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