(The Eurographics Association, 2007) Stroem, Jacob; Pettersson, Martin; Mark Segal and Timo Aila
We present a novel texture compression system for improved image quality. Building on the iPACKMAN/ETC method, bit combinations that are invalid in that system are used to allow for three additional decompression modes without increasing the bit rate. These modes increase quality, especially for color edges and blocks with smoothly varying content. Due to the use of invalid bit combinations, the system, called ETC2, is backwards compatible with iPACKMAN/ETC. It outperforms S3TC/DXTC and iPACKMAN/ETC in terms of PSNR with 0.8 dB and 1.0 dB respectively, which is clearly visible to the human eye.
(The Eurographics Association, 2007) Munkberg, Jacob; Olsson, Ola; Stroem, Jacob; Akenine-Moeller, Tomas; Mark Segal and Timo Aila
We present a new powerful and flexible fixed-rate normal map compression algorithm with higher quality than existing schemes on a test suite of normal maps. Our algorithm encodes a tight box with uniform normals inside the box, and in addition, a special mode is introduced for handling slowly varying normals. We also discuss several error measures needed to understand the qualities of different algorithms. We believe the high quality of our technique makes it a potential candidate for inclusion in OpenGL ES.