Parallax Textures, Made with Camera Flash
A new method of creating parallax mapping has been demonstrated, which can automatically create the maps from an ordinary photograph.
Parallax mapping is a system by which textures displayed on flat surfaces are give the illusion of 3D depth, extruding out into the viewpoint, and making the object they cover seem more real, shadows changing as the viewpoint moves round it.
3D displacement of surfaces is faked by means of displacing textures both by creating a height map of their protuberance from 3D space and then calculating the angle of that protuberance relative to the angle the observer is looking from.
The new method utilises two photos, taken one after the other. The first is a normal photo, the second, lit by camera flash. Merely analysing the resulting shading patterns can capture the surface's 3D texture.
Mashhuda Glencross and team at the University of Manchester, UK, developed the process. Traditionally this 3D information was captured by a 3D scanner, slowly working round the physical object at a speed if 5 degrees a minute.
At the heart of the technique is the assumption that the brightness of a pixel in the image is related to its depth in the scene. Parts of the surface deep in a crack or pit receive light from a restricted area of the sky, and appear relatively dark.
By contrast, protruding parts of the surface receive more light and appear brighter in a photo.
But the colour of the surface also affects its brightness in a photo. With the same illumination, light-coloured spots appear brighter than dark ones.
Taking a photo using the flash removes that effect. The surface is flooded with light and the camera can record the true colour of every part it can see, even those in cracks and pits.
Software then compares the brightness of every matching pair of pixels in the two images and calculates how much of a pixel's brightness is down to its position, and how much is due to its colour.
To test the realism of the results, the researchers asked 20 volunteers to compare images of a surface made using two photos to versions of the same surface rendered using lasers. The volunteers could not tell the difference.
The new technique is already being used to add depth and realism to the ancient carvings that will appear in Maya Skies - a full-dome digital projection for planetariums that tells the story of the Mayan people. Maya Skies will be released in 2009.