Pinchmaps: textures with customizable discontinuities

We introduce a new texture representation that combines standard bi-linearly interpolated samples, for smoothly varying regions, with customizable discontinuities for sharp boundaries between these regions. It consists in a standard signal texture, plus a second texture we call pinchmap, which encodes discontinuities along generally curved lines; this structure is stored in texture memory as a pair of images and is efficiently interpreted on commodity graphic hardware in the fragment shader. We also present a fully automatic way to compute a pinchmap and signal texture pair from an much higher resolution image. We show that the final effect on the screen is a comparable visual quality, for a fraction of the texture storage cost and a very small impact on performance.