1 /*
2 * Copyright (C) 2011 Marek Olšák <maraeo@gmail.com>
3 *
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:
10 *
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
13 * Software.
14 *
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.
22 */
23
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
27 * below.
28 */
29
30 #ifndef FORMAT_R11G11B10F_H
31 #define FORMAT_R11G11B10F_H
32
33 #include <stdint.h>
34
35 #define UF11(e, m) ((e << 6) | (m))
36 #define UF11_EXPONENT_BIAS 15
37 #define UF11_EXPONENT_BITS 0x1F
38 #define UF11_EXPONENT_SHIFT 6
39 #define UF11_MANTISSA_BITS 0x3F
40 #define UF11_MANTISSA_SHIFT (23 - UF11_EXPONENT_SHIFT)
41 #define UF11_MAX_EXPONENT (UF11_EXPONENT_BITS << UF11_EXPONENT_SHIFT)
42
43 #define UF10(e, m) ((e << 5) | (m))
44 #define UF10_EXPONENT_BIAS 15
45 #define UF10_EXPONENT_BITS 0x1F
46 #define UF10_EXPONENT_SHIFT 5
47 #define UF10_MANTISSA_BITS 0x1F
48 #define UF10_MANTISSA_SHIFT (23 - UF10_EXPONENT_SHIFT)
49 #define UF10_MAX_EXPONENT (UF10_EXPONENT_BITS << UF10_EXPONENT_SHIFT)
50
51 #define F32_INFINITY 0x7f800000
52
f32_to_uf11(float val)53 static inline uint32_t f32_to_uf11(float val)
54 {
55 union {
56 float f;
57 uint32_t ui;
58 } f32 = {val};
59
60 uint16_t uf11 = 0;
61
62 /* Decode little-endian 32-bit floating-point value */
63 int sign = (f32.ui >> 16) & 0x8000;
64 /* Map exponent to the range [-127,128] */
65 int exponent = ((f32.ui >> 23) & 0xff) - 127;
66 int mantissa = f32.ui & 0x007fffff;
67
68 if (exponent == 128) { /* Infinity or NaN */
69 /* From the GL_EXT_packed_float spec:
70 *
71 * "Additionally: negative infinity is converted to zero; positive
72 * infinity is converted to positive infinity; and both positive and
73 * negative NaN are converted to positive NaN."
74 */
75 uf11 = UF11_MAX_EXPONENT;
76 if (mantissa) {
77 uf11 |= 1; /* NaN */
78 } else {
79 if (sign)
80 uf11 = 0; /* 0.0 */
81 }
82 } else if (sign) {
83 return 0;
84 } else if (val > 65024.0f) {
85 /* From the GL_EXT_packed_float spec:
86 *
87 * "Likewise, finite positive values greater than 65024 (the maximum
88 * finite representable unsigned 11-bit floating-point value) are
89 * converted to 65024."
90 */
91 uf11 = UF11(30, 63);
92 } else if (exponent > -15) { /* Representable value */
93 exponent += UF11_EXPONENT_BIAS;
94 mantissa >>= UF11_MANTISSA_SHIFT;
95 uf11 = exponent << UF11_EXPONENT_SHIFT | mantissa;
96 }
97
98 return uf11;
99 }
100
uf11_to_f32(uint16_t val)101 static inline float uf11_to_f32(uint16_t val)
102 {
103 union {
104 float f;
105 uint32_t ui;
106 } f32;
107
108 int exponent = (val & 0x07c0) >> UF11_EXPONENT_SHIFT;
109 int mantissa = (val & 0x003f);
110
111 f32.f = 0.0;
112
113 if (exponent == 0) {
114 if (mantissa != 0) {
115 const float scale = 1.0 / (1 << 20);
116 f32.f = scale * mantissa;
117 }
118 } else if (exponent == 31) {
119 f32.ui = F32_INFINITY | mantissa;
120 } else {
121 float scale, decimal;
122 exponent -= 15;
123 if (exponent < 0) {
124 scale = 1.0f / (1 << -exponent);
125 } else {
126 scale = (float) (1 << exponent);
127 }
128 decimal = 1.0f + (float) mantissa / 64;
129 f32.f = scale * decimal;
130 }
131
132 return f32.f;
133 }
134
f32_to_uf10(float val)135 static inline uint32_t f32_to_uf10(float val)
136 {
137 union {
138 float f;
139 uint32_t ui;
140 } f32 = {val};
141
142 uint16_t uf10 = 0;
143
144 /* Decode little-endian 32-bit floating-point value */
145 int sign = (f32.ui >> 16) & 0x8000;
146 /* Map exponent to the range [-127,128] */
147 int exponent = ((f32.ui >> 23) & 0xff) - 127;
148 int mantissa = f32.ui & 0x007fffff;
149
150 if (exponent == 128) {
151 /* From the GL_EXT_packed_float spec:
152 *
153 * "Additionally: negative infinity is converted to zero; positive
154 * infinity is converted to positive infinity; and both positive and
155 * negative NaN are converted to positive NaN."
156 */
157 uf10 = UF10_MAX_EXPONENT;
158 if (mantissa) {
159 uf10 |= 1; /* NaN */
160 } else {
161 if (sign)
162 uf10 = 0; /* 0.0 */
163 }
164 } else if (sign) {
165 return 0;
166 } else if (val > 64512.0f) {
167 /* From the GL_EXT_packed_float spec:
168 *
169 * "Likewise, finite positive values greater than 64512 (the maximum
170 * finite representable unsigned 10-bit floating-point value) are
171 * converted to 64512."
172 */
173 uf10 = UF10(30, 31);
174 } else if (exponent > -15) { /* Representable value */
175 exponent += UF10_EXPONENT_BIAS;
176 mantissa >>= UF10_MANTISSA_SHIFT;
177 uf10 = exponent << UF10_EXPONENT_SHIFT | mantissa;
178 }
179
180 return uf10;
181 }
182
uf10_to_f32(uint16_t val)183 static inline float uf10_to_f32(uint16_t val)
184 {
185 union {
186 float f;
187 uint32_t ui;
188 } f32;
189
190 int exponent = (val & 0x03e0) >> UF10_EXPONENT_SHIFT;
191 int mantissa = (val & 0x001f);
192
193 f32.f = 0.0;
194
195 if (exponent == 0) {
196 if (mantissa != 0) {
197 const float scale = 1.0 / (1 << 19);
198 f32.f = scale * mantissa;
199 }
200 } else if (exponent == 31) {
201 f32.ui = F32_INFINITY | mantissa;
202 } else {
203 float scale, decimal;
204 exponent -= 15;
205 if (exponent < 0) {
206 scale = 1.0f / (1 << -exponent);
207 }
208 else {
209 scale = (float) (1 << exponent);
210 }
211 decimal = 1.0f + (float) mantissa / 32;
212 f32.f = scale * decimal;
213 }
214
215 return f32.f;
216 }
217
float3_to_r11g11b10f(const float rgb[3])218 static inline uint32_t float3_to_r11g11b10f(const float rgb[3])
219 {
220 return ( f32_to_uf11(rgb[0]) & 0x7ff) |
221 ((f32_to_uf11(rgb[1]) & 0x7ff) << 11) |
222 ((f32_to_uf10(rgb[2]) & 0x3ff) << 22);
223 }
224
r11g11b10f_to_float3(uint32_t rgb,float retval[3])225 static inline void r11g11b10f_to_float3(uint32_t rgb, float retval[3])
226 {
227 retval[0] = uf11_to_f32( rgb & 0x7ff);
228 retval[1] = uf11_to_f32((rgb >> 11) & 0x7ff);
229 retval[2] = uf10_to_f32((rgb >> 22) & 0x3ff);
230 }
231
232 #endif /* FORMAT_R11G11B10F_H */
233