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
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)
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)
46 #define F32_INFINITY 0x7f800000
48 static inline unsigned f32_to_uf11(float val
)
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;
63 if (exponent
== 128) { /* Infinity or NaN */
64 /* From the GL_EXT_packed_float spec:
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."
70 uf11
= UF11_MAX_EXPONENT
;
79 } else if (val
> 65024.0f
) {
80 /* From the GL_EXT_packed_float spec:
82 * "Likewise, finite positive values greater than 65024 (the maximum
83 * finite representable unsigned 11-bit floating-point value) are
84 * converted to 65024."
88 else if (exponent
> -15) { /* Representable value */
89 exponent
+= UF11_EXPONENT_BIAS
;
90 mantissa
>>= UF11_MANTISSA_SHIFT
;
91 uf11
= exponent
<< UF11_EXPONENT_SHIFT
| mantissa
;
97 static inline float uf11_to_f32(uint16_t val
)
104 int exponent
= (val
& 0x07c0) >> UF11_EXPONENT_SHIFT
;
105 int mantissa
= (val
& 0x003f);
111 const float scale
= 1.0 / (1 << 20);
112 f32
.f
= scale
* mantissa
;
115 else if (exponent
== 31) {
116 f32
.ui
= F32_INFINITY
| mantissa
;
119 float scale
, decimal
;
122 scale
= 1.0f
/ (1 << -exponent
);
125 scale
= (float) (1 << exponent
);
127 decimal
= 1.0f
+ (float) mantissa
/ 64;
128 f32
.f
= scale
* decimal
;
134 static inline unsigned f32_to_uf10(float val
)
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;
149 if (exponent
== 128) {
150 /* From the GL_EXT_packed_float spec:
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."
156 uf10
= UF10_MAX_EXPONENT
;
165 } else if (val
> 64512.0f
) {
166 /* From the GL_EXT_packed_float spec:
168 * "Likewise, finite positive values greater than 64512 (the maximum
169 * finite representable unsigned 10-bit floating-point value) are
170 * converted to 64512."
174 else if (exponent
> -15) { /* Representable value */
175 exponent
+= UF10_EXPONENT_BIAS
;
176 mantissa
>>= UF10_MANTISSA_SHIFT
;
177 uf10
= exponent
<< UF10_EXPONENT_SHIFT
| mantissa
;
183 static inline float uf10_to_f32(uint16_t val
)
190 int exponent
= (val
& 0x03e0) >> UF10_EXPONENT_SHIFT
;
191 int mantissa
= (val
& 0x001f);
197 const float scale
= 1.0 / (1 << 20);
198 f32
.f
= scale
* mantissa
;
201 else if (exponent
== 31) {
202 f32
.ui
= F32_INFINITY
| mantissa
;
205 float scale
, decimal
;
208 scale
= 1.0f
/ (1 << -exponent
);
211 scale
= (float) (1 << exponent
);
213 decimal
= 1.0f
+ (float) mantissa
/ 32;
214 f32
.f
= scale
* decimal
;
220 static inline unsigned float3_to_r11g11b10f(const float rgb
[3])
222 return ( f32_to_uf11(rgb
[0]) & 0x7ff) |
223 ((f32_to_uf11(rgb
[1]) & 0x7ff) << 11) |
224 ((f32_to_uf10(rgb
[2]) & 0x3ff) << 22);
227 static inline void r11g11b10f_to_float3(unsigned rgb
, float retval
[3])
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);