On 22.11.2008 02:00, Brian Paul wrote: > Philipp Klaus Krause wrote: >> In _mesa_compressed_texture_size(), texcompress.c there's lots of code >> similar to the following: >> >> case MESA_FORMAT_RGBA_DXT1: >> /* round up width, height to next multiple of 4 */ >> width = (width + 3) & ~3; >> height = (height + 3) & ~3; >> /* 8 bytes per 4x4 tile of RGB[A] texels */ >> size = width * height / 2; >> /* Textures smaller than 4x4 will effectively be made into 4x4 and >> * take 8 bytes. >> */ >> if (size < 8) >> size = 8; >> return size; >> >> What's the purpose of the if (size < 8) size = 8;? It seems redundant to me. > > IIRC, all DTX blocks are 4x4 texels in size and each such block is > represented by 8 bytes. Images smaller than 4x4 pixels are still stored > in 8-byte 4x4 blocks so we need to allocate that minimum amount of memory. > > -Brian
I think the question was why it would be necessary to explicitly round up the calculated size to 8, since width and height are rounded up already and hence size can't be smaller than 8 anyway (unless height or width would be zero, that is). Roland ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
