2 * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
24 /* Based on code from The OpenGL Programming Guide / 7th Edition, Appendix J.
25 * Available here: http://www.opengl-redbook.com/appendices/
26 * The algorithm in the book contains a bug though, which is fixed in the code
32 #define UF11(e, m) ((e << 6) | (m))
33 #define UF11_EXPONENT_BIAS 15
34 #define UF11_EXPONENT_BITS 0x1F
35 #define UF11_EXPONENT_SHIFT 6
36 #define UF11_MANTISSA_BITS 0x3F
37 #define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT)
38 #define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT)
40 #define UF10(e, m) ((e << 5) | (m))
41 #define UF10_EXPONENT_BIAS 15
42 #define UF10_EXPONENT_BITS 0x1F
43 #define UF10_EXPONENT_SHIFT 5
44 #define UF10_MANTISSA_BITS 0x1F
45 #define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT)
46 #define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)
48 #define F32_INFINITY 0x7f800000
50 static inline uint32_t f32_to_uf11(float val)
59 /* Decode little-endian 32-bit floating-point value */
60 int sign = (f32.ui >> 16) & 0x8000;
61 /* Map exponent to the range [-127,128] */
62 int exponent = ((f32.ui >> 23) & 0xff) - 127;
63 int mantissa = f32.ui & 0x007fffff;
65 if (exponent == 128) { /* Infinity or NaN */
66 /* From the GL_EXT_packed_float spec:
68 * "Additionally: negative infinity is converted to zero; positive
69 * infinity is converted to positive infinity; and both positive and
70 * negative NaN are converted to positive NaN."
72 uf11 = UF11_MAX_EXPONENT;
81 } else if (val > 65024.0f) {
82 /* From the GL_EXT_packed_float spec:
84 * "Likewise, finite positive values greater than 65024 (the maximum
85 * finite representable unsigned 11-bit floating-point value) are
86 * converted to 65024."
89 } else if (exponent > -15) { /* Representable value */
90 exponent += UF11_EXPONENT_BIAS;
91 mantissa >>= UF11_MANTISSA_SHIFT;
92 uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa;
98 static inline float uf11_to_f32(uint16_t val)
105 int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
106 int mantissa = (val & 0x003f);
112 const float scale = 1.0 / (1 << 20);
113 f32.f = scale * mantissa;
115 } else if (exponent == 31) {
116 f32.ui = F32_INFINITY | mantissa;
118 float scale, decimal;
121 scale = 1.0f / (1 << -exponent);
123 scale = (float) (1 << exponent);
125 decimal = 1.0f + (float) mantissa / 64;
126 f32.f = scale * decimal;
132 static inline uint32_t f32_to_uf10(float val)
141 /* Decode little-endian 32-bit floating-point value */
142 int sign = (f32.ui >> 16) & 0x8000;
143 /* Map exponent to the range [-127,128] */
144 int exponent = ((f32.ui >> 23) & 0xff) - 127;
145 int mantissa = f32.ui & 0x007fffff;
147 if (exponent == 128) {
148 /* From the GL_EXT_packed_float spec:
150 * "Additionally: negative infinity is converted to zero; positive
151 * infinity is converted to positive infinity; and both positive and
152 * negative NaN are converted to positive NaN."
154 uf10 = UF10_MAX_EXPONENT;
163 } else if (val > 64512.0f) {
164 /* From the GL_EXT_packed_float spec:
166 * "Likewise, finite positive values greater than 64512 (the maximum
167 * finite representable unsigned 10-bit floating-point value) are
168 * converted to 64512."
171 } else if (exponent > -15) { /* Representable value */
172 exponent += UF10_EXPONENT_BIAS;
173 mantissa >>= UF10_MANTISSA_SHIFT;
174 uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa;
180 static inline float uf10_to_f32(uint16_t val)
187 int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT;
188 int mantissa = (val & 0x001f);
194 const float scale = 1.0 / (1 << 19);
195 f32.f = scale * mantissa;
197 } else if (exponent == 31) {
198 f32.ui = F32_INFINITY | mantissa;
200 float scale, decimal;
203 scale = 1.0f / (1 << -exponent);
206 scale = (float) (1 << exponent);
208 decimal = 1.0f + (float) mantissa / 32;
209 f32.f = scale * decimal;
215 static inline uint32_t float3_to_r11g11b10f(const float rgb[3])
217 return ( f32_to_uf11(rgb[0]) & 0x7ff) |
218 ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) |
219 ((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
222 static inline void r11g11b10f_to_float3(uint32_t rgb, float retval[3])
224 retval[0] = uf11_to_f32( rgb & 0x7ff);
225 retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff);
226 retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff);