/* * Copyright (C) 2011 Marek Olšák * * 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. */ /* Based on code from The OpenGL Programming Guide / 7th Edition, Appendix J. * Available here: http://www.opengl-redbook.com/appendices/ * The algorithm in the book contains a bug though, which is fixed in the code * below. */ #include #define UF11(e, m) ((e << 6) | (m)) #define UF11_EXPONENT_BIAS 15 #define UF11_EXPONENT_BITS 0x1F #define UF11_EXPONENT_SHIFT 6 #define UF11_MANTISSA_BITS 0x3F #define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT) #define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT) #define UF10(e, m) ((e << 5) | (m)) #define UF10_EXPONENT_BIAS 15 #define UF10_EXPONENT_BITS 0x1F #define UF10_EXPONENT_SHIFT 5 #define UF10_MANTISSA_BITS 0x1F #define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT) #define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT) #define F32_INFINITY 0x7f800000 static inline uint32_t f32_to_uf11(float val) { union { float f; uint32_t ui; } f32 = {val}; uint16_t uf11 = 0; /* Decode little-endian 32-bit floating-point value */ int sign = (f32.ui >> 16) & 0x8000; /* Map exponent to the range [-127,128] */ int exponent = ((f32.ui >> 23) & 0xff) - 127; int mantissa = f32.ui & 0x007fffff; if (exponent == 128) { /* Infinity or NaN */ /* From the GL_EXT_packed_float spec: * * "Additionally: negative infinity is converted to zero; positive * infinity is converted to positive infinity; and both positive and * negative NaN are converted to positive NaN." */ uf11 = UF11_MAX_EXPONENT; if (mantissa) { uf11 |= 1; /* NaN */ } else { if (sign) uf11 = 0; /* 0.0 */ } } else if (sign) { return 0; } else if (val > 65024.0f) { /* From the GL_EXT_packed_float spec: * * "Likewise, finite positive values greater than 65024 (the maximum * finite representable unsigned 11-bit floating-point value) are * converted to 65024." */ uf11 = UF11(30, 63); } else if (exponent > -15) { /* Representable value */ exponent += UF11_EXPONENT_BIAS; mantissa >>= UF11_MANTISSA_SHIFT; uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa; } return uf11; } static inline float uf11_to_f32(uint16_t val) { union { float f; uint32_t ui; } f32; int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT; int mantissa = (val & 0x003f); f32.f = 0.0; if (exponent == 0) { if (mantissa != 0) { const float scale = 1.0 / (1 << 20); f32.f = scale * mantissa; } } else if (exponent == 31) { f32.ui = F32_INFINITY | mantissa; } else { float scale, decimal; exponent -= 15; if (exponent < 0) { scale = 1.0f / (1 << -exponent); } else { scale = (float) (1 << exponent); } decimal = 1.0f + (float) mantissa / 64; f32.f = scale * decimal; } return f32.f; } static inline uint32_t f32_to_uf10(float val) { union { float f; uint32_t ui; } f32 = {val}; uint16_t uf10 = 0; /* Decode little-endian 32-bit floating-point value */ int sign = (f32.ui >> 16) & 0x8000; /* Map exponent to the range [-127,128] */ int exponent = ((f32.ui >> 23) & 0xff) - 127; int mantissa = f32.ui & 0x007fffff; if (exponent == 128) { /* From the GL_EXT_packed_float spec: * * "Additionally: negative infinity is converted to zero; positive * infinity is converted to positive infinity; and both positive and * negative NaN are converted to positive NaN." */ uf10 = UF10_MAX_EXPONENT; if (mantissa) { uf10 |= 1; /* NaN */ } else { if (sign) uf10 = 0; /* 0.0 */ } } else if (sign) { return 0; } else if (val > 64512.0f) { /* From the GL_EXT_packed_float spec: * * "Likewise, finite positive values greater than 64512 (the maximum * finite representable unsigned 10-bit floating-point value) are * converted to 64512." */ uf10 = UF10(30, 31); } else if (exponent > -15) { /* Representable value */ exponent += UF10_EXPONENT_BIAS; mantissa >>= UF10_MANTISSA_SHIFT; uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa; } return uf10; } static inline float uf10_to_f32(uint16_t val) { union { float f; uint32_t ui; } f32; int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT; int mantissa = (val & 0x001f); f32.f = 0.0; if (exponent == 0) { if (mantissa != 0) { const float scale = 1.0 / (1 << 20); f32.f = scale * mantissa; } } else if (exponent == 31) { f32.ui = F32_INFINITY | mantissa; } else { float scale, decimal; exponent -= 15; if (exponent < 0) { scale = 1.0f / (1 << -exponent); } else { scale = (float) (1 << exponent); } decimal = 1.0f + (float) mantissa / 32; f32.f = scale * decimal; } return f32.f; } static inline uint32_t float3_to_r11g11b10f(const float rgb[3]) { return ( f32_to_uf11(rgb[0]) & 0x7ff) | ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) | ((f32_to_uf10(rgb[2]) & 0x3ff) << 22); } static inline void r11g11b10f_to_float3(uint32_t rgb, float retval[3]) { retval[0] = uf11_to_f32( rgb & 0x7ff); retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff); retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff); }