proportional to cos θ / d², where d is the distance to the projector and θ the angle between the light ray and the surface normal. Doubling the distance gives a quarter of the brightness, and at 60° incidence it halves. At grazing angles the pixels are also stretched, so the image looks dimmer and softer there.
- What can I try out in this app?
- Choose a projection object (room corner, column, sculpture of blocks or facade) and some content, then switch between the uncorrected, keystone, mapping and illusion modes. A panel shows the image the projector actually sends, and the brightness and pixel lenses colour the surface by cos θ / d² and by pixel stretch. Projector and viewer can be dragged in the scene; in illusion mode you can see that the depth only works from the sweet spot.
Subject: Architecture & scenography
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