/* * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com> * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER * DEALINGS IN THE SOFTWARE. */ /* Copied from EXT_texture_shared_exponent and edited, getting rid of * expensive float math bits too. */ #ifndef RGB9E5_H #define RGB9E5_H #include <assert.h> #include <stdint.h> #include "c99_math.h" #define RGB9E5_EXPONENT_BITS 5 #define RGB9E5_MANTISSA_BITS 9 #define RGB9E5_EXP_BIAS 15 #define RGB9E5_MAX_VALID_BIASED_EXP 31 #define MAX_RGB9E5_EXP (RGB9E5_MAX_VALID_BIASED_EXP - RGB9E5_EXP_BIAS) #define RGB9E5_MANTISSA_VALUES (1<<RGB9E5_MANTISSA_BITS) #define MAX_RGB9E5_MANTISSA (RGB9E5_MANTISSA_VALUES-1) #define MAX_RGB9E5 (((float)MAX_RGB9E5_MANTISSA)/RGB9E5_MANTISSA_VALUES * (1<<MAX_RGB9E5_EXP)) static inline int rgb9e5_ClampRange(float x) { union { float f; uint32_t u; } f, max; f.f = x; max.f = MAX_RGB9E5; if (f.u > 0x7f800000) /* catches neg, NaNs */ return 0; else if (f.u >= max.u) return max.u; else return f.u; } static inline uint32_t float3_to_rgb9e5(const float rgb[3]) { int rm, gm, bm, exp_shared; uint32_t revdenom_biasedexp; union { float f; uint32_t u; } rc, bc, gc, maxrgb, revdenom; rc.u = rgb9e5_ClampRange(rgb[0]); gc.u = rgb9e5_ClampRange(rgb[1]); bc.u = rgb9e5_ClampRange(rgb[2]); maxrgb.u = MAX3(rc.u, gc.u, bc.u); /* * Compared to what the spec suggests, instead of conditionally adjusting * the exponent after the fact do it here by doing the equivalent of +0.5 - * the int add will spill over into the exponent in this case. */ maxrgb.u += maxrgb.u & (1 << (23-9)); exp_shared = MAX2((maxrgb.u >> 23), -RGB9E5_EXP_BIAS - 1 + 127) + 1 + RGB9E5_EXP_BIAS - 127; revdenom_biasedexp = 127 - (exp_shared - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS) + 1; revdenom.u = revdenom_biasedexp << 23; assert(exp_shared <= RGB9E5_MAX_VALID_BIASED_EXP); /* * The spec uses strict round-up behavior (d3d10 disagrees, but in any case * must match what is done above for figuring out exponent). * We avoid the doubles ((int) rc * revdenom + 0.5) by doing the rounding * ourselves (revdenom was adjusted by +1, above). */ rm = (int) (rc.f * revdenom.f); gm = (int) (gc.f * revdenom.f); bm = (int) (bc.f * revdenom.f); rm = (rm & 1) + (rm >> 1); gm = (gm & 1) + (gm >> 1); bm = (bm & 1) + (bm >> 1); assert(rm <= MAX_RGB9E5_MANTISSA); assert(gm <= MAX_RGB9E5_MANTISSA); assert(bm <= MAX_RGB9E5_MANTISSA); assert(rm >= 0); assert(gm >= 0); assert(bm >= 0); return (exp_shared << 27) | (bm << 18) | (gm << 9) | rm; } static inline void rgb9e5_to_float3(uint32_t rgb, float retval[3]) { int exponent; union { float f; uint32_t u; } scale; exponent = (rgb >> 27) - RGB9E5_EXP_BIAS - RGB9E5_MANTISSA_BITS; scale.u = (exponent + 127) << 23; retval[0] = ( rgb & 0x1ff) * scale.f; retval[1] = ((rgb >> 9) & 0x1ff) * scale.f; retval[2] = ((rgb >> 18) & 0x1ff) * scale.f; } #endif